Key to southwestern trees

Historic, Archive Document

Do not assume content reflects current
scientific knowledge, policies, or practices.

Southwestern

Vrees

US.DEPT. OF AGR!
FOREST SERVICE

SOUTHWESTERN
FOREST & RANGE
EXPERIMENT
STATION

Raymond Price, Director

c Research Jleport 7Vo.8
September 1951

KEY TO SOUTHWESTERN TREES

By Elbert L. Little, Jr,,

Forester

(Dendrology

This key to the native trees of New Mexico and Arizona (132 spe-
cies with 3 additional naturalized species) is a supplement to the non-
technical illustrated handbook. Southwestern Trees, 27 Its primary purpose
is to provide foresters, botanists, students, and others with a precise,
ready, nontechnical means of identifying trees and tree specimens through-
out the year, including seasons when flowers and leaves are lacking.
However, many native trees can be named easily by reference to the draw-
ings, descriptions, distribution notes, and common names in the handbook.

Identification by Families

Often you can recognize the plant family to which a specimen be-
longs, These plant families are listed in the usual botanical order
in Southwestern Trees under Contents (page ii), The List of Species of
Southwestern Trees on pages 25 to 28 of this key groups the 135 species
into 60 genera and 32 plant families. Fourteen of these families have
only 1 tree species each, however.

Most southwestern tree species are grouped within relatively few
large families, the 5 largest containing 75 species. The pine family
(Pinaceae, page 10), first and largest with 18 tree species, contains
the conifers or softwoods (gymno sperms) with needlelike or scalelike
evergreen leaves and seeds borne exposed in a cone: pine, pinyon, spruce,

Douglas-fir, fir, cypress, and juniper. The willow family (Salicaceae,
page 31) > well represented in moist soils along streams, has 17 tree
species: 4 of cottonwood, quaking aspen, and 12 of tree willow. Members
of this family bear male and female flowers on different trees in early
spring in long narrow clusters (catkins) and have seed capsules with many
cottony seeds. The 12 tree species of oakP comprising the beech family
(Fagaccae, page 46) , are recognized by the acorn fruit with cup at base
and by the winter buds 3 or mere in a cluster at tip of twig. Another
large family, the rose family (Rosaceae, page 55) •> is represented by 13
tree species with roselike flowers, including vauquelinia, serviceberry,
hawthorn, cliffrosc, mount a in -mahogany, cherry, chokecherry, and plum.

The legume family (Legtaminosae, page 63) has 15 tree species character-
ized by beanlike pods and seeds: lysiloma, acacia, mosquito, screwboan,

redbud, Jerusalcm-thorn, paloverde, mescaibean, kidneywood, smokethorn,
locust, tesota, and coralbean.

"“'Division of Dendrology and Range Forage Investigations, Forest
Service, Washington 25, D, G. Formerly associate forest ecologist,
Southwestern Forest and Range Experiment Station,

—'Little, Elbert L«, Jr. Southwestern trees, a guide to the
native species of New Mexico and Arizona, U. S, Department of Agricul-
ture, Agriculture Handbook No, 109 pp«, illus, 1950. For sale by
Superintendent of Documents, U. S. Government Printing Office, Washing-
ton 25, D, C, Price 30 cents.

- 1 -

Throe more families contain 19 additional tree species » The lily
family (Liliaceae, page 26) has 5 tree species of yucca and 1 of nolina,
small trees with stout trunk unbranched or with few stout branches and
with grasslike or bayonetlike evergreen leaves. Seven species of tree
cacti, with swollen succulent green branches and numerous clusters of
radiating spines, such as saguaro, organpipe cactus, senita, and cholla,
are in the cactus family (Cactaceae, page 88), The olive family (-Olea-
ceae, page 93), with 5 tree species of ash and 1 of forestiera, is charac-
terized by paired (opposite) leaves.

How to Use This Key

The key is especially useful for distinguishing closely related
species in large groups, such as oaks and willows, and for naming speci-
mens of various small' -leaved species with superficial resemblance and
specimens of small, unfamiliar families. A key is an outline or short
cut for identifying a specimen by elimination, the species being arranged
into two groups according to one or more pairs of contrasting characters
and each group subdivided successively into two until only the single
species fitting the specimen remains. Paired groups in this key are
designated by the some letter, single and double, beginning with "A" and
"AA," at the left of the page and are equally indented by steps. Follow
the key step by step under the group agreeing with tho specimen until
you reach the name with page number in the handbook. Then compare the
drawing, description, and range as a check. If a species is not found
in both New Mexico and Arizona, this fact is mentioned in the key as a
further aid.

In this nontechnical key, simple descriptive terms have been sub-
stituted for botanical terminology with only -slight loss of technical
accuracy. Readily distinguishable leaf, twig, spine, and bud characters,
are used, with supplementary references to fruits when those remain
attached or arc important. As flowers arc not mentioned, trees or
specimens can be identified at any season. Technical keys based upon
natural botanical relationships best shown by flower and fruit characters
are available in published floras of Nov? Mexico and Arizona,

As mentioned in the key, leaves usually are single (alternate) or
paired (opposite) or sometimes crowded together at a place (node) on a
twig* After leaves arc shed, their leaf scars and winter buds just
above mark the nodes and loaf arrangement. The key distinguishes leaves
as simple (with a single blade) and compound (divided into leaflets).
Leaflets usually arc smaller than leaves and are attached on a common
leafstalk that sheds with them. Also, the leaf has a developing bud at
its base, while the leaflets of a compound leaf do not. In nine south-
western tree species of the legume familjr the leaves are twice compound
(bipinnatcly compound), that is, with tho leafstalk or axis branched
into divisions on each side. Southwestern Trees illustrates for each
species (except conifers or gymnosperms) a single leaf, showing whether
it is simple or compound.

Suggestions from users of this key about any parts which may not
be satisfactory, as well as improvements, will be gratefully appreciated,

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The Fivo Parts of This Key

Bogin identifying specimens directly with one of the following
five parts of this key, according to the descriptions and notes at the
head of each part:

Part 1, Key to Conifers or Softwoods (Gymnosperms) , page 4*

Part 2, Key to Yuccas, Nolinas, and Palms (Monocotyledons), page 6.
Part 3, Key to Spiny Hardwoods (Dicotyledons), page 7«

Part k3 Key to Spineless Hardwoods (Dicotyledons), page 11,

Part 5j Winter Key to Deciduous Soinelcss Hardwoods (Dicotyledons),
page 20,

Since most species of southwestern trees arc evergreen or spiny,
you can use Parts 1 to 4 throughout the year. However, use the extra,
winter key, Part 5* instead of Part 4 for spineless trees in seasons
when the foliage is shed. If in doubt about which part to use, first
try the following summary key to the five parts:

A. Trees resinous, usually with straight trunk and single axis; leaves
necdleliko or scalclikc, mostly not spine-tipped, evergreen; seeds
borne exposed on scales of a cone (berrylike and enclosing seeds in
juniper); trunk with bark and wood distinct and with annual rings in
wood — -Part 1, Key to Conifers or Softwoods (Gymnosperms), page 4#

AA. Trees mostly nonresinous, with branched or straight trunk; leaves
of various shapes, commonly flat and broad, deciduous or evergreen
(if scalolike, not evergreen) or none; seeds produced from a flower
and enclosed in a dry or fleshy fruit — Flowering Plants (Anglos perms) ,
B, Trees with stout trunk unbranched or with few very stout branches,
bearing at end a cluster of many long, spine-tipped or spiny (ex-
cept nolina), grassliko or bayonctlikc- (or fanlike), parallel-
veined, evergreen leaves; dead leaves remaining attached against
trunk and branches; trunk with woody portions irregularly dis-
tributed, without clear distinction of bark and wood and without
annual rings— Part 2, Key to Yuccas, Nolinas, and Palms (Mono-
cotyledons), page 6,

BB. Trees usually with many branches and slender twigs (or few swollen
green branches in cacti) bearing net-veined leaves, (or scalclikc
or none) variously arranged, deciduous or evergreen but shedding
promptly upon death; trunk with bark and wood usually distinct
and with annual rings in wood — -Hardwoods (Dicotyledons),

G, Trees spiny, with branches or twigs bearing spines or ending
in sharp points or with spiny-toothed evergreen leaves; leaves
deciduous or scalclikc or none or spiny-toothed evergreen
(except tesota) — Part 3> Key to Spiny Hardwoods (Dicotyledons),
page 7.

