Desert Plants

Desert Plants
Desert Plants
Volume 23, Number 1
June 2007
Zygophyllum on coastal dunes near Bqaiq
Electronic Field Guide to the Plants of Popular Recreation Sites in Arizona's
Sonoran Desert, William Theodore Johnson
The Outstanding Stamens of Pennisetum clandestinum, Kathryn Mauz
Book Reviews, Margaret Norem
Preliminary Findings of the Southwest Monarch Study, C.L. Kline
Arabian Desert Primer: Ornamental Potential of Hyper-arid Adapted Plants
from Saudi Arabia, Jeffrey M. Petrie
Desert Plants
Desert Plants
Volume 23, Number 1, June 2007
A journal devoted to broadening knowledge of plants
indigenous or adapted to arid and sub-arid regions and to
encouraging the appreciation of these plants.
Published by The University of Arizona for the
Boyce Thompson Southwestern Arboretum
37615 E. Highway 60
Superior, Arizona 85273-5100
Margaret A. Norem, Editor
2120 E. Allen Road
Tucson, Arizona 85719
(520) 623-3868 3t ~ ·1t.N~
Copyright 2007
The Arizona Board of Regents on behalf of
The University of Arizona
The Boyce Thompson Southwestern Arboretum at Superior,
Arizona is cooperatively managed by the Arizona State Parks
Board, Boyce Thompson Sourthwestern Arboretum, Inc., and
The University of Arizona.
Underwriters 2007
Animas Foundation
Arid Zone Trees
Josiah T. Austin
Conrad Bahre
Colossal Cave Mountain Park
Desierto Verde
Frank W. Ellis
Michal J. Glines
Harris Environmental Group
Mary & Gary Irish
Matthew B. Johnson & Patricia A. Rorabaugh
Mr. & Mrs. Greayer Mansfield-Jones
Michael McNulty
Joseph A. Meeker
Lee J. Miller
Victor J. Miller
Mountain States Wholesale Nursery
Nancy Norem
Robert B. Pape
John W. Pierce
R.T. Ramage
Dean & Will Anne Ricer
Mark & Jane Siegwarth
R. Linwood Smith
Keith Taylor
Michele Timmons & Clayton May
Tom Wootten. T & E Inc.
Brett G. Woywood
Supporters 2007
Emeline M. Angevine
Jeanne Bensema
Louis Biagi
Cass Blodgett
John M. Bridges
Bronson Joy Brown
Jack Carter
Robert D. Cross
Desert Ag Services
Mary Peace Douglas
Theodore Esslinger
Kay Fowler
Thomas A. Friedlander
Brooke Gebow
Herbert and Mary Hull
R. Roy Johnson and Lois T. Haight
Vernon L. and Diane R. Kliewer
Bill Little
James P. Mandaville
Chris Marshall
PaulS. Martin
Brian McCarthy and Judith Gray
Edwin Minch
Elizabeth Moody
Douglas R. Newton
Ken Pavlicek
John H. Rumely
Harley G. Shaw
David Steadman
James R. Youse
Field Guide
Electronic Field Guide to the
Plants of Popular Recreation
Sites in Arizona's So nor an
William Theodore Johnson
P.O. Box 30731
Mesa, Arizona 85275
Field guides occupy the intersection of plants and
people. Improving the user's understanding of nature,
plant field guides have the potential of increasing
the satisfaction of their outdoor experience. A more
satisfied field guide user is more likely to take action
to preserve places where native plants grow.
Unfortunately, print field guides are either too technical
or incomplete, resulting in frustration rather than
satisfaction. Most offer no systematic method where
a user may identify an unknown plant based on
observable characteristics, relying instead on randomly
browsing through a series of illustrations in the hope
that a static photo or drawing will resemble the plant
in question. Picture-book taxonon1y is unreliable
when the geographic area under consideration is
large and the vegetation diverse. Arizona, especially
its Sonoran Desert is such an environment, where
sporadic precipitation fosters the unreliable occurrence
of annuals and species with unusual growth forms,
which may not be included in field guides to the
Southwest, West, or North An1erica. Print field guides,
which include all known plants to small, isolated
geographic areas such as popular parks is simply not
cost effective.
Electronic field guides are not constrained by these
econon1ic lilnitations and they offer a superior n1ethod
of identifying plants. With an eye to the future where
dynamic, interactive features become the norm for high
tech users packing portable electronic devices over hill
and dale, this article introduces a novel field guide to
plants using standard spreadsheet software. Based on
floras produced by graduate students and others for 12
popular recreation sites near large population centers,
this E-guide offers a fast, reliable, non-technical tool for
large numbers of outdoor enthusiasts to identify plants
in areas they already visit and enjoy.
Print Field Guide Survey
Identification Metlzods
A survey of selected non-technical plant field guides
is quite revealing (Table 1). Not all such guides are
created equal, but most suffer from the same
shortcomings. Surprisingly, few offer any systematic
or rational tool, whereby a non-specialist could pick
it up and identify an unknown plant by following a
logical sequence of steps. Instead, most present a series
of static illustrations that the user is supposed to match
to the plant in question. The problems with such an
approach are in1mediately apparent. What if the plant
in question is not at the same stage of development
as the one illustrated? The illustrations usually rely
heavily on colorful flowers for herbaceous plants and
leaves for woody species. However, anytime you focus
on an illustration, rather than a description you run
the risk of being mislead by superficial resemblances.
Illustrations should validate the identification not
determine it. Dichotomous keys are often used in an
attempt to solve this problem.
Plant keys, long considered a tried and true method
of identifying plants, suffer from their own set of
shortcomings. The vast majority are far too technical for
the average outdoor enthusiast who lacks specialized
training in plant morphology and its associated
jargon. Additionally, plant characteristics used in the
key may be quite difficult to determine, even when
the characteristic is relatively well understood. For
exan1ple, the choice between evergreen and deciduous
is often presented. Unfortunately, at the height of the
growing season, when most people find themselves
confronted with such a choice, they will not be able
to make the distinction. Keys work for botanists with
experience and specialized training in what to look for
on an herbarium sheet as well as in the field. Randomly
browsing illustrations or pouring over detailed and
technical couplets in a dichotomous key lie at opposite
ends of the spectrum of tools offered in plant field
guides. Both extremes suffer from a deeper issue or
shortcon1ing, that of which plants are included in the
specific guide in the first place.
Plant field guides offered in print cover large
geographic areas: states, regions, or continents.
Individuals using these guides will encounter a wide
variety of plants. Accurate field guides must introduce
significant technical aspects or n1ake cuts in the plants
they n1ight include. Econon1ic considerations favor
the latter strategy. Consequently, n1any field guides
include only trees, cacti, or wildflowers. Others focus
on certain elevational boundaries or habitats such as
deserts. In any case, subjective choices are made as to
Desert Plants
what plants to include. Plants considered common,
conspicuous, desirable, or obnoxious, like vegetative
celebrities are most often featured on the pages of plant
field guides. Even those field guides which focus on
one class of organism like trees, are always incomplete
in their coverage. Users of such guides must make
distinctions between the plants growing where they are
and those growing far away. Economic considerations
prohibit the profitability of publishing a print guide to
the plants of the Superstition Wilderness for example.
However, if a hiker encountered a tree there, it would
be much easier to sort out its identity from other trees
in the Superstitions rather than trees in the next State.
E-Guides do not suffer from such economic or
geographic limitations.
While print field guides fail to include species that fall
within their scope, the extent of their failure to include
certain species varies widely. Using trees as a convenient
medium of comparison between the proposed E-Guide
at the end of the Table 1 and selected print guides, we
find that the percentages of species excluded varies
from 95% (Fandex) to 15% (Peterson's). The percentage
of species not included in each relevant print guide
is listed under the name of the guide in Table 1. The
tendency of field guides to limit their scope to specific
organisms such as trees also contributes to a sense of
intellectual isolation. Not only do print field guides
exclude species that lie within their scope, they also
fail to encompass broad practical elements that might
make them more useful such as a trail guide to where
the plants occur in their native surroundings.
Generalists interested in everything they encounter
from plants to animals to rocks n1ust purchase and carry
many guides. The burden of the expense and bulk are
obviously prohibitive. Consumers also make choices
and which guides to exclude from their collections is
one choice. The individual trying to identify a plant
that is not even included in their guide is faced with
certain frustration.
