Aridus: bulletin of the Desert Legume Program of the Boyce Thompson Southwestern Arboretum and the University of Arizona

              Volume 16, Number 1

Bulletin of The Desert Legume Program of The Boyce Thompson Southwestern Arboretum and The University of Arizona

April 2004

Elizabeth Davison

Department of Plant Sciences, UA

Director Campus Arboretum

Cassia fistula

Every June my phone starts

ringing. From all over campus, the

questions come. Everyone wants to

know the name of the beautiful tree

with the chains of bright yellow

flowers.

Cassia fistula L. or ‘ golden

shower tree’ is a show stopper when

in bloom. The 30' tall graceful tree

produces yellow 3" flowers that hang

in clusters 12 to 18" in length.

Typically bloom occurs just after leaf

drop in May, so that for several

weeks the naked tree is covered with

long yellow chains, each with a dozen

or more flowers.

Also known as ‘ Indian

laburnum’ or ( in Thailand) ‘ lantern

tree’, Cassia fistula is slender, to 40

feet high, with moderate to fast

growth. On the UA campus, our

specimen grows about 5- 8 ft per

year. A member of the Fabaceae

family, thus related to the spiny, dull

legumes of the southwest deserts,

Cassia fistula is definitely not from

around here. This tree has a relaxed

tropical look, with pinnately-compound

leaves up to a foot in

length, each shiny leaflet 4" long.

The dark brown cylindrical

‘ bean pods’ can be 2 feet long, and

add to the unusual appearance.

Pollination is achieved through bees

which can cover the tree during

bloom. Because the campus lacks a

cross- pollinating donor, pods do not

form on this specimen.

Frost- tender and evergreen,

it is adapted to USDA zones 9.5 and

warmer. However, the tree on UA

campus is thriving in a protected

microclimate with a west-facing

exposure. In Tucson

( zone 9) the leaves renew

each June after the

spectacular bloom. As it

matures, hardiness may

increase. During the winter of

2003- 04, this tree sustained

nearly complete defoliation

on consecutive nights of 19

and 20 degrees F. However,

we are hopeful that stem die

back will be minimal.

Adapted to most

soils, this species appreciates

the heat, but not the drying

winds of the southwest.

Moderate watering in the

summer, along with a shady

root zone, has allowed the

UA ‘ golden shower tree’ to

prosper.

Recently many of the

plants within the large group

of cassias were re- classified

as Senna. This is a botanists’ fine

point, but nonetheless, this species is

still called by Cassia. Native to

India and Malaysia, it has spread

throughout the Pacific tropics.

Several nurseries/ growers in Florida

list it as available. Honolulu’s

“ rainbow shower” tree, familiar to

visitors, is a hybrid between this

species and C. javanica.

Cassia fistula and Delonix regia

Cassia fistula

2 Aridus 16: 1 2003

Known for years as “ purging

cassia”, Cassia fistula is currently

advertised/ marketed as an effective

astringent, purgative/ laxative, and is

used for colic and flatulence. The

active part used in medicine is the fruit

or pods, which are pounded to

release the sweetish pulp.

In the last 10 years, there has

been an increased interest in

biological and medicinal potential of

many members of Fabaceae.

Researchers have evaluated Cassia

fistula for anti- bacterial properties

( wound healing), as a cough

suppressant, and for its potential to

restrict or protect against nematodes.

A recent literature search resulted in

articles testing C. fistula as a

potential marker for evaluating air

pollution levels, as a possible agent to

remove heavy metals from waste

sites, and as a source of potassium in

adult diets.

This striking tree is just one of

dozens of trees introduced to the

University of Arizona campus by

Warren Jones. Warren remembers

bringing seeds from central Mexico

during the 1980’ s. Germination and

culture occurred at the UA

greenhouses at the Campbell Avenue

Farm. Seeds are similar to those of

many other hard- coated legumes;

germination is enhanced if seed coats

are softened or scarified.