CG. Trees without spines on branches, twigs, or leaves; leaves
deciduous or evergreen, mostly broad and flat.

D. Leaves present— Part 4? Key to Spineless Hardwoods (Dicoty-
ledons), page 11,

DD. Leaves absent (shed)— Fart 5, Winter Key to Deciduous
Spineless Hardwoods (Dicotyledons), page 20,

- 3 -

PART 1, KEY TO CONIFERS OR SOFTWOODS (GYMNOSFERtS)

Trees resinous, mostly with straight trunk and single axis 5
leaves necdlelikc or sealelike, mostly not spine-tipped, evergreen;
seeds borne exposed on scales of a cone (berrylike and enclosing seeds
in juniper),

A, Leaves necdlelikc, more than 5/8 inch long,

B, Needles in bundles of 2 to 5 or sometimes single, with a sheath
at base (at least when young) — PINE, PINYON (Finns) .

C, Needles less than 4 inches long,

D, Needles 2 or 3 in bundle or single,

E. Needles 1 to 2 inches long,

F, Needles 3 in bundle, slender, dark blue green — •MEXICAN
PINYON (Pinus ccmbroides Zucc.), page 10,

FF, Needles 2 in bundle or single, mostly stout.

G. Needles 2 in bundle (single and slender in a form
in central Arizona), yellow green — PINYON (Pinus
edulis Engclm.), page 11,

GG, Needles single, stout and stiff, gray green;
northwestern Arizona and not in New Mexico—
SINGLELEAF PINYON (Pinus monophylla Torr. & Freni, ),
page 12,

EE, Needles 2^ to 4^ inches long, 3 in bundle — CHIHUAHUA PINE
(Pinus loiophylla Schicdc & Deppe var, chihuahuana
(Engclm.) Shaw), page 14.

DD. Needles 5 in bundle.

H. Needles less than 2 inches long, dark green, numerous,
densely crowded and pressed against twigs — BRISTLECONE
PINE (Pinus aristata Engclm.), page 13,

HH. Needles more than 2 inches long, blue green, spreading
and not crowded on twigs — LIMBER PINE (Pinus ficxilis
Jam.es), page 13 .

CC. Needles more than 4 inches long,

I. Needles 4 to 7 inches long — PONDEROSA PINE (Pinus ponderosa
Laws.), page 15.

II. Needles 8 to 12 inches or more in length — APACHE PINE
(Pinus latifolia Sarg.), page 16.

BB. Needles single, without a sheath at base,

J. Needles 4-angled, ' sharp-pointed; older twigs roughened by peg-
like bases of fallen needles — SPRUCE (Picca).

K. Twigs and loaf bases mostly hairy; needles not stiff, dark
or pale blue green; cones about 2 inches long — ENGELILANN
SPRUCE (Picca engclmanni Parry), page 17.

KK. Twigs and leaf bases mostly not hairy; needles stiff and
spine-pointed, dull blue green or silvery blue or darker
on older parts; cones mostly more than 3 inches long —

BLUE SPRUCE (Picca pungens Engclm.), page 17*

JJ, Needles flat, blunt or pointed; older twigs not rough.

- 4 -

L. Needles with short, narrowed leafstalks; cones hanging down,
with 3-pointed bracts — DOUGLAS-FIR (Pseudotsuga taxifolia
(Poir.) Britton), page 18,

LL. Needles without leafstalks; cone upright, in top of tree —

FIR (/lies) .

M, Needles of lower branches lg to 2g inches long, pale

blue green or silvery; twigs hairless or sometimes hairy;
cones mostly grayish green — WHITE FIR (Abies cone ol or
(Gord. & Glend.) Hoopes), page 19.

MM. Needles of lower branches 1 to 1-3/4 inches long, dark
blue green; twigs hairy; cones dark purple — ALPINE FIR
(Abies lasiocarpa (Hook.) Nutt.), page 20.

AA. Leaves scalelike, crowded and closely overlapping, less than 1/8
inch long, or on leading twigs needlelike, up to ^ inch long,

N. Leafy twigs regularly and thickly branched almost at right angles;

seeds in hard, dry, rounded cones which remain attached — ARIZONA
CYPRESS (Cupressus arizonica Greene), page 20,

NN. Leafy twigs irregularly branched at small angles; seeds in a mealy
or juicy "berry". — JUNIPER (Juniperus).

0. Leafy twigs relatively slender, the younger twigs about l/32
inch in diameter and often drooping; scale leaves grajr green

or blue green; older twigs becoming smoothish and reddish brown

or dark red.

P. Scale leaves mostly with a whitish resin dot or gland; bark
deeply furrowed into checkered or square plates; "berry"

g inch in diameter, mealy, 3- or 4-scedod — ALLIGATOR JUNIPER
(Juniperus deppeana Steud.), page 22.

PP. Scale loaves without resin dot; bark fibrous and shreddy;
"berry" ^ inch in diamoter, juicy, mostly 2-seeded — ROCKY
MOUNTAIN JUNIFER (Juniperus scopulorun Sarg.), page 22.

00. Leafy twigs relatively stout and stiff, younger twigs almost
l/l6 inch in diameter; scale leaves 3^-ellow green; older twigs
scaly or shreddy, gray or brown; bark fibrous and shreddy.

Q. Plant usually a spreading shrub with several curved branches
from ground and usually without a single upright trunk;
leafy twigs bunched and crowded at ends of branches; pollen
and seeds borne on different trees (dioecious); "berry" ^
inch in diameter, juicy, 1-seeded — ONE-SEED JUNIPER
(Juniperus monosperma (Engelm, ) Sarg,), page 23.

QQ. Plant usually a tree with definite upright trunk, branching
usually several feet above ground; leafy twigs not con-
spicuously crowded at ends of branches; pollen and seeds
borne on same tree (monoecious); "berry" ^ to 5/8 inch in
diameter, mealy, 1- or 2-seed — UTAH JUNIPER (Juniperus
osteosperna (Torr.) Little), page 24*

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PART 2, KEY TO YUCCAS, MOLINAS, AND PALMS (MONOCOTYLEDONS)

Trees with stout trunk unbranchcd or with few very stout branches,
bearing at end a cluster of many long, spine-tipped or spiny (except
nolina), grasslike or bayonctlikc (or fanlike), parallel-veined, evergreen
leaves $ dead leaves remaining attached against trunk and branches ; trunk
with woody portions irregularly distributed, without clear distinction
of bark and wood and without annual rings,

a. Loaves broad and fanlike, with long spiny leafstalk; rare in Kofa
Mountains, Arizona, and not in New Mexico— CALIFORNIA WASHING-TONIA
(Washingtonia filifora (Linden) H. Wendl.), page 24*.
aa. Leaves narrow, grasslike or bayonctlikc, without leafstalk,

b. Leaves ending in a sharp spine — -YUCCA (Yucca) ,

c. Leaves flat and flexible.

d. Leaf edges bearing many minute sharp teeth; trunk with many
widely spreading branches; not in New Mexico — JOS HU A -TREE
(Yucca brevifolia Eng elm, ) , page 27*

dd. Leaf edges without teeth; trunk unbranched or with few
branches,

e. Leaves less than \ inch wide, with threads along edges —
SOAPTREE YUCCA (Yucca data Engelm,), page 26*

oc<* Leaves more than l' inch wide, without threads along

edges — SCHOTTS YUCCA (Yucca schottii Engolm.), page 28*
cc. Leaves concave and stiff,

f. Leaves 3/4 to l| inches wide; trunk mostly with few
branches; not in New Mexico — -MOHAVE YUCCA (Yucca mohavensis
Sarg,), page 29.

ff. Leaves 1/ to 2 inches wide; trunk mostly unbranchcd; not in
Arizona — TORREY YUCCA (Yucca torreyi Shafer), page 30.
bb. Leaves not ending in a spine; not in New Mexico — BIGELOW NOLINA
(Nolina bigclovii (Torr.) S. Wats.), page 30*

- 6 ~

PART 3, KEY TO SPINY HARDWOODS (DICOTYLEDONS)

Trees spiny, with branches or twigs bearing spines or ending in
sharp points or with spiny-toothed leaves; leaves deciduous or scalclike
or none or spiny-toothed evergreen (except tesota).