Most print field guides are designed as "one size fits
all." They are static. Each tin1e the user picks one up,
they will start at the beginning and go through the
same steps. Each time a yellow flowered plant is to
be identified, they will turn to the section for yellow
and start flipping through the illustrations to find a
match. Each time a tree with simple leaves is found,
they will start keying from that point. Unfortunately,
depending on the person, the plant, and the place, it
may be appropriate to start with flowers today but
leaves tomorrow. Print guides do not offer this sort of
dynamic flexibility.
An E-Guide Story of Development
Surprisingly, an electronic field guide using standard
spreadsheet software, resolves all of the shortcomings
associated with print field guides listed here.
Additionally, a number of other advantages have
surfaced, not the least of which is compatibility with
the broader trend within society toward the use of
electronic approaches to tasks previously associated
with paper-based products and processes. However,
electronic field guides are not without their own set
of challenges, making their full acceptance a gradual
process as the human - machine interface is held in
lower esteem than the human - print interface.
Having created an electronic version of a dichotomous
key using a standard Web browser, I sought an
alternative approach to developing an electronic tool
for identifying plants, one that could be easily updated
as new species were added, names changed, or other
n1odifications becan1e necessary. After consulting with
a trainer of various desktop applications, relational
databases such as Access were ruled out. Spreadsheet
software was suggested by this trainer who worked
with both novice and experienced computer users. Excel
was selected due to its availability and widespread
use among PC users. The auto-filter function (see the
instructions in Appendix 1) allows the user to sort
on any combinations of characters quickly and in a
dynamic fashion, different each time an identification
is attempted.
Popular recreation areas were matched with available
plant checklists produced from floristic studies at
Arizona State University (2006). Twelve pre-defined
checklists were selected from SEINET (The Southwest
Environmental Inforn1ation Network), including the
Maricopa County Parks, Superstitions, Seven Springs,
Organ Pipe Cactus National Monument, Castle Dome
Mountains, and South Mountain. Plants readily
identifiable and continually available were selected
using the growth habit information on the Plants
National Database (US Department of Agriculture
2006). This includes sub-shrubs, shrubs, trees, cacti,
vines, woody grasses, epiphytes, and yucca-like plants.
Herbaceous plants have not yet been included due to
the spotty nature of their appearance depending on a
variety of irregular and unpredictable environmental
factors. Their appearance is quite seasonal and typically
quite brief. Successful field identification of plants
begins with a complete list of plants and plants that
will be encountered throughout the year, regardless of
local environmental conditions.
A master list of plants was created, identifying the
species found in each area. Common plants are defined
as those which occur in more than half of the areas
Field Guide
listed (seven areas). They are indicated by red text.
Each group (cacti, epiphytes, woody grasses, yuccalike plants, and vines) were shaded differently on
the master list and in the section marked by a tab for
each group. Woody plants (sub-shrubs, shrubs, and
trees) constituted the largest group and they were left
unshaded. A glossary defines plant families, plant
characteristics, and the geographic areas included.
Tabs were created for each group and a series of nontechnical characteristics set at the head of each column.
The characteristics used varies with each group. For
example, spine characteristics are used for cacti, leaf
characteristics for the woody plants, flower color for
all groups, and specific distinctives applicable for each
species conclude the series of characteristics used.
Columns for the area where the plant was found, family,
and common names were also created. A variety of
sources were consulted for this information including
Shreve and Wiggins (1964), Kearney and Peebles (1960),
and the Jepson Online Manual (University of Califonlia
Berkeley 2006).
This E-Guide offers a number of advantages over
traditional print guides in addition to those already
stated. This electronic file is free, easy to share, easy to
update, and expandable to include a variety of natural
elements of interest to particular users such as rocks or
animals. It can also be distributed with trail guides to
the areas included, making it more of a comprehensive
approach to enjoying and learning about the natural
Contrary to convention in the print realm, illustrations
in the E-Guide are used to validate the identification,
not determine it. The goal is to have the user look
at the plant, critically and carefully. There is no
substitute for a careful examination of a specin1en.
Casually matching plant with illustration is more
often associated with carelessness and inaccurate
identifications. This E-Guide includes nearly 1,000
images linked to various Internet sites, prin1arily
from SEINET (Arizona State University 2006), Plants
National Database (US Department of Agriculture
2006), and CalPhotos (University of California
Berkeley 2006).
No electronic product is without its bugs. While not a
bug, the future acceptability of such a novel field guide
has yet to be determined. One of the challenges to its
use is the version of Excel used to operate the guide
versus the version used to create it. Incon1patibilities
are possible. The manner in which the file is used will
also affect its performance. If the Excel file is used
within a Web browser, it performs differently than if
it is used only in Excel. Use within Excel only rather
than within a Web browser is recommended. Finally,
to view the illustrations, a link to the Internet is
A library card catalog offers a reliable example of a
transition from print to electronic formats. It has taken a
generation of users to fully accept the electronic format
of library catalogs. Electronic field guides may require
a similar time frame to find general acceptance. Who
would expect or desire to go back to the card catalog
in a library? One day the same will be said of print
field guides.
Demonstrations of this guide have been made in a
variety of settings, such as public library programs and
adult education classes at Mesa Community College. In
each setting, the Excel file has been freely distributed to
interested parties. It has also been given to high school
biology students with favorable feedback. Testing is
ongoing. Free copies of the file are available from the
author at, or PO Box 30731,
Mesa, AZ 85275.
Based on initial feedback, theE-Guide described herein
has the potential of radically changing how we identify
plants in the field. Its simple design, use of standard
software, low production cost, and ease of use make
it a strong competitor with print guides. Based on the
user's ability to successfully identify a specimen with
each guide in the shortest time, this guide outperforms
print guides currently available.
Future developments will focus on the creation of a
sin1ilar guide to Arizona's mountain recreation sites
such as Chiricahua National Monument, the Sierra
Anchas, Pinal Mountains, the Grand Canyon, and San
Francisco Peaks. This guide will include herbaceous
annuals and perennials. A third file is also being created
for cultivated plants in the Valley of the Sun (Phoenix).
Ethnobotanical information is currently available with
the desert file. Landscape information could be added
to the file on cultivated plants.
Electronic field guides have yet to assume their final
form. Several versions are available and others are
under development. Regardless of the form they take,
now is the time to explore the options, test the lin1its,
and discover the best means to identify specimens in
the field accurately, quickly, and easily for novice and
expert alike.
Desert Plants
Arizona Rare Plant Committee. 200 I. Arizona Rare Plant
Field Guide. Arizona: Arizona Rare Plant Committee.
Arizona State University. 2006. Interactive Flora of South
Mountain Park, Phoenix, Arizona, USA, America's Largest Municipal Park. Online. Access: http://seinet.asu.
edu/navikey/SouthMountainlndex.jsp, II October 2006.
Arizona State University. 2006. Southwest Environmental
Information Network. Online. Access: <http://seinet.asu.
edu/>, 11 October 2006.
Amberger, Leslie P. 1982. Flowers of the Southwest Mountains. Tucson, AZ: Southwest Parks and Monuments
Aronson, Steven M. L. 1998. Fandex Family Field Guides:
Trees. NY: Workman.
Benson, Lyman. 1981. The Cacti of Arizona, revised 3r<~ edition. Tucson, AZ: University of Arizona Press.
Benson, Lyman and Robert A. Darrow. 1981. Trees and
Shrubs of the Southwestern Deserts. Tucson, AZ: University of Arizona Press.
Bowers, Janice Emily. 1987. One-hundred Roadside Wildflowers. Tucson, AZ: Southwest Parks and Monuments
Bowers, Janice Emily. 1989. One-hundred Desert Wildflowers. Tucson, AZ: Southwest Parks and Monuments
Correll, Donovan S. and Helen B. Correll. 1975. Aquatic
and Wetland Plants of Southwestern United States (2
volumes). Stanford, CA: Stanford University Press.
DeGraaf, Richard M. and Paul E. Sendak. 2006. Native and
naturalized Trees ofNew England and Adjacent Canada: A
Field Guide. London: University Press of New England.
Dodge, Natt N. 1985. Flowers ofthe Southwest Deserts. Tucson, AZ: Southwest Parks and Monuments Association.
Earle, W. Hubert. 1990. Cacti of the Southwest (revised with
color, 3rd printing). Tempe, AZ: Rancho Arroyo Book
Elmore, Francis H. 1976. Shrubs and Trees ofthe Southwest
Uplands. Tucson, AZ: Southwest Parks and Monuments
Engard, Rodney G. 1989. The Flowering Southwest. Tucson,
AZ: Great Impressions.
Epple, Anne Orth. 1995. Plants of Arizona. Helena. MT:
Fischer, Pierre C. 1989. Seventy Common Cacti. Tucson. AZ:
Southwest Parks and Monuments Association.