The Cassia fistula is a

campus favorite at the University of

Arizona. Its protected site beside the

Nugent building includes both a

warming wall and a shady root zone.

This combination seems to be perfect:

it is thriving on the UA grounds, and

its beauty has earned it the reputation

as the tree that stimulates the most

phone calls in late May and early

June.

Delonix regia

Any one who’s traveled in the

tropics knows this tree. Royal flame

tree, royal poinciana, flamboyant - it

goes by many names. Delonix regia

( Boj. ex Hook.) Raf. is typically seen in

frost- free climates ( USDA Zone 10b).

How could one be living in Tucson

( USDA Zone 9, 2500 ft elevation)?

A member of the Fabaceae,

royal poinciana could be compared to a

red Mexican bird of paradise on steroids!

Beginning in May, it is covered with

bright red flowers, some of them 3- 4"

across. The flowers have the typical

Caesalpinioideae structure, with one

larger petal ( the banner) and 10 stamens.

The upper petal has streaks of yellow

and white, and the stamens are prominent

and curve slightly downward. Flowers

last for several weeks, and the blooming

period in Tucson continues through

August. When covered with its red

flowers, the tree looks like a scarlet

umbrella.

Although Delonix regia is native to

Madagascar, its seeds have traveled

the world, and the species is now quite

common throughout the tropical

climates. It is found lining streets in

some of the world’s most beautiful

places, and most vacationers are familiar

with its beauty. Many people think it is

native to the Caribbean, since a few of

its names ( flamboyant, peacock flower)

originated there. Other people swear

they’ve seen it in the wild in Mexico, or

on mountain sides in Hawaii. Both of

these observations are probably correct.

In the Pacific, one study group

( Pacific Island Ecosystems at Risk –

PIER) is monitoring Delonix regia

occurrence through different islands.

They’ve determined that occasionally it

is somewhat invasive, capable of forming

monotypic stands that exclude other

species. The invasiveness would

naturally depend on climate and other

factors such as ornamental use. Other

authors who’ve noted its mild tendency

to spread say “ who cares – it’s so

beautiful!”

Cassia fistula

Aridus 16: 1 2003 3

loosen and the pods rattle.

The previously- mentioned

greenhouse walkway has been named

“ Magic Alley” since so many tropical

trees, that would otherwise be damaged

by frost, are thriving here. The Campus

Arboretum has participated in the

planning process for the Chemistry

Building Expansion, with the result that

all the trees in “ Magic Alley” will be

protected during the construction

process.

Although royal poinciana can

be propagated vegetatively with tip

cuttings, seed propagation is more

efficient ( and has a better chance of

success). The seeds are speckled, rather

like a fava bean. Typical of most hard-seeded

legumes, germination of royal

poinciana seems to improve with

scarification.

At this time students are

working to germinate and grow out

seedlings of several of the rarer trees on

the University of Arizona campus. The

Desert Legume Program has provided

seeds and greenhouse space. The effort

will increase the number of individuals

that are noteworthy, as well as replace

trees that are not living up to their potential

or that are in jeopardy in some way .

The University of Arizona’s

Delonix regia is just one of hundreds of

species that thrive on the grounds. We

hope it continues to delight us with its

scarlet flowers for years to come.

A little history

During the 1960’ s, 70’ s and

80’ s, the University of Arizona in

Tucson became the “ proving ground”

for dozens of arid tolerant species.

In an effort to evaluate them for use in

urban landscapes, Warren Jones,

Professor Emeritus of Landscape

Architecture installed trees and shrubs

from around the world onto the UA

Campus. The results of his lifelong

dedication are the basis of the book

“ Landscape Plants for Dry Regions”

which he co- authored with Charles

Sacamano ( Fisher Books, 2000.)

Just as importantly, the UA Campus

is now the home of over 400 species

of trees, and at least that many

shrubs, from arid climates on all

continents. The University of Arizona

Campus Arboretum has been

established for the purposes of

preservation, education, and

enhancing this extensive collection.