A. Branches swollen, green, covered with numerous clusters of sharp,
radiating spines and containing soft, watery tissue — CACTUS FAMILY
(Cactaceao) .

B. Branches more than 4 inches in diameter, not jointed, composed of
longitudinal ridges and grooves — CEREUS (Ccreus) .

C. Trunk single, massive, more than 1 foot in diameter, becoming
branched above; not in New Mexico — SAGUARO (Corpus gigantous
Engclm. ), page 88,

CC. Trunk absent but many (10-50) branches from ground 4 to 8
inches in diameter, usually unbranchcd above,

D, Branches cylindrical, with 12 to 19 longitudinal ridges;

not in New Mexico — ORGANPIPE CACTUS (Ccreus thurberi Engclm. ),
page 90.

DD, Branches angular, with usually 5 to 7 longitudinal ridges;
not in New Mexico — SENITA (Ccreus schottii Engelm. ), page 91.

BB. Branches less than 2 inches in diameter, jointed, composed of many
tubercles — CHOLLA (Opuntia) .

E. Joints of branches more than l£ inches in diameter, pale green,
with rounded tubercles less than twice as long as wide; spines
covered with straw-colored sheaths; fruits spineless, prolifer-
ating and hanging in branching clusters; not in New Mexico —
JUMPING CHOLLA (Opuntia fulgida Engelm.), page 92.

EE. Joints of branches less than 1^ inches in diameter, with

tubercles more than twice as long as wide; sheaths of spines
mostly shedding the first year; fruits single or sometimes 2
or 3 in a chain,

F. Tubercles of joints less than 3/4 inch long; fruits mostly
not spiny, fleshy when mature, remaining attached through
the winter,

G. Joints of branches green, mostly more than 1 inch in
diameter; fruits bright yellow, strongly tuberclcd —

TASAJO (Opuntia spinosior (Engelm.) Tourney), page 93*

GG. Joints of branches purplish green or dark green, loss
than 1 inch in diameter; fruits green tinged with purple
or red, not strongly tuberclcd; not in New Mexico —

STAGHORN CHOLLA (Opuntia versicolor Engelm.), page 94.

FF. Tubercles of joints long and narrow, 1 to 2 inches long;

fruits spiny, dry, not remaining attached; not in New Mexico—
BUCKHORN CHOLLA (Opuntia acanthocarpa Engclm. & Bigcl.),
page 94.

- 7 ~

AA. Branches and twigs not swollen, hard, with relatively fewer single
or paired spines. -t>r with spiny-toothed evergreen leaves,

H, Twigs not spiny; leaves spiny-toothed and evergreen,

I, Leaves oval to nearly round, flat, edges with many spiny teeth;
fruit a red berry; not in New Mexico — KOLLYLEAF BUCKTHORN
(Rhamnus crocca Nutt, var. ilicifolia (Kellogg) Greene),
oage 8 4.

H. Lc aves variously shaped, if oval to nearly round then not
flat; fruit an acorn — OAK (Qucrcus),

J, Veins slightly sunken on upper surface and prominently
raised on lower surface — NETLEAF OAK (Quercus reticulata
Humb, & Bonpl.), page 46,

JJ , Veins not sunken on upper surface and only slightly raised
on lower surface.

K. Leaves with few spiny teeth, flat, shiny yellow green on
both sides — EMORY OAK (Qucrcus omoryi Torr.), page 52.

KK, Leaves with many spiny teeth, mostly curved or crisp and
not flat,

L, Leaves blue green above, yellowish green beneath,

mostly less than 1 inch long — SHRU3 LIVE OAK (Qucrcus
turbine 11a Greene), page 48.

LL, Leaves shiny yellow green above, yellowish or whitish
beneath, mostly more than 1 inch long — PALMER OAK
(Qucrcus chrysolepis Liebn. var. palmer i (Engclm, )

Sarg. ), page 51.

HH. Twigs bearing spines or ending in spines; loaves neither spiny
(except southwestern coralbcan) nor evergreen (except tesota).

M, Spines formed by sharp ends of ordinary twigs (in a few species
additional single spines at some loaf bases or nodes); leaves
simple or scalclikc or none (twice compound in yellow pal overdo).

N. Twigs green, leafless most of year,

0, Twigs with minute longitudinal whitish lines, hairless,
flexible, upright, rushlike, in broomlike masses; fruit
a long-pointed capsule 3/4 inch long; not in New Mexico —
CANOTIA (Canotia holacantha Torr.), page 79*

00. Twigs without longitudinal lines, finely hairy when
young, stiff, spreading,

P. Twigs gray green, covered with pressed silky hairs,
commonly branching at small angles; clusters of old
fruits with a ring of 5 to 10 dry segments £ inch
long remaining attached; not in Net; Mexico—

HOLACANTHA (Holacantha emoryi A. Gray), page 74.

PP. Twigs dark green or yellow green, hairless except when
young, branching at wide angles.

Q. Twigs mostly dark green; leaves scalclikc, soon
shedding; fruit a black berry less than 5 inch in
diameter — ALLTHORN (Kocbcrlinia spinosa Zucc.),
page 88. ~ " “

QQ. Twigs, branches and bark 3/cllow green; leaves twice
(bipinnately) compound, iiith leaflets l/8 inch or
less in length, soon shedding; fruit a pod 2 to 3
inches long; not in New Mexico — YELLOW PALOVERDE
(Ccrcidium microphyllum (Tori;) Rose 4 Johnst.),
page' 68.

- 8 -

Nil. Tvdgs gray or brown; loaves present or shed, (very short-lived
in smokethorn).

R. Spines few at ends of some short lateral twigs (or absent)
twigs reddish brown or gray with scattered whitish dots
(lcnticcls); leaves more than 2 inches long, with veins
raised beneath; not native in Arizona — AMERICAN PLUM
(Prunus amcricana Marsh.), page 62,

RR. Spines many, at ends of most twigs; twigs not as above;
leaves less than l|- inches long, with inconspicuous veins.

S. Twigs gray or silvery with dense pressed hairs and with
brown gland dots; leafless most of yean; not in Now
Mexico — SMOKETHORN (Dalca spinosa A, Gray), page 71.

SS. Twigs short hairy or hairless, neither silvery nor with
brown gland dots,

T. Twigs mostly brown; leaves more than 3/4 inch long —
GUM BUMELIA (Bumclie lanuginosa (Michx. ) Pers. var.
rigida A. Gray), page 97.

TT. Twigs light gray, leaves less than 3/4 inch long —
CONDALIA (Condalia).

U. Leaves 3/8 to 3/4 inch long, not narrowed toward
base; berrylike fruits more than ^ inch in
diameter, blue black, sweet— LOTEWOOD CONDALIA
(Condalia obtusifolia (Hook.) Weborb.), page S3,
UU. Leaves \ to inch long, narrowed toward base;
berrylike fruits less than ^ inch in diameter,
black, very bitter; not in New Mexico — BITTER
CONDALIA (Condalia globosa Johnst.), page 83*

MM, Spines scattered along twigs or at leaf bases (nodes) but not
at ends of twigs; leaves simple or compound, not scalclikc.

V. Twigs reddish brown, with scattered sharp spines 3/4 to 2-|
inches long; leaves simple-, toothed; fruit round, resembling
a small apple, with thin flesh and bony nutlets — HAWTHORN
(Crataegus) .

W. Spines few, less than 1 inch long; leaves elliptic, not
lobed — RIVER HAWTHORN (Crataegus rivularis Nutt.), page 57
WW, Spines many, 3/4 to 2\ inches long; leaves ovate, slightly
lobed,

X. Leaves slightly 3- to 7-lobcd, bright green and hair-
less; twigs mostly hairless — CERRO HAWTHORN (Crataegus
crythropoda Ashe), page 57.