Hitchcock. A.S. 1971. Manual of the Grasses of the United
States (2 volumes. 2nd edition revised by Agnes Chase).
NY: Dover.
Kearney. Thomas H. , Robert H. Peebles, and Collaborators (2"<~ edition with supplement by J.T. Howell, E.
McClintock, and collaborators) 1960. Arizona Flora.
Berkeley, CA: University of California Press.
Lamb, Samuel II. 19S9. Woody Plants of the Southwest.
Santa Fe. NM: Sunstone Press.
Lawrence, Anna and William Hawthorne. 2006. Plant
Identification: Creating User-friendly Field Guides for
Biodiversity Management. London: Earthscan.
Lehr, J. Harry. 197S. A Catalog of the Flora of Arizona.
Phoenix, AZ: Desert Botanical Garden.
McDougall, W.B. 1973. Seed Plants of Northern Arizona.
Flagstaff, AZ: The Museum of Northern Arizona.
Miller. Millie and Cyndi Nelson. 1996. Desert Critters
- Plants and Animals of the Southwest. Boulder, CO:
Johnson Books.
Nabhan, Gary Paul, Mary Irish, Jane Cole, and James R.
Metcalf (eds.). 19SS. Desert Wildflowers. Phoenix, AZ:
Arizona Highways Magazine.
Petrides. George A. 1992. Peterson Field Guides: Western
Trees. NY: Houghton Mifflin Co.
Preston, Richard J. 1968. Rocky Mountain Trees, third revised edition. NY: Dover.
Quinn, Meg. 2000. Wildflowers of the Desert Southwest.
Tucson, AZ: Rio Nuevo Publishers.
Rushforth. Keith and Charles Hollis. 2006. Field Guide to
the Trees of North America. Washington, DC: National
Geographic Society.
Sargent, Charles Sprague. 1965. Manual of the Trees ofNorth
America (2 volumes). NY: Dover.
Shreve, Forrest and Ira L. Wiggins. 1964. Vegetation and
Flora of the Sonoran Desert (2 volumes). Stanford, CA:
Stanford University Press.
Stubbcndieck, James, Stephan L. Hatch, and L.M. Landholt.
2003. North American Wildland Plants, A Field Guide.
Lincoln, NE: University of Nebraska Press.
University of California. Berkeley. 2006. CalPhotos. Online.
Access: <>, II October
University of California. Berkeley. 2006. Jepson Manual.
Online. Access:
<http://ucjeps. treat indexes.
html>, II October 2006.
Urban Landscape Committee. 1990. Desert Trees. Tucson,
AZ: Arizona Native Plant Society.
Urban Landscape Committee. 1991. Desert Wildflowers.
Tucson, AZ: Arizona Native Plant Society.
Urban Landscape Committee. 1991. Desert Ground Covers
and Vines. Tucson, AZ: Arizona Native Plant Society.
Urban Landscape Committee. 1992. Desert Accent Plants.
Tucson, AZ: Arizona Native Plant Society.
Urban Landscape Committee. 1993. Desert Grasses. Tucson,
AZ: Arizona Native Plant Society.
US Department of Agriculture. 2006. Plants National
Database. Online. Access: <>,
11 October 2006.
Field Guide
Tips for First-time Users:
Electronic Field Guide to the
Plant's ofPopular Recreation Sites
in Arizona's Sonoran Desert
Step by Step Guide & Principles
Step One
Start by opening Excel then the ..desflora" file in the top
directory on this CD. AS with most computer programs, there
is more than one way to accomplish this task. You could go
through .. My Computer" or the Windows Explorer program
to open this file. It doesn't really matter how you open the
file. but it is important for you to open it so it runs in Excel
not and Internet browser so the images open properly.
Step Two
Determine which group the plant belongs in: Trees/Shrubs.
Cacti. Vines, etc. as listed at the bottom of the spread sheet
(Figure 1). Take note of the plant's attributes as appropriate
for the group: leaves/flowers for trees and shrubs. spines
for cacti, etc. If you are unsure what these terms mean.
check the glossary (another tab at the bottom of the sheet).
Currently, herbaceous plants are not included (wildflowers,
ferns, weeds).
Click on ··nata" in the menu bar and select ••filter" then
.. Autofilter". Notice the drop down arrows at the top of each
column. By clicking on these drop down arrows. you will be
able to select from a specific range of attributes. eliminating
others from consideration.
Step Three
This guide is location (Place) driven. Use it in association
with hiking, biking. and other recreation activities in the
popular sites included (Figure 2). Note the text in red
indicates a ..common" plant. one which occurs in over half
of the areas included.
I recommend that you start with the location column. lfyou
know the plant family. you could use that next. but more
than likely, you wilJ use available attributes for the plant in
question. You are not restricted to any specific attribute like
most print guides. based solely on flower color. Here, you
can proceed with only leaves and in the arid Soutwest, that
is important.
For illustration purposes. let's start with South Mountain
trees and shrubs.
Step Four
Now select a plant attribute, such as leaves simple/divided
or alternate/opposite/whorled. Plant forn1 should only be
used if you have a clear example of the fonn such as tree.
Otherwise. use this attribute to validate your identification
base on other characteristics. For illustration purposes. we
will select ..divided" leaves. We now have the woody plants
on South Mountain with divided leaves. If••opposite"is now
chosen (Figure 3 ), you are left with only two plants.
Step Five
Continue to select attributes until the list is sufficiently
narrow. so that it is reasonable to check the images to
validate your identification. In our example, yellow flowers
are present. This choice leaves you with the single plant
-creosote. Congratulations! (Figure 4).
The column ··oistinctives" may narrow the list considerably
at any point in the process, but do not start with this column
since the attributes included are too specific.
Note. this guide does not start with pictures, it ends with them.
It is necessary to first take a closer look at the plant rather
than a static photograph or drawing. This practice will help
you develop an eye for detail and improve your skill when
it comes to identifying the flora of Arizona.
Most of the hikers, bikers, and equestrians enjoying desert
treks in southern Arizona are not trained botanists and most
of the plant guides for the area do a poor job of assisting
them with plant identification that is comprehensive,
accurate, and easy to use. Therefore. our first principle. is
that we have a need .
Secondly, by using the floras completed as master's degree
projects at local universities for the popular recreation sites
in the Sonoran Desert, we achieve a comprehensive list of
plants which a large number of people will encounter as
they seek to enjoy and better understand the wild desert
resource we find in our ••back yard". Therefore, we have a
sound basis to meet the need in principle number one. We
need a better tool to put this inforn1ation into the hands of
interested people.
Since print plant guides are expensive. bulky and incomplete,
it is time to explore an electronic alternative. The ··autofilter"
function in Excel allows you to list a few key. non-technical
attributes and select from that list quite easily to match the
plant in hand with its proper identification. This functionality
is not yet available in palm pilot devices but it is not far
away. In the meantime, a CD can be used in any PC running
Excel. No unique plug-ins or software is needed. In an
age of technology, the time has come to apply this tool
to enhance our outdoor enjoyment. Better understanding
fosters appreciation which leads to better care and a healthier
A link to this site should be available at the Desert Plants
website shortly after the publication date.
Desert Plants
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Desert Plants
The Outstanding Stamens of
Pennisetum clandestinum
Hochst. ex Chiov.
Kathryn Mauz
University of Arizona Herbarium, PO Box
210036, University of Arizona, Tucson, AZ
85721, km_
While walking across the University of Arizona campus in
Spring 2006, I noticed bluish tufts in the lawn of a traffic
island (Figure I). On examination, these tufts comprised
the translucent-whitish stamens of Pennisetum clandestinum
Hochst. ex Chiov. (determined by John Reeder at ARIZ).
The turf grass is native to Africa and widely planted, even
invasive, in other tropical and subtropical regions (Hitchcock
1951; Calderon de Rzedowski & Rzedowski 2001 ). To say
that the stamens were long-exserted is an understatement,
as the filaments - up to 3.6 em long - were several times
the length of the spikelets (Figure 2). Across the apparently
monotypic patch, inflorescences typically bore two spike lets
and, thus, produced a tuft of six stamens (the stamens ofboth
spikelets simultaneously exserted).