Please visit our web site at http://

arboretum. arizona. edu

Normally royal poinciana is a

broad spreading tree, 30 to 40 feet high

and much wider than it is tall. However,

the UA’s specimen is taller than it is

wide. Hidden from view most of the

time, it delights students and staff when

the canopy shows its scarlet flowers

above some greenhouses.

Professor Emeritus Warren

Jones had started seeds of several

tropical species in the mid 1970’ s, and

he asked permission to install the trees

into a protected campus site. He was

given a south- facing space near to the

College of Agriculture greenhouses,

where greenhouse irrigation filtered

through the gravel, and steam from the

heaters provided warmth all winter. No

one thought the trees would live very

long. But this site has protected the

famous UA Delonix regia from frost

through its 30 winters.

Two smaller individuals are

suffering in more exposed sites, and one

new seedling may not have survived

2003’ s 19 and 20 degree lows. It is

clear that “ up against a south facing

wall” is the place for tropical trees.

This tree even has elegant leaves.

They are lacy and fernlike, twice-pinnate,

and 12- 20" long. Bright lime

green, they are striking even when the

tree is not in flower. In regions that have

a pronounced dry winter season, the

species is deciduous during the dry

months. In southern Florida, it is partly

so. The UA’s royal poinciana typically

sheds most of its leaves.

With no partner to provide

pollen, the UA tree does not bear fruit.

Two or more trees are necessary for

cross pollination ( and the other trees on

campus have not flowered yet).

Pollinators vary depending on where

the trees grow: bees, small birds, and

other generalist critters. Fertilized

flowers are followed by long dark brown

“ bean pods” – sometimes up to 2 feet

long and 2" wide – hockey sticks hanging

in the trees! When dry, the seeds

Delonix regia

4 Aridus 16: 1 2004

DELEP extends a sincere thank you

to the following individuals and

organizations for their financial

support in 2003.

Ronald E. Abbott

Irma J. Ackey/ Chadland Nursery

Ann R. Alder

Rita Jo Anthony/ Wild Seed, Inc.

Sam Applewhite III

Arid Zone Trees

Arizona Nursery Association

Joan Atwater

Michael N. Baker

R. Mitchel Beauchamp

Jean M. Besich

Emile L. Bourdelier

Dr. Robert and Joan Briggs

Margaret H. Caldwell

Jack and Martha Carter

Andrea Castellanos

Dr. Robert M. Chew

Robin J. Coon

Robin Cuany

Caroline Dierterle

Mary Hope Dillon

Robert M. Dixon

Vernita L. Dombrowski

Frank W. Ellis

Joseph M. Frad

Clark E. Franz

Scott Frische

Leo A. Galloway

LeVerne W. Garcia

Nora E. Graf

Sue Haffner

Billie B. Hardy

Patricia Haydon

Al Hickman

Elizabeth Jo Higgins

William D. Holden

Dr. Charles Hornisher

Drs. Herbert and Mary Hull

Gary and Mary Irish

William A. Kinnison

Dr. William and Patricia Kneebone

Emily R. Johnson

Warren and Carol Jones

Gene Joseph and Jane Evans/

Plants for the Southwest

Dr. Andrew W. Lenssen

Donlon Lobiondo

Marty Maierhauser

Dr. James P. Mandaville

Scott McCleve

Sarah E. McCombs/

Desert Way Gardens, Inc.

Dr. John McDonald

Alice B. McDonnell

Dr. and Mrs. Joseph A. Meeker

Annette Miller

Barbara Miller

Leone L. Mohney

Dorothy Montgomery

Ed and Shari Montgomery

Robert and Mary Neher

Gary Null

John and Dorothy Pasek/

Plantas del Sol

Laura M. Peskin

Virgil S. Priebe and

Donna DiFrancesco

Dr. Tom and Barbara Ramage

Dr. Sol Resnick

Pia Reynolds

Norman C. Roberts

Dr. Alan P. Romspert

James and Lorraine Rorabaugh

Dr. Patrica A. Rorabaugh

Sankyo Co., Ltd.