XX. Leaves slightly 7” or 9-lobed, dark green above and
paler beneath, loosely hairy on both sides; twigs
hairy when young; not in Arizona — FIREBERRY HAWTHORN
( Crataegus chrysocarpa Ashe), page 56,

W. Twigs and spines not as above; leaves compound; fruit a pod
with beanlikc seeds — -LEGUME FAMILY (Loguminosae),

Y. Spines scattered singly along twigs, \ inch or less in
length.

Z. Spines straight, single at leaf bases (nodes); twigs,
branches, and bark blue green; leaves twice (bipin-
nately) compound, soon shedding; not in New Mexico—
BLUE PALOVERDE ( Cercidium floridum Benth.), page 69.

ZZ. Spines curved or hooked.

*a, Twigs slender, reddish brown or purplish, bearing
stout, hooked, reddish spines scattered and not at
nodes,* leaves twice (bipinnately) compound; seeds
dark brown; CATCLAW ACACIA (Acacia greggii A. Gray),
page 63.

aa. Twigs thick, brittle, light tan, bearing many
hooked spines single (sometimes paired) below
leaf bases and leaf scars (nodes); leaves with
spiny leafstalk and 3 triangular leaflets borne
in summer; seeds bright red — SOUTHWESTERN CORAL-
BEAN (Erythrina flab ellif ormis Kearney), page 73*

YY* Spines paired at leaf bases and leaf sc -ns (nodes),

1/8 to | inch or more in length.

b. Nodes with a third, larger spine ending the very short
leaf axis; leaves twice (bipinnately) compound with 1
to 3 pairs of flattened, narrow, evergreen "streamers"
8 to 20 inches long and many short-lived leaflets —
JERUSALEM-THORN (parkinsonia aculcata L«), page 67.
bb. Nodes with only 2 spines; leaves without c-vergreen
"streamers,"

c. Spines white, straight, slender, mostly 1/8 to |r
inch long; leaves twice (bipinnately) compound
with 3 to 6 pairs of divisions, each with 10 to 25
pairs of leaflets; not in New Mexico — SWEET ACACIA
(Acacia fames iana (L.) Willd, ), page 64,
cc. Spines otherwise; leaves with fewer leaflets,

d. Leaves twice (bipinnately) compound; pod not
splitting open, thick and slightly sweet—
MESQUITE (Prosopis),

a. Paired spines separate; short knotlike spurs
^ to g inch in diameter developing at alder
nodes; pxl slightly flattened, 3 to 8 inches
long — -MESQUITE (Prosopis juli flora (Sw.) DC.)

page 65,

ee. Paired spines united in a stalklike base

bearing leafstalk; pod tightly coiled like a
large screw, 1 to l| inches long — FREMONT
SCREWBEAN (prosopis pubescens Benth.), page
66,

dd. Leaves once (p innately) compound; pod splitting
open, thin-walled,

f. Twigs brown, with brown or reddish stout
paired spines ^ to | inch long; leaves
deciduous; leaflets thin, bristle-tipped — •
NEW MEXICAN LOCUST (Robinia neo-mexicana
A, Gray), page 72,

ff • "Twigs green or gray, becoming light brown,
with stout gray to brown paired spines ^ to
3/8 inch long; leaves evergreen or nearly so
leaflets thick, not bristle-tipped; not in
New Mexico — TESOTA (Olneya tesota A. Gray),
page 72.

- 10 -

P4RT 4, KEY TO SPINELESS H4RDTOGDS (DICOTYLEDONS)

Trees without spines on branches, twigs, and leaves” leaves
deciduous or evergreen, mostly broad and flat, (Tho 5 species with
spiny-toothed leaves are included in both Parts 3 and 4.)

Note; Use this key if leaves are present (after leaves are
shed, old leaves often can be found on some twigs or on the ground).

If leaves are absent, use Part 5> page 20,

4. Leaves very small and crowded, less than \ inch long, scalelike or
divided into 3 to 7 very narrow lobes.

B. Leaves about 1/16 inch long, scalelike — FRENCH T4M4RISK (Tamarix
gallic a L. ) , page 86,

BB, Leaves p to g inch long, wedge-shaped and divided into 3 to 7 very
narrow lobes, thick with edges rolled under, with white resinous
dots, evergreen— CLIFFROSE (Cowiania stansburiana Torr.), page 58.
4, Loaves more than -g inch long, variously arranged, neither scaleliko
nor with narrow lobes.

C, Leaves very narrow, more than 20 times as long as wide, 3 to 6
inches long, simple, mostly single (alternate) but partly paired
(opposite) or in 3 ’ o— DESERTTYILLOW (Chilopsis linearis (Cav.)
Sweet), page 102,

CC. Leaves less than 10 times as long as broad, simple or divided into
leaflet s (compound) ,

D. Leaves and some twigs in pairs (opposite).

E. Leaves or the 3 or 5 leaflets coarsely and irregularly
tecthod, '.with veins extending to teeth; fruits paired,
clustered, long-winged "keys" — -M4PLE ( 4cer) .

F. Trigs greenish; leaves compound with 3 or sometimes 5
leaflets, end leaflet stalked — INL4MD BOEELDEE (4cor
negundo L. var. inter ius (Britton) Sa rg . ) , page 80,

FF, Twigs reddish to brown; loaves simple or compound with
3 leaflets and end leaflet stalkless.

G# Leaves 3- or 5-lobed or with 3 leaflets, edges

sharplj' and doubly saw-toothed — ROCKY MOUNTAIN M4PLE
(4cer glabrum Torr.)> page 80,

GG. Leaves 3~lobed, edges with a few large blunt teeth —
BIGTOOTH TI4PLE (4cor grandidentatum Nutt . ) , page 81,
EE. Leaves or lc- flats not coarsely toothed, with veins curved
within edges,

H. Loaves simple, ovate or elliptical, not toothed, with
about 5 long, curved veins on each side of midrib —
RED-OSIER D0GT00D (Cornus stolonifera Michx, ), page 95*
HH. Leaves compound with 2 to 9 leaflets or if simple not
as above.

I. Leaves compound with finely saw-toothed leaflets;
twigs with largo pith — ELDER (Sambucus) ♦

J. Leaflets 3 or 5> thick, evergreen — -MEXIC4N ELDER
(Sambucus mexicana Presl.), page 103.

JJ. Leaflets 5 to 9j thin or thick, deciduous —

BLUEBERRY ELDER (Sambucus glauca Nutt,), page 104,

- 11 -

II. Leaves compound or simple; leaflets or leaves bluntly
or coarsely toothed or without tooth,

K. Loaves less than 1 inch long, simple, with tooth-
less edges slightly rolled under, evergreen;
fruits egg-shaped, h. to 3/8 inch long; not in New
Moxic o— -DESERT-OLIVE FORESTIERA (Fores tier a
phillyreoides (Benth.) Torr.), page 101,

KK, Leaves more than 1 inch long; fruits clustered but
not paired, long-winged "keys" — ASH (Fraxinus) .

L , Tw ig s 4-an gl ed ,

M. Lcsivos simple or occasionally with 2 or 3
leaflets, rounded or short-pointed at apex —
SINGLELEAF ASH (Fraxinus anomala Torr,),
page 98,

1M, Leaves compound with 3 to 7 leaflets, long-
or short-pointed; not in Now Mexico — -LOWELL
ASH (Fraxinus lowellii Snrg, ) , page 98.

LL, Trigs round or rounded.

N. Leaflets mostly rounded at apex, with veins
inconspicuous; loaf axis narrowly winged;
nearly evergreen; not in New Mexico — GREGG
ASH (Fraxinus greggii A. Gray), page 99 •

NN. Leaflets pointed, with veins conspicuous;
leaf axis usually not winged,

0, Leaflets mostly loss than \ inch wide,
long-stalked (leaves occasionally simple
in a variety) — FRAGRANT ASH (Fraxinus
cuspidate Torr.), page 99*

00. Leaflets | to l| inches wide, short- or
long-stalked — -VELVET ASH (Fraxinus
velutina Torr.), page 100.

DD. Leaves and twigs single (alternate) or leaves crowded together.