Smprisingly, this phenomenon is rarely mentioned in floristic
treatments, and is not part of the original description of the
species published by Chiovenda ( 1903 ). The inflorescence
of Pennisetum clandestinum was described in the Flora
of Tropical Africa as "reduced to a cluster of 2-4 (mostly
3 and rarely I ) spike lets," which may be bisexual or
functionally unisexual. The bisexual spikelet(s) produce
·•very long protruding filaments up to 1 or 2 in long." while
a functionally male spikelet possesses rudimentary stamens
and a functionally female spikelet bears much-reduced
filaments and empty anthers (Stapf & Hubbard 1934: 101 0).
The inflorescence has been depicted with the anthers only
just-protruding from the spikelets (e.g., Chiovenda 1903:
tav. 5-11; Hitchcock 195 I: fig. 1114), or with the stamens
of one spikelet exserted and those of the other not (or not
yet) exserted (e.g., Wipff 2003: 520). In illustrations of
an isolated spikelet, the stamens themselves are typically
shown long-exserted but in a flaccid state (e.g., Hitchcock
1951 : fig. 1114; Wipff 2003: 520 ). Me Vaugh provided an
apt description, invoking the phenomenon observed in the
UA lawn: ··only the narrow tips [of the spikelets] and the
slender stigmas and the upright white filaments 2-3 em long
exserted above the foliage ... the inflorescences (except for
the stamens) are very inconspicuous, and flowering may pass
unnoticed" (McVaugh 1983: 329).
In the 'field' (irrigated lawn) setting, the stamens were
cxscrted only in mid-morning. as they were first collected
on 14 Apr and then photographed on 17 Apr 2006. In the
afternoon and early morning during the same time frame,
the stamens were observed collapsed in disarray, but still
visible on close inspection amid the tangle of stems and
inflorescences in the short-napped lawn. This is the typical
state of the stamens as they are preserved in herbarium
specimens. A specimen has been deposited at the University
ofArizona Herbarium (ARIZ 379989) that includes the plants
at anthesis photographed in Figure 2. (Photos by author)
References Cited
Calderon de Rzedowski. G. & J. Rzedowski. 2001. Flora
fanerogamica del Valle de Mexico, 2nd edition. Comisi6n
Nacional para el Conocimiento y Uso de Ia Biodiversidad,
Chiovenda, E. 1903. [Flora della Colonia Eritrea, parte
prima:] Graminaceae, Cyperaceae, Moringaceae, Papilionaceae, Caesalpiniaceae, Mimosaceae. Annuario del
Reale Istituto Botanico di Roma 8: 21-109.
Hitchcock, A. S. 1951. Manual of the grasses of the United
States, 211<1 edition. revised by A. Chase. U.S.D.A. Miscellaneous Publication no. 200, United States Government
Printing Office. Washington.
Me Vaugh. R. 1983. Gramineae, pp.l-436. In: W.R. Anderson,
ed., Flora Novo-Galiciana, vol. 14. University ofMichigan
Press. Ann Arbor.
Stapt: 0. & C. E. Hubbard. 1934. Gramineae (MaydeaePaniceae)- part 6. pp. 945-1132. In: D. Prain, ed., Flora of
Tropical Africa. vol. 9. L. Reeve & Co., Ltd., Kent.
Wipff, J. K. 2003. Pennisetwn Rich., pp.515-529. In: M. E.
Barkworth. K. :\1. Capels. S. Long, & M. B. Piep, eds.,
Flora of North America. vol. 25- Magnoliophyta:
Commelindae (in part): Poaceae, part 2. Oxford
University Press. New York and Oxford.Figure Captions
Figure I. Ground-level view of the stamens of P.
clandestinum in an irrigated lawn on University of Arizona
campus. 17 Apr 2006. (K. Mauz)
Figure 2. Pressed specimens of P. clandestinum (part of
ARIZ 379989). preserYing the long-exserted, erect stamens
at anthesis. The two spike lets are particularly visible in
the left-hand plant: the t\vo sets of three stamens indicate
the spikelets in the right-hand plant. (K. Mauz)
Figure 1. Bluish tufts in the lawn.
Figure 2. Plants at anthesis.
Desert Plants
Unnatural Landscapes:
Tracking Invasive Species
Ceiridwen Terrill
The University of Arizona Press
ISBN- 13: 978-0-8165-2523-2 (pbk. : alk. paper)
ISBN- 10: 0-8165-2523-4 (pbk. : alk. paper)
220 pp.
Traveling by sea kayak, Ceiridwen Terrill and her husband
Bruce visited several lesser known islands in the southwest
to evaluate the problem of invasive species. In her words,
islands are excellent places for exploring the problem of
invasive species because their native plants and animals are
highly specialized, isolated organisms, often few in number,
and highly susceptible to the negative effects of introduced
species. Invasive species increase rapidly on islands because
their natural predators are not there to keep them in check.
Terrill tours various islands in the southwest and Mexico,
both actual islands and self-containted habitat communities.
Beginning with Nevada's Anaho Island, and continuing
on to Ash Meadows and Death Valley, Midriff Islands in
the Sea of Cortez and Anacapa and Santa Cruz Islands in
California, Terrill takes an in depth look at the damage
resulting from invasive species. Two of the books chapters
are dedicated to plant invaders and two explore the impacts
of invasive animals. All these islands are at different stages
of invasion by exotic species and all are accessible to readers
(although to travel to Anaho one has to volunteer to help
with the bird count).
In the course of this study the author writes that she has
learned "that invasive species haven't just outcompeted
natives for nutrients, space and water. They can also change
fire regimes, alter stream courses, prevent native plants
from regenerating, negatively affect human health and local
economies, and in some cases, become the subject of intense
emotional debate in nearby communities. Terrill claims to
be a journalist but is also a fine biologist and ecologist. She
presents the multifaceted problems of trying to eradicate a
species once it is established. The logistics of eradication is
just part ofthe problem. She describes the actions of Animal
Rights groups thwarting the attempts of ecologists in the
belief that they are doing the right thing.
Terrill discusses that there is often a gray area in invasive
species management. She cites the blue gum eucalyptus
trees planted in the Channel Islands in California in 1850.
The eucalyptus tree harms certain ecological functions but
enhances others. This species provides habitat for monarch
butterflies whose California migration path might have been
eliminated due to human population growth and felling of
native trees. In the case of the eucalyptus the National Park
Service has decided on a compromise. The seedlings are
weeded out and the mature trees are left alone.
Also in the 1850s, white settlers introduced the pig - a
mix of the European wild boar and domestic breeds - for
husbandry and hunting on the Santa Cruz Island. The pig
population exploded, rooting up native plants and destroying
archaeological sites (Chumash Indians). These pigs attracted
the golden eagle to the islands. Once the golden eagles
started hunting on the islands they discovered the island fox.
This small native fox hunted during the daytime and was
much easier prey for the golden eagles than the pigs. Even
though the pigs and the island foxes could co-exist, the pigs
presence caused the decimation of the island fox population
by attracting the golden eagle.
The author maintains that the field of invasion ecology is
still mainly confined to specialists. To overcome the chasm
between scientists, animal rights groups and the general
public there is a need for all to understand what an invasive
species can do to a native ecosystem. The public should know
the ugliness of the process of eradication and the suffering
of the individual animals introduced to a foreign ecosystem.
Terrill's book, with its well researched and well expressed
examples is a good place to begin this understanding.
Plants from the Edge of the World
New Explorations in the Far East
Kew look more appreciatively on the gardens and the
dedication that went into making them.
Mark Flanagan and Tony Kirkham
Timber Press
ISBN 0-88192-676-0
300 pp, approx. 144 color photos
8 b/w photos, 5 color maps
7 x 9", hardcover, $39.95
Mark Flanagan is Keeper of the Gardens in Windsor Great
Park, where he is responsible for the world-renowned Savill
and Valley Gardens as well as the gardens at Frogmore (the
resting place of Queen Victoria and Prince Albert) and Royal
Lodge. He has traveled extensively in search of hardy plants,
with visits to Turkey, eastern Asia, western Canada, and the
western United States. Mark is married and has two children;
they live in a house in the woods in Windsor Great Park.
Plants from the Edge of the World begins on October 13,
1987 with the most violent and destructive storm to be seen
in England for over 250 years. The effects of the storm
on Kew Gardens and Wakehurst Place, Kew's country
garden, were extensive. Kew lost 800 mature trees and
the estimate at Wakehurst Place was over fifteen thousand
trees. Champion trees, scientifically unique trees, and other
historically important trees were among the losses. These
trees had been nurtured by generations ofhorticulturists and
enjoyed by millions of visitors.