Drs. John and Helen Schaefer

Cabot Sedgewick

P. R. Sharp

Dan A. Sims

Steven Smiley

Dr. Dale W. Smith

Micheal F. Smith

Richard A. Smith

Dr. Harry W. Springfield

Barbara M. Stockwell

Ted Tawshunsky

Gladys A. Taylor Family

Limited Partnership

Douglas O. Thieme

Dr. Raymond and Jean Turner

James Richard Tyrer

Dr. Robert and Sallaine Upchurch

J. Giles Waines

Wallace Research Foundation

Les Wallach/ Line and Space

Steven D. Watkins

Laurel Woodley

Dr. George A. Yatskievych

Dr. Irving and Margaret Young

Delonix regia

Staff and Volunteers in Action

Aridus 16: 1 2004 5

The Desert Legume Program

Advisory Board membership

personifies a spirit of professional

work experience and strong

advocacy for our work. Issues

relevant to DELEP’s progress were

discussed at the February 6, 2004

Advisory Board Meeting. Since the

program’s earliest days volunteers

have been prime movers in

establishing our seedbank, plant

propagation, and care for our living

collection of plants. They have

provided greenhouse experience, field

tools and labor, plus volumes of

literature for our library. Since its first

meeting on January 27, 1995 our

advisory board has allowed a

different manner of volunteering to

positively effect the Desert Legume

Program. We thank current and past

board members for their spirited

interest and commitment in working

with us, toward the achievement of

program goals.

As individuals, the Desert

Legume Program volunteers come

from a spectrum of dynamic

professional lives. Their works range

from farmers to nurses, engineers,

lawyers, authors, teachers, and

government professionals.

Collectively they are a synergistic

think- tank, which offer suggestions for

use in our daily operations. The local

group has always been one of the

most important advocates of our

work.. Volunteers have come to us

from local and domestic groups, and

several have international work

experience. They have been financial

supporters of DELEP, since it’s

inception in 1988. Your support for

our work and endowments, as

evidenced by your response to our

twice- yearly appeal letters, is greatly

appreciated and is a significant part of

our operating budget, today. We

thank you, too, for being a part of

DELEP.

Matt Johnson spent the first

few days of March at our Yuma

fields. He reports that the continued

removal of the lowest tree limbs in

those fields has allowed the farm staff

there to begin using mechanical weed

control. We thank them for their

work. The relatively cool, wet, and

windless days during his visit allowed

Matt to use our weed- burning tool to

eliminate small remaining weedy

areas. Those conditions permit a

near- perfect environment for

DELEP’s weed control efforts,

including the use of contact

herbicides. The propane burner

allows safe effective removal of

weeds under tree canopies that

cannot be easily removed with

machinery. Weeds within a short

radius of plants are manually

removed. Those fields have now

been thriving for thirteen years, and

weeds have become less problematic

as the large plants shade the

unplanted field areas. Woody

“ volunteers” and woody- stemmed

weeds, after being cut to ground level,

are also nicely controlled using the

burner. Matt collected seed pods

from a few of the species during the

trip. Several dozen specimens there

have been productive over the past 6

to 8 years.

Our condolences to Yuma

volunteer Gail Culver on the passing

of her husband, John Payne, this past

January. Gail and John have been

hardworking volunteers for DELEP

since December of 2000.

The winter in Tucson was

cool with some needed rain, and by

mid- March the days were mostly

reaching into the 80s. During the

middle of the month, Adam and I

transported all of the plants from the

greenhouse to the shade houses.