P. Leaves divided into 3 to many leaflets (compound.), the
leaflets attached along the extended leafstalk or axis,

Q. Leaves twice (bipinnately) compound with 4 to 9 pairs of
featherlike divisions bearing numerous leaflets \ inch
long; not in Now Mexico — LITTLELEAF LYSILOMA (Lysiloma
microphylla Benth.), page 63.

QQ. Leaves once (pinnatoly) compound; leaflets fewer and larger,

R. Leaflets 3 or 5*

S, Leaflets 3* long-pointed, slightly wavy toothed or
without teeth, with many minute clear dots, not ever-
green; loaves and twigs strong scented when crushed —
HOPTREE (Ptelea).

T. Twigs straw-colored to greenish yellow; leaflets
mostly more than 3 times as long as wide — PALE
HOPTREE (Ptelea pallida Greene), page 73.

TT. Twigs brown or dark purple; leaflets mostly loss
than 3 tines as long as wide — -NARROWLEAF HOPTREE
(Ptelea angustif olia Benth.), page TA-
SS. Leaflets 3 5j short-pointed, edges without teeth,
thick and evergreen — HEARNS SUMAC (Rhus choriophylla
Wo ot and S t andl . ) , pa ge 78 .

- 12 -

RR. Leaflets more than 5t

U, Leaflets with long narrow tapering points,
one-sided,

V, Leaflets with saw-toothed edges and character-
istic walnut odor; fruit an edible walnut —

WALNUT (Julians).

W, Leaflets usually 17 to 23, narrowly lance-
shaped, less than \ inch wide; walnut fruit
h to 3/4 inches in diameter; not in Arizona —
LITTLE WALNUT (Ju, plans microcarpa Borland. ),
page 42.

WW, Leaflets usually 9 to 13, lance-shaped or
broadly lance-shaped, mostly more than 3/4
inch wide; walnut fruit 1 to l| inches in
diameter — ARIZONA WALNUT ( Juglans ma.jor
(Torr.) Heller), page 43.

W. Leaflets with edges not toothed; fruits

yellow, berrylike, ^ inch in diameter — WESTERN
SOAPBERRY (Sapindus drummondi Hook & Arn.),
page 82,

UU. Leaflets rounded, slightly notched, or blunt
pointed at apex, symmetrical,

X. Leaves with axis not winged,

Y, Leaflets 7 to 13, 3/4 to 2 inches long,
shiny, leathery and evergreen; not in
Arizona — MESCALBEAN (Sophora secundiflora
(Ortega) Lag.), page 70,

YY, Leaflets about 11 to 45, 3/S to 3/4 inch

long, gray green with conspicuous brown dots
beneath, resinous and with disagreeable odor —
KIDNEYTIOOD (Eysenhardtia polystactya (Ortega)
Sarg.), PagG 70.

XX, Leaves with winged axis, aromatic — BUESERA
(Burscra) »

Z, Leaflets 5 to 11, lance-shaped, \ to lg
inches long; not in Mow Mexico — FRAGRANT
BURSERA (Bursera odorata T, S, Brandegee),
page 75.

ZZ. Leaflets 15 to 30? narrowly oblong, about
p inch long; not in New Mexico — ELEPHAMTTREE
(Bursera mjcrophylla A. Gray), page 76.

PP, Leaves not divided into leaflet s' (simple),

a. Leaves with 3 or more main veins from base.

b. Loaves more than 6 inches long and wide, deeply
divided into 3 to 10 long-pointed lobes,

c. Leaves heart-shaped at base, edges mostly without
teeth — ARIZONA SYCAMORE (Plat anus wrightii S. Wats,),
page 54.

cc. Leaves with blade surrounding end of leafstalk,

edges saw-toothed; naturalized in Arizona but not in
Now Mexico — CASTOR -BEAN (Ricinus communis L,), page

76.

bb. Leaves less than 4 inches long, lobes short-pointed or
none .

d. Leaves rounded or blunt-pointed at apex, about as
broad as long.

- 13 ~

c. Leaves to 4 inches long and wide, nearly
round, not lobed; not in New Mexico — CALIFORNIA
REDBUD (Cercis occidentalis Torr.), page 67.
oe. Leaves J to lg inches long and wide, usually

3-lobed, evergreen; not in New Mexico — -CALIFORNIA
FREMONT IA (Fremontodendron calif ornicum (Torr,)
Cov,), page 86>.

dd. Leaves sharp-pointed, about twico as long as wide,
f, Leaves usually thick, not lobed, edges without
teeth or sometimes coarsely saw-toothed —

NETLEAF HACKBERRY (Celtis reticulata Torr,),
page 53,

ff. Loaves thin, often 3- to 5-lobecl, edges coarsely
saw-toothed — TEXAS MULBERRY (Morus microphylla
Buckl. ) , page 54*

aa, Leaves with a single main vein (midrib),

g. Juice milky, poisonous; not in New Mexico — JUMPING

BEAN SAPIUM (S?,pium bilocular e (S.Wats.) Pax), page 77*
gg. Juice watery,

h, Y/intcr buds 3 or more in cluster at tip of twig;
pith of twigs star-shaped in cross section; fruit
an acorn — OAK (Qucrcus).

i. Leaves deeply or shallowly lobed,

j, Leaves deeply 7- to 11-1 obed halfway or more
to middle, deciduous — GAMBEL OAK (Qucrcus
gambelii Nutt,), page 50,
jj. Leaves shallowly lobed.

k. Leaves more than 2\ inches long, long- or
short-pointed, thin and deciduous; not in
Arizona — CHINQUAPIN OAK (Qucrcus muehlon-
bergii Engelm, ), page 50,
kk. Leaves mostly less than 2\ inches long,
short-pointed, thick and evergreen —
WAVYLEAF OAK (Qucrcus undulata Torr,),
pBgo 49*

ii. Leaves not lobed, edges toothed or without
teeth, evergreen or nearly so.

1. Veins slightly sunken on upper surface and
prominently raised on lower surface,

m. Leaves densely white woolly beneath, sharp-
pointed and usually without teeth, edges
rolled under — SILVERLEAF OAK (Qucrcus
hypoleucoidcs A. Camus), page 52®
mm. Leaves hairy beneath, rounded or short —
pointed and toothed toward apex, edges
not rolled under,

n. Leaves slightly curved and concave

beneath, teeth conspicuous and spiny —
NETLEAF OAK (Qucrcus reticulata
Humb. & Bonpl.), page 46,
nn» Leaves flat, teeth small and inconspicu-
ous— ARIZONA P/HITE OAK (Qucrcus arizonica
Sarg.), page 47.

11, Veins not sunken on upper surface and only
slightly raised on lower surface,

o. Leaves with many spiny teeth,

- 14 -

p. Leaves blue green above, yellowish
green beneath, mostly less than 1 inch
long — SHRUB LIVE O/iK (Qucrcus turbi-
nella Greene), page 48.

pp. Leaves shiny ycllovj green above,

yellowish or whitish beneath, mostly
more than 1 inch long— PALMER OAK
(Quercus chrysolepis Liehm, var,
palmer i(Eng'elmV) Sarg. ) , page 51.
oo, Leaves with few small teeth or none*
q» Leaves blue green*

r. Leaves rounded at apex, without hairs
at maturity — -MEXICAN BLUE OAK (Quercus
oblongifolia Torr.), page 46*

rr, Leaves blunt or short-pointed, at

apex, densely hairy beneath — GRAY OAK
(Quercus grisea Liebm. ), page 48.
qq. Leaves shiny yellow green.

s. Leaves less than 1 inch long; not in
New Mexico — TOUIiEY OAK (Quercus
tourney i Sarg.), page 48.

ss. Leaves more than 1 inch long — EMORY
OAK (Quercus emoryi Torr*), page 52,
hh. Winter buds 1 or none at tip of twig; pith of twigs
mostly round or nearly so in cross section (in a
few species 3- or 5-angled); fruit not an acorn,

t. Leaves thick, evergreen, with edges flat or
turned under.

u. Leaves densely and finely hairy beneath.

v. Leaf edges flat, irregularly saw-toothed —
TORREY VAUQUELINIA (Vnuquolinia calif ornica
(Torr.) Sarg.), page 55*

w. Leaf edges rolled or turned under, with or
without teeth,

w« Leaves more than 1-/ inches long, edges
finely and inconspicuously toothed,
fruit a berry 3/8 inch in diameter —
CALIFORNIA BUCKTHORN (Rhamnus cali-
f ornica Eschsch var. ursina (Greene)
McMinn) , page 84,

ww. Leaves less than 1^ inches long; fruit
with a twisted hairy tail 1-g to 3 inches
long — MOUNTAIN-MAHOGANY (Cor cocarpus) .

x. Leaves shiny and leathery, edges
without teeth and strongly rolled
under; not in New Mexico — CURLLEAF
MOUNT A IN-MA HOGANY ( Cercocarpus ledi-
f-0lius Nutt.), page 58,
xx. Leaves not shiny or leathery, edges
toothed above middle and slightly
turned under.

y. Leaf edges with few rounded teeth
near apex— HAIRY MOUNTAIN MAHOGANY
(Cercocarpus br eviflorus A. Gray),
page 59.