Tony Kirkham is Head of the Arboretum and Horticultural
Services at the Royal Botanic Garden, Kew, where he
cares for the existing heritage landscape and woody plant
collections and maintains the integrity and development of
the living scientific plant collections. This latter responsibility
has been the impetus for plant collecting trips to Chile,
South Korea, Taiwan, the Russian Far East, western China
and Japan; many of the trees now growing in the collection
originate from seed collected on these trips. He is married
with two children and lives in London.
Kew Gardens displays a wide geographic spectrum of
temperate trees. In assessing the loss, it started to become
apparent that despite the extensive collections there were gaps
and omissions from several sections of the world, specifically
the extreme edge of eastern Asia. The storm had resulted in
physical gaps in the gardens which could provide space for
new material. Thus from the storm a plant collecting program
was developed which would target areas of the world which
were underrepresented in Kew's collections.
Mark Flanagan and Tony Kirkham set off for South Korea in
1989, Taiwan in 1992, and the Russian Far East and Sakhalin
Island in 1994. Tony alone completed the last leg traveling
to Hokkaido, Japan in 1997. The two plant explorers related
their adventures in the first person present, an effective
method for involving the reader in their exotic and at times
nerve wracking travels. As with all travelers, food and
accommodations were frequent topics. The two were game
to most everything but couldn't quite manage the hae chang
kuk in South Korea - a bowl of eel heads, complete with
the teeth, staring out of a broth of congealed blood and rice.
Their accommodations ranged from adequate to less, once
sleeping in a guest lodge in Taiwan to be awakened by rats
perched at the foot of their sleeping bags! They realized why
their guides had chosen the top bunk beds.
The authors set the scene in the exotic and remote places
they explore, making the reader feel the tension, the cold,
the fatigue but most of all the adventure of the places they
are exploring. The four trips contributed 1223 accessions to
the collections at Kew and Wakehurst Place, comprising 426
different species and varieties. This is a wonderful tale of
botanists' dedication and will make anyone who ever visits
Desert Plants
Preliminary Findings of the
Southwest Monarch Study
C.L. Kline
Boyce Thompson Southwestern Arboretum
37615 E. Hwy 60
Superior, AZ 85273
The Boyce Thompson Arboretum, with the help of a grant
from the Monarch Migration Project West out of Seattle,
Washington, began tagging wild monarch butterflies
(Danaus plexippus) as a part of its Southwest Monarch
Study in September, 2003. The purpose of this research is
to determine the migration behavior of monarch butterflies
in the southwestern United States. Up until2003, very little
attention had been given to the desert southwest in terms of
monarch butterfly activity.
conclusion using similar methods in his book Chasing
Monarchs (Pyle, 1999).
Monarch butterfly research at the Boyce Thompson
Arboretum is focused on three primary questions. First, what
is the destination of migrating monarchs passing through
the southwest? Secondly, which species of milkweeds
(Asclepidaceae) do monarchs use as a larval food plant
while they are in Arizona and the southwest. Thirdly, is
there a "year-round" breeding population of monarchs in
Arizona or are the monarchs witnessed in summer and fall
simply passing through on their way from someplace else
to someplace else? The purpose of this article is to present
preliminary data relating to the first and second questions.
Monarch migration theory has centered around the idea that
the Continental Divide is a natural dividing line between
eastern and western populations of monarchs in the United
States and Canada. The theory has been that monarchs east of
the Continental Divide migrate south while those west of the
Continental Divide migrated south and west to overwintering
sites along the Pacific coast, from northern California south
to Baja, California (Brower, 1995).
The tagging of monarch butterflies, allowing the tracking
of individual butterflies, began in 193 7 with the work of
Dr. Fred Urquhart of the University of Toronto. In January,
1975 Urquhart's research team made the discovery of the
overwintering sites in the Transvolcanic Range located
approximately 200 miles northwest of Mexico City in the
state of Michoacan, Mexico (Urquhart, 197 6).
In 1992, the Monarch Watch organization at the University
of Kansas began tagging monarch butterflies in the eastern
United States. In the western United States, several
individuals and organizations have tagged butterflies at the
overwintering sites in California.
Research conducted at the Arizona- Sonora Desert Museum
(ASDM) from 1998-2001 brought into question the notion
that the Continental Divide formed a natural barrier between
the two populations of monarchs. ASDM's study put forward
the idea that monarchs in Arizona and Sonora, Mexico were
in fact traveling south, rather than west, in opposition to
the accepted migration route of western monarchs (ASDM,
The ASDM data however was based largely on anecdotal
observation of flight bearings rather than the tracking of
individual butterflies. Robert Michael Pyle came to a similar
Figure 1. Asclepias linarea hosting a monarch caterpillar in
Molino Basin near Tucson.
How Do You Tag a Butterfly?
The challenging part of the tagging process is locating areas
where monarchs abound in the late summer and early autumn.
The Southwest Monarch Study begins tagging in August and
continues until the flow of monarchs dries up, typically late
October or early November.
A small fraction of monarchs use Arizona as a travel corridor
when compared to locations in the eastern United States. So,
while tagging fifteen monarchs in a morning for Indiana may
be a subpar day, for Arizona it would be a noteworthy day.
Among the "hot spots" for finding monarchs in late summer
in Arizona are Arivaca Cienega and Sonoita Creek in Santa
Cruz County, and the Canelo Hills, San Pedro River Valley,
and Cave Creek in Cochise County.
Capturing the monarch is no easy feat either. Monarchs tend
to become more active as the day goes on, therefore the best
opportunities for bagging monarchs is usually in the morning.
Successful captures typically require waiting on the monarch to
perch on a twig or flower. After capturing the monarch, remove
it from the net by grasping the butterfly by the leading edge of
the forewings, with the wings held together over the insect's
back. Frequently the barbs on the insect's legs will hook on
the net, but a gentle tug typically dislodges the insect.
Table 1. Number of monarchs tagged since 2003.
The Southwest Monarch Study has tagged over 2000
monarchs since tagging began in 2003 (see Table 1). Many
of these monarchs have been farm-raised insects as a part
of the Monarch Pavilion activities at the Desert Botanical
Garden (DBG) in Phoenix. Each year DBG conducts
education activities relating to monarch butterflies during its
Monarch Pavilion exhibit in October. Among these activities
are programs about the tagging efforts of the Southwest
Monarch Study, which include tagging demonstrations. DBG
has worked diligently to acquire the necessary permits from
state and federal officials to release tagged monarchs.
Figure 2. This tagger is correctly holding the butterfly by
the leading edge of its forewings. The tag is placed on the
middle of the discal cell of the right hindwing. (Adriane
The tags that are used are 5/16"diameter stickers, light blue
in color, each with an individual identification number and
contact email address. The tags are affixed to the discal cell
of the underneath side of the hindwing of the butterfly. Press
down firmly on the tag to be sure that it is securely attached
to the wing. Prior to releasing the insect it is important to
record data. This data includes the tagger's name, tag number,
date, gender of the butterfly, location, and what the butterfly
was doing when it was captured.
Table 2.
Tag# Location
D978 DBG
H826 DBG
H475 DBG
K664 DBG
It is important to note that the 26 percent increase in wild
monarchs tagged between 2005 and 2006 was the result of a
concerted effort to recruit citizen scientists from throughout
Arizona to help with the tagging. Three tagging trainings took
place in southern Arizona during August and September of
2006. Nearly 60 citizen scientists participated in the training
with ten individuals actively pursuing and tagging monarchs
on their own following the training.
Of the 2217 monarchs tagged since the 2003, the study
has acquired recovery information for eight butterflies
(see Table 2). The table indicates one of the problems
frequently encountered with citizen science projects, that
being incomplete data. Recovery data for Monarch H826
was sent via email to the study, including a digital image of
the butterfly. Unfortunately the sender of the email did not
provide any location information.
Trek Bearing
Recovery Location
Michoacan, Mexico
Awhatukee, AZ
Youngton, AZ
Scottsdale, AZ
Michoacan, Mexico
Desert Plant.\'
The monarch recovered in Michoacan. Mexico in 2006
presented its own set of challenges. The finder of this butterfly
was a monarch researcher who had captured the monarch
for butterfly mass studies. Unfortunately the monarch
escaped before tag information could be recorded.
Another interesting piece of data is Monarch 1828. This
butterfly was actually recovered twice. The butterfly was
photographed in Youngtown, Arizona approximately 23 miles
from its release location. Two days later the same butterfly
was spotted again by a homeowner in Tonopah, Arizona 3 7
miles from the previous sighting.
The trek bearings of these few butterflies that have been
recovered indicate that there is no clear pattern of travel of
these butterflies. Monarchs D978 and E472 were recovered
south and southeast oftheir release locations. Monarchs 1828
and H475 were recovered west of their release points while
K664 was recovered northeast of the release point. The short
distance traveled by H475 and K664 could indicate a search
for nectar rather than a migratory heading.