Before too long, many of the plants

that we grew for Boyce Thompson

Arboretum and the Wallace Desert

Gardens will be transported to those

respective locations. A few more

specimens for our West Campus field

will be planted there, this year. Our

largest nursery specimens are the

trees for the University of Arizona

Campus Arboretum plantings. We

have cared for several Acacia

xanthophloea (“ Fever trees”),

Pithecellobium dulce (“ Manila

tamarind”), Acacia sieberiana,

Dombeya rotundifolia, Acacia

crassifolia, and Erythrina spp. for

the Campus Arboretum during the

past year.

During the past few months,

volunteers Karl May and Wayne

Thank You, Desert Legume Program Advisory Board!

6 Aridus 16: 1 2004

Delep Personnel

William R. Feldman, Ph. D.

Director

Matthew B. Johnson

Botanical Specialist

Ken Coppola

Horticulturist

Margaret Norem, Ph. D.

Editor Aridus

Gina Vance

Administrative Assistant

Volunteer Coordinators

Glenn Branham

Pamela Honaker

Yuma Fields

Dan Sims

Greenhouses

Advisory Board

Rita Jo Anthony

Elizabeth Davison

Stephanie Greene, Ph. D.

Leslie Gunatilaka, Ph. D.

Ryan Huxtable, Ph. D.

Ken Morrow

Suzanne Nelson, Ph. D.

Kathleen C. Rice

Ursula Schuch, Ph. D.

Note publication schedule change:

We regret to inform our readers that

due to funding constraints, Aridus

will be published three times a year

rather than four.

MacGowan have given us a nice

weekend break. They have both

cheerfully cared for our greenhouse

plants, over the weekends. Now our

nursery collection has moved

outdoors, and both Karl and Wayne

have indicated their willingness to help

us by working on Saturdays through

the summer months. Thanks, guys!

Volunteer sessions take a

summer break, from June to August

each year. I expect to call on

volunteers at least once this summer

for a regular seed- cleaning session.

New seedpod collections continue

through the summer, creating a

situation where it becomes hard to

keep up with the amount of seed

processing required when the sessions

resume in autumn. Another idea I

have is to organize a volunteer week

during the summer, when you can

stop in on any day that is convenient,

to help with a wider variety of

projects. Feedback from our local

volunteers will be appreciated. The

two remaining spring volunteer

sessions will be on April 14th and

May 12th.

Faidherbia albida in Yuma field ( MBJ)

Opportunities for Participation

DELEP’s bulletin Aridus, is published

three times annually to stimulate

interest in desert legumes, to inform

our readers of DELEP’s activities,

and to encourage support for

DELEP’s programs. Manuscripts

related to legumes are welcome and

should be mailed to the editor for

review. Subscriptions are complimen-tary

and are available by contacting

the DELEP office. Aridus is published

quarterly by The University of Arizona

on behalf of The Desert Legume

Program.

Tree

Logo

Here

Financial support for DELEP comes

from contracts, grants and contribu-tions

from private industries, gov-ernment

agencies and individuals.

Dedicated volunteer labor is an

integral component of DELEP. Our

volunteers come from many back-grounds

and work on a variety of

projects including wild seed collect-ing,

seed processing, organization

of special events, and office work.

Aridus 15: 1 2004 7

To Contribute: Send a check, pay-able

to U of A Foundation/ DELEP, or

call the DELEP Office concerning a

pledge, a restricted gift, or estate

planning.

Desert Legume Program

2120 E. Allen Road

Tucson, Arizona 85719

To Volunteer:

Telephone our offices

( 520) 318- 7047) or email

kcoppola@ ag. arizona. edu.

Adam Ryan moving the nursery collection. ( KC)

The University of Arizona

Desert Legume Program

2120 East Allen Road

Tucson, Arizona, 85719

U. S. A.

Return Service Requested

NON- PROFIT

ORGANIZATION

U. S. POSTAGE PAID

PERMIT NO. 190

TUCSON, ARIZONA

8 Aridus 16: 1 2004

Haematoxylum brasiletto trunk, Yuma, Arizona ( MBJ)