- 15 ~

yy, Leaf edges finely toothed above
middle with pointed teeth; not in
New Mexico— BIRCHLEAF MOUNTAIN-
HAHOGANY (Corcocarpus bctuloidos
Nutt.), page 5b,

uu* Leaves hairless or nearly so*

z# Leaves spiny-toothed, oval to nearly round,
hollylike; not in New Mexico — -HOLLYLEAF
BUCKTHORN (Rhamnus crocea Nutt, var*
ilicifolia (Kellogg1) Greene), page 84*
zz. Leaves not spiny and without teeth (or
sometimes toothed in madrono), somewhat
longer than broad,

A. Twigs red, finely hairy when jroung,
becoming reddish brown and scaly —

MADRONE (Arbutus),

B. Leaves lance-shaped, short-pointed —

ARIZONA MADRONE ( Arbutus arizonica
(A. Gray) Sarg*), page 95,

BB. Leaves oval to lance-shaped, rounded
or short-pointed at apex; not in
Arizona— TEXAS MADRONE (Arbutus
texana Buckl,), page 96,

AA. Twigs not reddish and not scaly.

C. Twigs and leaves blue green; leaves
not leathery — TREE TOBACCO (Nicotiana
glauca Graham), page 101,

CC. Twigs brown or gray; leaves leathery —

SUMAC (Rhus) .

D. Leaves short-pointed, not flat but
curved upward at midrib, shiny light
green on both sides; not in New Mexico —
SUGAR SUMAC (Rhus ovata S. W&ts,),

page 78,

DP. Leaves rounded or blunt-pointed at apex,
flattened, dark, .green above with whitish
veils; Tinajas Altas Mountains, Arizona,
and not in Now Mexico— KEARNEY SUMAC
(Rhus koarncyi Barkley), page 78.
tt. Leaves thin, deciduous, flat.

E. Loaf blades more than 3 times as long as wide,
edges finely saw-toothed (or leaf blades broader
and edges without teeth).

F. Twigs slender, yellowish to red, purple or
brown; winter buds covered by a single scale;
seed capsule^ many on an upright axis (catkin)
and containing many cottony seeds — WILLOW (Salix) *

G. Leaves very narrow, less than 1 inch wide,
almost stalklcss,

H, Leaves less than 1^ inches long, slightly
hairy — YEWLEAF WILLOW (Salix taxifolia
H. B. K. ), page 39*

- 16 -

HH« Leaves 2 to 4 inches long, with
long silky white hairs pressed
against lower surface — COYOTE
WILLOW (Salix exigua Nutt,), page 30.

GG, Leaves more than l/4 inch wide, dis-
tinctly stalked,

I. Leaf edges finely sax'j-toothed;

leaves usually hairless at maturity,
Jjt Leaf edges with yellowish gland-
tipped teeth,

K, Leaves paler or whitish be-
neath— PACIFIC WILLOW (Salix
lasiandra Benth,), page 35 »

KK» Leaves green on both sides—
WHIPLASH WILLOW (Salix caudata
(Nutt,) Heller var, bryantiana
Ball & Bracelin), page 35 t
JJ, Leaf edges saw-toothed, but with-
out yellowish glands,

L, Leaves green on both sides —

GO CODING WILIOF (Salix
gooddingi Ball), page 36.

LL, Leaves paler or whitish be-
neath,

M, Leaves long-pointed,

N. Leaves broadest near

middle and tapering to
base; twigs red or purple
— BONPLAND WILLOW (Salix
bonplandiana H. B. K,
page 3S] ~

NN. Leaves broadost below

middle; twigs yellowish —
PEACHLEAF WILLOW (Salix
araygdaloid.es Anderss '17
page 37,

MM. Leaves short-pointed,

O. Leaves usually wedge-
shaped at base, 2 to 6
inches long; small or
medium-sized tree; not
in New Mexico — RED WIL-
LOW (Salix laevigata
Bebb), page 36,

00, Leaves broad and rounded
at base, 1 to 3 inches
long; usually shrubby —
YELLOW WILLOW (Salix
lutea Nutt,), page 40.

II. Leaf edges without teeth or slightly
wavy; leaves more or less white hairy
beneath*

P* Leaves about 5 times as long as
wide— ARROYO WILLOW (Salix lasio-
lepis Benth, ), page 40,

PP» Leaves less than 3 times as long
as wide.

- 17 -

£). Upper leaf surface yellcw
green or shiny, nearly hair-
less—SCOULER WILLOW (Salix
scou3.cria.nn B rrc.it), page 41*

QQ. Upper leaf surface dull green,
hairy — BEBB WILLOW (Snlix
bebbinnn Sarg. ) , page 41 »

FF. Twigs stout, yellowish but becoming light
gray; winter buds with about 5 scales
exposed, resinous — -NARROWLEAF COTTONWOOD
(Populus nngustif olin Janes), page 31*

EE. Leaf blades less than 3 tines ns long ns
wide, edges coarsely or finely toothed.

R. Leafstalks flattened, long, slender, about
as long as leaf blade; leaf edges with
curved teeth; seed capsules many on a
drooping .axis (catkin) and containing many
cottony seeds — COTTONIiDOD, ASPEN (Fopulus) .

S. Leaf blades nearly round, finely
toothed — QUAKING ASPEN (Populus
trcmuloides Michx. ), page 32.

SS. Leaf blades broacHy triangular,
coarsely saw-toothed.

T. Leaf blades long-pointed; not in
Arizona— PLA BIS COTTONWOOD
(Fopulus sargentii Dode) , page 34.

TT. Leaf blades short-pointed.

U. Leaf blades mostly abruptly
short-pointed; seed capsules
narrow and mostly shorter than
stalks; not in Arizona — 'RIO GRANDE
COTTONWOOD (Populus wislizeni
S. Wats.) Sarg.), page 34*

UU. Leaf blades mostly bluntly short-
pointed; seed capsules egg-shaped
and longer than stalks — -FREMONT
COTTON I'OOD (Populus fremontii S.

Wats.), page 33*

RR. Leafstalks round, short, less than half as long
as leaf blade; leaf edges coarsely or finely saw-
toothed; seeds not cottony and not borne in capsules.