Another aspect of the study is to determine milkweed
preferences of reproductive female monarchs in Arizona.
Currently the Boyce Thompson Arboretum does not have a
captive breeding program for monarchs, therefore milkweed
preferences need to be ascertained from anecdotal evidence
presented by milkweed monitoring citizen scientists.
While this anecdotal evidence can be very subjective based
on the location of monitors, season of monitoring. and
other factors, the anecdotal information has yielded some
food for thought. Southwest Monarch Study milkweed
monitors observed wild populations ofAsclepias asperula. A.
speciosa, A. tuherosa, A. suhulata, and A. subverticillata
throughout the course of the growing season. Of these
species, only A. suhverticillata was ever found to be hosting
monarch caterpillars. In isolated observations, A. linaria and
A. nyctaginffolia were also found to be hosting caterpillars.
As a part of this aspect of the study, an attempt has been
made to propagate as many species of native Arizona
milkweed as possible at the Boyce Thompson Arboretum.
During the course of 2006, eleven Asclepias species were
growing in one and two gallon pots at the Arboretum (see
Table 3).
On two occasions during the summer and fall of2006, fertile
female monarchs visited the "milkweed patch" and laid eggs.
Data was collected regarding which species of Asclepias
were chosen for egg laying by these fertile females. Upon
discovery ofthese larvae and eggs, the individual plant hosts
were covered with a net bag to prevent larvae from traveling
from one plant to another.
Since Arizona milkweeds have various growth forms
including shrubs, sub-shrubs, single-stemmed upright
perennials and others, it was determined to record data as
caterpillars per stem since whole plants could vary greatly
in terms of available forage for a caterpillar.
While the results presented in Table 3 are too minimal
to justify a statement of preference of the these monarch
females, the results do present possible trends to study further.
The two females in question obviously stayed away from
certain Asclepias species including A. subulata, A. albicans,
A.asperula, and A. linaria.
Table 3. Host Preferences by Monarch butterflies
August 21,
1251* II
per stem
December 2,
per stem
The females also appeared to be attracted to A. angustifolia
and A. erosa, even though those species presented a minority
of the total population of Asclepias available to choose
Obviously the results presented here are very preliminary, but
at the same time they propose some interesting ideas. Much
more study is needed regarding monarch migratory behavior
in Arizona and the southwest. Further study is also required
regarding the utilization of southwestern milkweed species
by reproductive monarchs.
While taking a citizen science approach to this research
has certain drawbacks, as mentioned previously, it also
provides unique opportunities not easily garnered with such
a large research area and such a mobile research subject.
The recruitment of capable citizen scientists is every bit as
important to the study as is the acquisition of nets and tags.
Citizen scientists interested in participating in this important
research should contact the author or the Boyce Thompson
Arboretum at 520-689-2723. (All photos by author unless
otherwise indicated.)
Figure 4. Asclepias subverticiliata growing in a wet ditch
near Pine, AZ (Gila County)
Literature Cited
Arizona-Sonora Desert Museum. Migratory Pollinators
Program Table 10. {homepage on the internet}. Tucson,
AZ: [ciged 2006 Mar 13]. Available from: http://www. 0. php
Brower, L.P. 1995. Understanding and misunderstanding the migration of the monarch butterfly (Nympahlidae) in North America: 1857-1995. Journal of the
Lepidopterists'Society 49: 304-385.
Pyle, R.M. 1999. Chasing Monarchs: Migrating with the
Butterflies of Passage. Houghton Mifflin, Boston.
Urquhart, F.A. 1976. Found at Last: the Monarch's Winter
Home. National Geographic 150: 161-173.
Figure 5. Asclepias erosa growing along Alamo Dam Road
in La Paz County, AZ.
Figure 6. Monarch H826, recovery location unknown.
Author unknown.
Desert Plants
Figure 7. A tagging training session near Palominas, AZ.
Figure 8. A young tagger looking eye to eye with a monarch butterfly.
Figure 9. Monarch 1828 was recovered twice on its journey west (Earle Robinson)
Saudi Arabia
Arabian Desert Primer: Ornamental
Potential of Hyper-Arid Adapted Plants
from Saudi Arabia
Jeffrey M. "Pete" Petrie
Director of Studies Canterbury English. S. L.
Madrid, Spain
(Horticultural Specialist. retired
Boyce Thompson Arboretum)
Most adult Americans are familiar with the Arabian Desert
only through the striking landscapes depicted in David Lean ·s
epic film "Lawrence of Arabia:· To a native of the Sonoran
Desert. accustomed to the diverse flora and fauna of what
scarcely seems to be a desert in the classic sense. Saudi Arabia
presents a shocking contrast. Except for the highlands of
the far south along the Yemeni and Omani borders. eastern
Saudi Arabia is truly hyper-arid. Whereas the Sonoran Desert
in most years has a reliable biannual precipitation pattern.
hyper-arid deserts are characterized by periods of at least 1.2
consecutive months without any rainfall whatsoever and no
discernible precipitation pattern.
Saudi Arabia's rainfall is one ofthe world's most variable.
The desert plants have adapted to survive multi-year
droughts which alternate with torrential storms. At Dhahran
in the Eastern Province near the Persian Gulf. during the
five years between a 3 June 1997 storm (75.95 mm) and
a catastrophic flood on 13 December .200.2 (431.8 mm).
o~ly 3 traces of less than a mm of rain fell. I made my two
tnps to Saudi Arabia during the wetter cycle of .2003-5.
during which time a total of four significant rainfalls and
one trace fell (Dhahran Weather). I witnessed the storm of
15 December .2004 ( 103.89 mm) in which the normally dry
lake beds and salt flats (sabkas) quickly filled with flood
waters which stood for weeks.
Desert plants there have not only to contend with this extreme
variability. but also with some of the consistently highest
temperatures on earth. Average maximum temperatures
in June. July and August in Dhahran are typically above
43 ..2 C ( 110 F) while the minimums remain above .29 C (85
F). The July 1998 average maximum was 47.3 C (117 F).
Temperatures in February can spike briefly into the 90's
and during March into the IOO's. However. because of the
proximity to the warm Gult: relative humidity is usually much
higher year round than in the Sonoran Desert. averaging as
high as 90% during the summer months (ibid).
Much of the Arabian Desert is a landscape of sand and rock.
Soils typically lack nitrogen or organic matter and exhibit
little stratification. Strong seasonal north winds known
as shamals can bury plants with sand or strip away the
surrounding soil. Floods can expose their roots. wash them
away or even change the landscape. The impacts of grazing
by sheep. goats and camels and damage by off-road vehicles
cause further harm. One wonders how any plants or animals
can survive here.
The entire native flora of Saudi Arabia's Eastern Province,
an area of 90,000 square miles. amounts to only some 360
species mostly belonging to about 30 families (Mandaville
1968). In the adjacent expanse of the Rub-Al-Khali (the
"Empty Quarter"). which occupies an area larger than
France or Texas. there are only 37 species with one or two
endemics (Mandaville 1990). The area around Dhahran. in
common with most of the Arabian Peninsula, falls within the
extensive Saharo-Sindian floristic region (or Saharo-Arabian
Xeric Scrublands ecoregion). about the size of Alaska and
Montana combined (ibid). (Figure 1.) In general the floristic
diversity is low. but to truly understand the Arabian Desert
one has to see it as a very local patchwork of tenuous and
often tiny microclimates. Differences in conditions within
even a few centimeters can mean the difference between
life and death.
The majority of Arabian species have adapted to the harsh
em·ironment by means of three main survival strategies.
Ephemerals grow quickly during favorable periods, produce
large quantities of drought-resistant seeds, then die. Succulent
perennials have evolved extensive lateral root systems.
water storage cells, thickened epidermis and waxy or hairy
coatings. Most of these plants have reduced or hidden stomata
that open only at night to reduce transpiration. Woody
perennials tend to have reduced leaf surfaces or none at all
and deep root systems to tap hidden water sources. Some
have apparently adapted to benefit from dense cool- season
fogs. (Six fogs occurred during February of2005.) Most plant
growth and reproduction occurs during the winter and brief
spring. Flowers typically open in the early mornings when
pollinators are more active and close by mid-morning when
the temperatures begin to rise.
I first traveled to Dhahran during the fall and winter of
2?0314 (Figure 2.) to visit my wife Beverly Wright. a
kmdergarten teacher at the Aramco compound. Despite the
single heavy rain of the previous December, the surrounding
desert was still recovering from the drought of 1997-2002.
Only the hardiest plants appeared to be thriving. A year later
in December .2004. upon my retirement from the Boyce
Thompson Arboretum. I was delighted to find the desert
transfonned. Ephemerals were everywhere. and previously
leafless or much reduced perennials were growing and even
I focused my preliminary botanical investigations on five
local plant communities. The Rlwnterium steppe (Bundy et
al 1989) is represented among the nearby jebels and wadis.
flat-topped limestone buttes and natural drainages in and
around Dhahran (Figure 3). Weekend trips to the suq-alkhamis (Thursday market) in Hofufl Al-Hasa and Qatif.
the world's largest oases. atTorded opportunities to explore
Desert Plants
Desert Trek
Apr. 13/14, 2006
- - lntematlonalboundary
Figure 1. Map of Saudi and close-up of area around Dhahran.
Figure 2. The author in the sabka from Bronze Age necropolis
Saudi Arabia
Figure 3. Rhanterium steppe, jebels near Dhahran
the oasis plant community (Figure 4). Aramco-sponsored
geology and archaeology excursions allowed us to examine
the sabka (salt flat, Figure 5) and coastal scrub communities
(Figure 6). Joining a four-wheel drive camping club led us
far into the deep dune environment (Figure 7). I found the
jebels and wadis to contain the richest assortment ofbotanical
discoveries, including those which will be examined in detail
at the end of this article. However the dune environment was
perhap the most fascinating and held the most surprises.
Figure 4. AI Rasa date palms and exotic mesquites
The sand dunes which cover approximately one-fourth of
the total area of Saudi Arabia tend to be silicate in origin
(Mandaville 1990) and in the Dhahran area have a distinctly
pinkish cast. The most common woody perennial of the open
sand is Calligonum comosum (Arabic abal; Polygonaceae),
locally preferred as the firewood of choice (Figures 8, 9).
The red fruits are edible and are used by the Bedu as a spice
and as a mouth freshener. The powdered twigs were also
used to tan the insides of leather water bags, and are still
Figure 5. Sabka (salt flat) from Bronze Age necropolis near Bqaiq
Desert Plants
Figure 6. Coastal scrub community at Ras Quarrayah
Figure 7. Every depression is a plant habitat.
Saudi Arabia
sold in twig and powdered form in the Hofuf Thursday
market for medicinal purposes. Traditional uses of the
powder include the treatment of wounds, as a post-partum
wash, flatulence, skin ailments and stomache ulcers (Lebling
& Pepperdine 2006). This and other plants of the shifting
sands are adapted to being periodically buried almost
to the stem tips with no apparent detriment. Other more
opportunistic common plants such as Phoenix dactylifera,
Tamarix arabica, Calotropis procera, Leptadenia
pyrotecnica, Zygophyllum qatarense and the sedge Cyperus
conglomeratus tend to colonize small depressions.
Since my primary interest in plants is horticultural, I made
several visits to the Aramco Nursery to consult with my
colleague Helal Hanai, who had been introduced to me
during a 2003 visit to Arizona by Matt Johnson ofthe Desert
Legume Program. Helal demonstrated to me how the Saudis
had worked out the technique of drip irrigating landscape
plants with highly saline reclaimed water (up to 2,000 ppm)
by watering heavily each night to provide a continual flushing
action. Because of the salinity factor, they have scoured the
globe to find and commercially grow a suitable palette of
heat and salt-tolerant landscape plants, and are continually
testing more (Burton 2001 ). One remarkable discovery from
South Africa was a salt-tolerant clone of Paspalum grass.
The Saudis bought two large shiploads full of stolons in the
early 1980's and began a vast greening project with it (Pers.
comm. 2003).
they have not done to date is fully investigate the ornamental
potential of their own native plants. I noticed that hyper-arid
adapted native plants from the adjacent jebels which had
accidentally seeded into drip-irrigated areas grew riotously
and in many cases bloomed continuously.
I believe some of these plants have landscape potential as
accents and groundcovers in those parts of Arizona and
southern California where drip irrigation with high-salinity
water is a fact of life. Some plants look great throughout
the year once established with no irrigation whatsoever and
may be of benefit in extremely harsh but relatively frostfree sites. The date palm Phoenix dactylifera is a classic
example. Native to Saudi Arabia and adjacent areas, it is
already at home in some of the harshest of deserts throughout
the world (Figure 10). Many native plants were and still are
used ethnobotanically by the Bedu and other more settled
Arabs, while others have proven medicinal potential. Some
are important fodder plants for livestock or provide superior
wildlife value. Here are some of my favorites with notes on
Because of the harshness of the desert, the Saudis have
an inordinate appreciation for and love of lush greenery.
Besides having a long tradition of producing dates, fruits
and vegetables atAl-Hasa and Qatif, they are justly proud of
their gardening prowess with exotic landscape plants. What
Accent plants
Calotropis procera (Ait.)Ait. (Arabic 'ushar, ashkar; English
"apple of Sodom", "giant milkweed"; Asclepiadaceae).
Analgesic, diaphoretic, emetic (Duke 2007). The Bedu
believe this plant to be generally poisonous, since livestock
will not touch it, but sometimes use small amounts of the
latex to fill aching tooth cavities. Twigs are used as chew
sticks and poultices are made from the leaves and applied
to rheumatic joints and wounds (Lebling & Pepperdine
2006). The root bark was used to treat difficult breathing,
pain, paralysis, leprosy, fever including malaria, snake bite
and scorpion stings (Duke 2007). The large spherical fruits
Figures 8. Calligonum comosum in midground
Figure 9. Calligonum comosum, firewood of choice
Desert Plants
give it its common name, and the silky seeds within were
used to stuff pillows. Another historical use was to bum the
wood to obtain a fine charcoal used in the manufacture of
homemade gunpowder (Mandaville 1968). A striking and
unusual shrub with broad, glaucous gray-green leaves and
tight clusters of yellowish blooms, it commonly reaches 2
and rarely 3 meters (Figure 11 ). It is especially adapted to
disturbed and overgrazed sites, growing luxuriantly on the
poorest soils as well as in the deep sands (Figure 12).
12. Calotropis procera on deep dunes
Figure 10. Phoenix dactylifera, date
palm, seedling in sand
Ziziphus nummularia (Aubrev.) (Arabic sidra, nabak; English
')ujube"; Rhamnaceae). Although rarely eaten any more, the
entire ripe fruit and seeds are edible. Historically they were
ground into a powder and eaten raw or cooked with milk or
water (Mandaville 1968). Camel sticks are traditionally made
of the stems (Migahid 1996), wildlife benefit from eating the
fruits and sheep eat the leaves. Studies have demonstrated
significant antibiotic and antifungal activity in the leaves,
stems and roots, as well as the presence of betulin or betulinic
acid, a potential anticancer agent (Maurya 1989). I found a
small isolated grove ofthese lovely small deeply-rooted trees
thriving amidst a dry plain (Figure 13). This is one ofthe few
exuberantly leafy plants which may reduce the number of
leaves during severe drought, but apparently never becomes
truly dormant (Figure 14).
Leptadenia pyrotecnica (Forsskal) Decne. (Arabic markh;
Asclepiadaceae) Diuretic (Duke 2007). The Latin name
comes from the historic use ofthe fluff from the seed pods as
tinder in starting fires. The flowers and fruits are edible, and
are known as ma 'alit (Migahid 1996) (Figure 15). This small
tree owes its marvelous drought-tolerance to its leaflessness
and the fact that the stomata are hidden inside small grooves
on the stems. Looking much like one of the Sonoran Desert
crucifxion thorns, it is at home in some of the driest locations
including the deep sands (Figure 16).
11. Calotropis procera, close-up
Ochradenus baccatus Delile (Arabic qirdi, qurdi;
Resedaceae ). Traditionally used to treat stomach ache
(Duke 2007), and recently discovered to contain important
flavonoids and glycosides, the above-ground parts have been
investigated in the treatment of diabetes (Barakat et al. 1991 ).
This robust yellow-flowering shrub growing to 2 meters tall
by 3 meters wide among the jebels and boulders appears to
Figure 13. Ziziphus nummularia
Figure 15. Leptadenia pyrotechnica green pod
Figure 14. Ziziphus nummularia close-up
Figure 16. Leptadenia pyrotechnica
Desert Plants
be the food plant of choice for migrating birds and nectarfeeding insects (Figure 17). The ripe fruits are sweet and can
be eaten like candy (Figure 18). One large specimen growing
"in the middle of the desert" was observed recently by an
investigator in the Sinai to host thousands of migrants in a
week (Meyran 2007). The plants are gynodioecious and are
one of the few plants in the world that bloom continuously
(Figure 19). This could be due either to large plants
possessing extra-long taproots or to evolutionary selection
for early germination of seeds in the next generation, a
"hedge-bet" against infrequent rains (Wolfe & Burns 2001 ).