V. Leaf edges usually doubly saw-toothed with
alternating teeth mostly uneven; fruit dry,
conolike.

W. Young twigs with some glandular hairs or gland
dots; conelike fruit papery or membranous,

X. Leaves hairy beneath; twigs with glandular
hairs; conelike fruit of baglike, papery
bracts— KNOWLTON HOPHORNBEAM (Ostrya
knowltoni Cov,), page 44*

XX. Loaves not hairy; twigs with many gland
dots; cone fruit with membranous scales —
WATER BIRCH (Bctula occidentalis Hook.),
page 44,

- 18 -

WI7. Young twigs hairy or hairless but
not glandular; cone fruit with hard
black scales, remaining on tree in
winter — ALDER (Alnus),

Y, Leaves slightly lobed, with
rounded, straight, or slightly
heart-shaped base — THINLEAF ALDER
(Alnus tonuifolia Nutt,), page 45*

YY, Leaves mostly not lobed, gradually
narrowed at base — ARIZONA ALDER
( Alnus oblongifolia Torr.), page 45*
W. Loaf edges with uniform teeth; fruit juicy,
round,

Z. Leaves nearly round to elliptic,

edges coarsely toothed above middle —
UTAH SERVICE BERRY (Amelanchier
utahensi3 Koehno), page” 56,

ZZ. Loaves about twice as long as wide,

edges finely toothed from base to apex,
a. Leafstalks, young twigs, and naked
buds with dense coat of minute
light brown hairs — BIRCHLEAF
BUCKTHORN (Rhamnus betulaefolia
Greene), page 85*

a a. Leafstalks, young twigs, and buds
hairless or slightly gray hairy —
CHERRY, CHOKECHERRY, PLUM (Prunus),
b. Leaves long-pointed at apex,
appearing slightly wrinkled,
with veins raised beneath; not
native in Arizona — -AMERICAN PLUM
(Prunus americana Marsh,), page 62,
bb. Leaves short-pointed or rounded
at apex, flat, with veins not
raised beneath*,
c , Leaves not shiny above,
edges with blunt gland-
tipped teeth— BITTER CHERRY
(Frunus emarginata (Dougl.)

D, Dietr,), page 6o,
cc. Leaves shiny above, edges
sharply saw-toothed,
d. Loaf blades rounded or
heart-shaped at base,
whitish b eneath — COMMON
CHOKECHERRY (Prunus
virginiana L. ), page 61,
dd. Leaf blades short-pointed
at base, only slightly
paler beneath — SOU THWES TERN
CHOKECHERRY (Prunus virens
(Woot* & Standl^y Shreve),
page 62.

- 19

PART 5, WINTER KEY TO DECIDUOUS SPINELESS HARDWOODS (DICOTYLEDONS)

Note: Use this key for trees with neither leaves nor spines. If

old leaves are found on some twigs or on the ground, it may be easier to
use Part page 11, All species of Part 5 are also in Part 4*

A, Scale leaves l/l6 inch long or their broken bases remaining attached
singly (alternate) on slender reddish or yellowish twigs ; leaf scars
absent (leafy twigs shedding and leaving a round twig scar) — -FRENCH
TAMARISK ( Tamar ix gallica L«), page 86.

AA, Scale leaves absent; leaf scars from larger leaves present,

B, Leaf scars and winter buds mostly single (alternate) but partly
paired (opposite) or in 3* s; leaf scars with 1 dotlike bundle
scar; fruit a very long and narrow seed capsule or pod 4 to 10
inches long, remaining attached in winter — -DESERTWILLOW
(Chilopsis linearis (Cav.) Sweet), page 102,

BB, Leaf scars and winter buds either all paired (opposite) or all

single (alternate) or sometimes crowded together; loaf scars with
3 or more dotlike bundle scars; individual fruits less than 2
inches long, variously shaped.

C* Leaf scars, winter buds, and some twigs in pairs (opposite),

D. Twigs with large, soft pith-— BLUEBERRY ELDER (Sambucus
glauca Nutt.), page 104*

DD, Twigs with small pith.

E. Winter buds mostly pointed; leaf scars small, with 3
bundle scars,

F. Winter buds stalked; some bases of leafstalks remain-
ing attached and covering leaf scars; twigs purplish
red-— RED -OSIER DOGWOOD ( Cornus stolonifera Michx. ) ,
page 95,

FF, Winter buds not stalked; bases of leafstalks not

remaining attached; twigs greenish or red to brown—
MAPLE; BOXELDER (Acer).

G, Twigs greenish — INLAND BOXELDER (Acer negundo L.
var. inter ius (Britton) Sarg.), page 80.

GG. Twigs red to brown.

H. Winter buds of 2 scales meeting at edges, hair-
less—ROCKY MOUNTAIN MAPLE (Acer glabrum Torr,),
page 80.

HH. Winter buds of 4 or more overlapping scales,
slightly hairy — BIGTOOTH MAPLE (Acer grandiden-
tatum Nutt.), page 81.

EE, Winter buds rounded or blunt; leaf scars relatively
largo, nearly half round, with many bundle scars — ASH
(Fraxinus) ,

I, Twigs 4-angled,

J. Leaf scars mostly less than l/8 inch wide — .

SINGLELEAF ASH ( Fraxinus anomala Torr.), page 98.
JJ, Leaf scars mostly more than l/S inch wide; not in
New Mexico — DOWELL ASH (Fraxinus lowellii Sarg.),
page 98.

II. Twigs round or rounded.

- 20 -

K. Leaf scars raised; winter buds dark brown; twigs
slender, hairless — FRAGRANT ASH ( Fraxinus cuspidata
Torr . ), page 99.

KK* Leaf scars not raised; winter buds brown; twigs
mostly stout, hairy or hairless — -VELVET ASH
(Fraxinus vein tine Torr.), page 100
CC. Leaf scars, winter buc’s, and twigs single (alternate) or some-
times crowded together,

L, Winter buds apparently not compared of scales,

M. Winter buds naked, composed of minute immature leaves
densely covered with short light brown hairs — B3RCHLEAF
BUCKTHORN ( P.hamnus bctulao folia Qrcenc), page 85*

I'M, Winter buds sunken, appearing as a tuft of pale yellow
silky hairs in a horseshoe-shaped leaf scar; twigs with
strong odor when crushed — HOPTRSE (Ptclea) •

N. Twigs straw-colored to greenish yellow — PALE HOPTRSE
(Ptelea pallida Greene), page 73c
NN. Twigs brown or dark purple — NARROVLEAF HOPTRSE (Ptelea
angustif olla Be nth. ) , page 74*

LL, Winter buds covered by one or more scales,

0, Vinter buds 3 or more in cluster at tip of twig; pith of
twigs star-shaped in cross section; fruit an acorn — OAK
(Qucrcus) .

P, Twigs slightly hairy toward tip — GAMBEL OAK (Quercus
gambelii Nutt. ) , page 50,

PP. Twigs not hairy; rare and local in New Mexico and not
in Arizona — CHINQUAPIN OAK (Quercus muehlenbergii
Eng elm, ), page 50,

00. Winter buds 1 or none at tip of twig; pith of twigs
mostly round or nearly so in cross section (in a few
species 3~ or 5-angled) ; fruit not an acorn,

Q, Twigs more or less zig-zag, with leaf scars and winter
buds in 2 vertical rows along twig.

R. Winter buds covered by a single exposed scale;

leaf scar ring-shaped and surrounding winter bud—
ARIZONA SYCAMORE (Platanus wrightii S, Wats,), page 54 •
RR. Winter buds with 2 or more scales exposed; leaf
scar sh^rt at base of winter bud,

S, Winter buds pressed closely against twig; pith
with partitions (chambered) — NETLEAF HACKBERRY
(Ccltis reticulata Torr,), page 53 •

SS, Winter buds spreading from twig; pith solid,

T, Twigs with hairs or glands near tip,

U, Twigs hairy and with some glandular hairs—
KNOWLTON HOP HORNBEAM (Ostrya knowltoni
Cov,), page 44«

UU. Twigs with many gland dots — -WATER BIRCH
(Bctula Occident alls Hook,), page 44.

TT. Twigs without hairs or glands; not in Now

Mexico — CALIFORNIA REDBUD (Cercis occidental is
Torr.), page 67.

- 21 -

QQ. Twigs straight or curved, not zig-zag, with leaf scars
and winter buds in more than 2 vertical rows along
twig,

V. Winter buds covered by a single exposed scale;

twigs mostly slender — WILLOW (Salix; the different
species not readily distinguished in winter condition),
W, Winter buds with 2 or more scales exposed.

W. Winter buds stalked, of 2 or 3 scales meeting at
their edges; fruit a black cone remaining on
tree in winter — ALDER (Alnus) .