In either case, it would be a showy and useful addition to the
landscape in rocky or harsh sites.
Lycium shawii Roem. Et Schult (Arabic 'awsaj, 'awshaj;
Solanaceae). Diuretic, laxative, hepatic, tonic. It was
traditionally used in the treatment of colic, jaundice and to
improve vision (Duke 2007). It is one of the rare desert plants
with fleshy edible fruits (Figure 20), and thus is an important
food and water resource for birds and other wildlife (Izhaki et
al. 2006) (Figure 21 ). The erect rich green foliage and small
cream or blue flowers would provide a showy backdrop,
hedge or accent among boulders.
Figure 18. Ochradenus baccatus pistillate plant close-up
Rhanterium epapposum Linnavuori (Arabic 'arfaj;
Asteraceae) One of the most important grazing plants for
camels, sheep and goats, it is perhaps the signature native
plant of the Dhahran area. It is also the national emblem of
Kuwait. A dense perennial shrub to a half meter tall by one
meter diameter, it has a complicated twig structure (Figure
22) and numerous long-petioled yellow composite flowers
(Figure 23). This deeply-rooted plant copes with extreme
drought by reducing its metabolic activity to a minimum
and becoming as dry as the ambient air, but quickly recovers
when rain falls.
Figure 19. Ochradenus baccatus staminate plant
Figure 17. Ochradenus baccatus staminate plant
Desert Plants
Ground covers
Zygophyllum qatarense M.N.el Hadidi (Arabic harm;
Zygophyllaceae ). A succulent sub shrub of astounding
beauty and versatility, growing in poor soils and sand alike,
this plant provides much of the vegetative cover and is often
found in pure stands in the deep dunes (Figure 24). Despite a
high concentration of salts, it is an important food and water
resource for camels and some wildlife, which learn to eat it
judiciously when other resources fail. Due either to genetic or
environmental factors, reddish or maroon-colored individuals
also occur (Figure 25). A succulent with cream-colored
blooms, it is seemingly unaffected by drought and maintains
a lush appearance year round and even buried to the tips in
sand (Figure 26). Under drip irrigation it shows considerable
promise as a ground cover. (Figure 27).
Figure 24. Zygophyllum qatarense, pure stand
Figure 25. Zygophyllum qatarense, young plant on limestone
Saudi Arabia
Figure 26. Zygophyllum qatarense partly
buried in sand
Fagonia oliverii DC (Arabic sheka'a; Zygophyllaceae).
This is another sub shrub which seems largely unaffected
by drought and is a standout because of its unusual form.
The square twig cross-section and intricate dense zigzag
branching structure, together with the persistent drooping
pyramidal fruits and numerous small bluish flowers combine
to form a striking accent plant (Figure 28). Mass plantings
under drip irrigation could provide an interesting ground
cover display. Although this plant has a wide distribution,
it is little known and there are few references to it in the
Figure 27. Zygophyllum (left) and Heliotropium
as ground covers
Heliotropium bacciferum Forssk. (Arabic ram-ram; English
"heliotrope", "tumsole"; Boraginaceae). Drunk as a tea, it
was historically used as a remedy for sand viper snakebites,
although there is no medical evidence for its efficacy. The
plant boiled in water is still used today as a mouthwash to
cure sore gums and mouth blisters, swellings and ulcers
(Lebling & Pepperdine 2006). It is an important fodder
plant for camels, sheep and goats. A handsome dark green
perennial with small white blooms, it thrives in poorly
drained soils in dry locations. It has a dense and compact
habit, up to a half -meter tall by a meter in diameter, with
a somewhat pungent fragrance (Figure 29). It appears to
thrive nearly as well in the wild as under drip irrigation, but
appears more succulent when watered (Figure 30).
Moltkiopsis ciliata (Forssk.) Johnst. (Arabic halam;
Boraginaceae ). Stiff hairs contribute to the silvery
appearance of the leaves of this lovely perennial at home
even in the harshest sandy sites. Small pink-lavender-bluish
blooms crowded together on numerous scorpioid cymes add
to its elegant appearance (Figure 31 ). There are very few
references to this plant in the literature, and it is as often
listed as Moltkia ciliata. I never observed any drip-irrigated
specimens, but based on its spreading yet erect habit, it
looks like a good candidate for evaluation as a ground
cover (Figure 32).
Figure 28. Fagonia oliverii large plant
Sa/sola baryosma (Schult.) Dandy (Arabic khurrayt;
Chenopodiaceae). Antihelminthic. Used for itches and sores
(Duke 2007). A tough succulent halophyte with a range from
Mauritania in North Africa to the Sind Desert in Pakistan and
beyond which thrives in salty, poorly-drained and heavilycompacted soils. The leaves are arranged like beads on stems
which are often a deep showy red, and the dependable lush
Desert Plants
Figure 29. Heliotropium bacciferum large plant
Figure 30. Heliotropium bacciferum as ground cover
Saudi Arabia
green foliage seems unaffected by drought or summer heat
(Figure 33). Plants which have encroached into drip-irrigated
areas quickly knit together to form a luxuriant ground cover
or border. It may be suitable in large areas with problem soils
in which nothing else will grow. (Figure 34).
Helianthemum lippii (L.) Dum.-Courset (Arabic regroog;
Cistaceae). One of the Arabian Desert natives that is actually
a part of the Mediterranean flora, this plant is perhaps best
known for being an indicator plant for the highly-prized
desert truffle (Tirmania nivea), with which it has a symbiotic
relationship (Iddison 2000). It is apparently grazed by sheep
and goats. An intricately branched, rounded dwarf shrub
with small yellow blooms, it is attractive year round even in
the wild (Figure 35). With a minimum of drip irrigation, it is
capable of doubling its size and has potential as an accent or
ground cover in smaller areas. (Photos by author)
Barakat, H. H., et al. [ 1991] "Flavonoids of Ochradenus baccatus". Phytochemistry. 30:11; pp. 3777-79.
Bundy, G., R. J. Connor, C. J. 0. Harrison. Birds ofthe Eastern
Province of Saudi Arabia. G. Witherby/Saudi Aramco,
London/Dhahran: 1989.
Burton, John J. S. Cultivated Outdoor Plants ofSaudi Aramco.
Saudi Arabian Oil Company, Dhahran: 2001.
Iddison, Phil. [2000] "Desert truffles Tirmania nivea in the
Emirates". Tribulus. 10:1; pp. 20-21.
Lebling, Robert W. and Pepperdine, Donna. Natural Remedies
ofArabia. AI-Turath/Stacey International, Riyadh/London,
Mandaville, James P. Flora of Eastern Saudi Arabia. London: Kegan Paul International Jointly with the National
Commission for Wildlife Conservation and Development,
Riyadh: 1990.
Mandaville, James P. [1968] "Flowers in the sand". Saudi
Aramco World. 19:1; pp. 22-25.
Maurya, S. K., et al. [1989] Content of betulin and betulinic
acid, antitumour agents of Zizyphus species. Fitoterapia.
60: pp. 468-69.
Migahid, Ahmad Mohammad. Flora ofSaudi Arabia. Fourth
Edition. 3 Vols. Riyadh: King Saud University, 1996.
Wolfe, Lome M. & J. L. Bums. [2001] "A rare continuous
flowering strategy and its influence on offspring quality
in a gynodioecious plant". American Journal of Botany.
88: pp. 1419-23.
Figure 31. Moltkiopsis ciliata
Figure 32. Moltkiopsis ciliata as groundcover
Web sites
Dr. James Duke's Phytochemical and Ethnobotanical
Databases: Module 10: Arabic:
http://www.ars-grin. govI duke/syllabus/module 10 .htm
Historical Weather: Dhahran, Saudi Arabia:
Izhaki, Ido, et al.: Fleshy-fruited plants and frugivores in
desert ecosystems:
Meyran, Jonathan: Southern Observations- early spring
http://www. birdingisrael. com/birdN ews/recentSightings/
2007/lightbox/early spring 2007 .html
Desert Plants
Figure 33. Salsola baryosma (khurrayt)
Figure 34. Sa/sola baryosma irrigated
Figure 35. Helianthemum lippii
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