X. Twigs finely hairy toward tip; winter buds
slightly hairy- — THINLEAF ALDER ( Alnus tenui-
fol:.-? Nutt « ) , page 45 *

XX, Twigs and winter buds hairless or nearly so —
ARIZONA ALDER (Air us oblongifolia Torr,),
page 45*

YJW. Winter buds not stalked, of overlapping scales;
fruit not a cone,

Y* Winter buds of inconspicuous scales, mostly
rounded, short, and small*

Z, Winter buds and young twigs hairy; bark
rough or scaly,

a. Young twigs bearing many dots,

b, Yeung twigs brown with brown gland
dots; 2 needlc-like scales (stip-
ules) l/3 inch long present at some
leaf scars — KIDNEYWOGD (Eysenhardtta
polystachya (Crwega) SargT), page 70,

bb. Young twigs reddish brown with many
light brown dots (lenticels); with-
out scales (stipules) at leaf scars —
LITTLELEAF LYSILOHA (Lysiloma
microphylla Benth. ), page 63.
aa. Young twigs not dotted; buds often 2
together (superposed), 1 above the
other at a leaf scar,

c. Buds gray; twigs brown or gray, with
characteristic walnut odor; pith
brown, with partitions (chambered) —
WALNUT (Ju plans) .

d. Tree small or shrubby, usually
branching near ground; walnut
fruit g to 3/4 inch in diameter;
not in Arizona — LITTLE WALNUT'

( Ju, plans microcarpa Borland.),
page 42.

dd. Tree small to medium-sized, with
trunks branched above; walnut
fruit 1 to 1-| inches in diameter —
ARIZONA WALNUT ( Juglans major
(Torr.) Heller), page 43*

- 22

cc. Buds yellow to brown; twigs yellow
green, becoming gray; pith pale
yellow, solid— WESTERN SOAPBERRY
(Sapindus drummondi Hook. & Arn.),
page 82,

ZZ. Winter buds and twigs without hairs; bark
papery; strongly aromatic trees — BURS ERA
(Burscra) .

e. Twigs bright green (brown in dried
specimens); not in Now Mexico —

FRAGRANT BURSERA (Burscra odorata T. S.
Brandegce), page 75.

ec, Twigs reddish brown; not in New Mexico —
ELEPHANTTREE (Burs era raicrophylla
A. Gray), page 76,

YY, Winter buds of conspicuous scales, mostly
pointed and long,

f. Winter buds resinous or sticky, shiny;
lowest bud scale centered over loaf scar
(directly in front); twigs stout, mostly
light gray— COTTONWOOD, ASPEN (Populus),

g. Winter buds ^ inch or less in length,
short -pointed, only slightly resinous —
QUAKING ASPEN (Populus trcmuloides
Michx. ), page 32.

gg. Winter buds more than 3/8 inch long,
long-pointed, very resinous,

h. Winter buds hairless or nearly so,
young twigs yellowish; tree of
mountain zones — -NARROWLEAF COTTON-
WOOD (Populus angustifolia James),
page 31,

hh. Winter buds minutely hairy; young
twigs green to gray; trees chiefly
of desert and plains zones,

i. Tree of Great Plains region in
northeastern New Mexico; not in
Ar iz ona — -PLAINS COTTONWOOD
(Populus sargent ii Dode)^ page 34.
ii. Tree of Southwest.

j. Tree of western half of New
Mexico; not in Arizona — RIO
GRANDE COTTONWOOD (Populus
wislizeni (S . Wat s . ) Sarg . ) ,
page 34.

jj. Tree of Arizona and southwest-
ern New Mexico — FREMONT
COTTONWOOD (Populus fremontii
S. Wats,), page 33«

ff. Winter buds not resinous or sticky; lowest
bud scales at side of bud; twigs slender,
purplish, reddish, gray, or brown.

- 23 -

k* Winter buds slightly one-sided; leaf
scars round or nearly so; twigs light
brown, finely hairy toward tip —

TEXAS MULBERRY (Morns microphylla
Buckl. ) , page 54,

kk. Winter buds not one-sided; leaf scars
much broader than high; twigs darker,
purplish or reddish to gray, hairless
or hairy,

1, Leaf scars narrowly crescent-shaped;
winter buds long-pointed, with
loosely arranged pointed scales —
UTAH SERVICE BERRY ( Amelanchier
utahensis Koehne), page 5<e*

11* Leaf scars half-round or half-
elliptical; winter buds short-
pointed, with regularly overlapping
rounded scales— CHERRY, CHOKECHERRY,
PLUM (Prunus),

m. Terminal bud absent at end of
twig; twigs stout and stiff,
widely spreading, the short
lateral twigs often ending in
spines; not native in Arizona —
AMERICAN PLUM (prunus amor ic ana
Marsh*), page 62c

mm* Terminal bud present at end of
twig; twigs slender, not ending
in spines ,

n. Twigs often slightly hairy
near tip; usually a shrub less
than 13 feet tall— BITTER
CHERRY (Prunus emarginata
Dougl,) D. Dietr*), page 60*
nn, Twigs mostly hairless,

o* Shrub or small tree to 25
feet tall and about 6 inches
in trunk diameter, often
forming dense thickets;
leaves deciduous — COMMON
CHOKECHERRY (Prunus virgini-
ana L. ), page 61,
oo. Small to medium-sized tree
to 40 feet tall and 2 feet
in trunk diameter or large
shrub; leaves nearly ever-
green--^ OUTHWESTERN CHOKE-
CHERRY (Prunus virens
(.Woot. & Standi.) Shrove),
page 62.

- 24 -

LIST OF SPECIES OF SOUTHWFS TERN TREES

The 135 tree species in this key are listed below by plant families
in the usual botanical order. Page numbers refer to descriptions in the
handbook, Southwestern Trees. The 99 tree species found in New Mexico are
designated by an asterisk (*) and the 126 in Arizona by a dagger (/) .

Pine family (Pinaceae) , page 10.

* /Mexican pinyon (Pinus cembroides Zucc.), page 10.

* /pinyon (Pinus edulis Engelm.) , page 11.

/singleleaf pinyon (Pinus monophylla Torr. & Frem.), page 12.
*/bristlecone pine (Pinus aristata Engelm.), page 13.

Climber pine (pinus flexilis James) , page 13.

* /Chihuahua pine (Pinus leiophylla Schiede & Deppe var. chihuahuana
(Engelm.) Shaw), page 14.

Vponderosa pine (Pinus ponderosa Laws . ) , page 15.

* /Apache pine (Pinus latifolia Sarg.) , page 16.

*/Engelmann spruce (Picea engelmanni Parry) , page 17.

*/blue spruce (Picea pungens Engelm.) , page 17.

*/Douglas-fir (Pseudotsuga taxifolia (Poir.) Britton), page 18,

>:</white fir (Abies concolor (Gord. & Glend.) Hoopes) , page 19.

*/alpine fir (Abies lasiocarpa (Hock.) Nutt.), page 20.

* /Arizona cypress (Cupressus arizonica Greene) , page 20.

* /alligator juniper' "(juniper us deppeana Steud.), page 22.

* /Rocky Mountain juniper (Juniperus scopulorum Sarg.) , page 22.

*/one-seed juniper (Juniperus mono sperm (Engelm.) Sarg.), page 23.

*/Utah juniper (Juniperus osteosperma (Torr.) Little, page 24.

Palm family (Palmae) , page 24.

/California washingtonia (Washingtonia filifera (Linden) H. Wendl.) ,
page 24.

Lily family (Liliaceao) , page 26.

*/soaptree yucca (Yucca elata Engelm.), page 26.

/joshua-tree (Yucca brevifolia Engelm.), page 27.

* /Schotts yucca (Yucca schottii Engelm.) , page 28.

/Mohave yucca (Yucca mohavensis Sarg.) , page 29.

*Torrey yucca (Yucca torreyi Shafer), page 30.

/Bigelow nolina (Nolina bigelovii (Torr.) S. Wats.), page 30.

Willow family (Salicaceae) , page 31.

*/narrowleaf cottonwood (Populus angustifolia James) , page 31
*/quaking aspen (Populus tremuloidos Michx.), page 32
* /Fremont cottonwood (Populus fremontii S. Wats.), page 33.

*Rio Grande cottonwood (Populus wislizoni (S. Wats.) Sarg.), page 34.
^plains cottonwood (Populus sargentii Dodo) , page 34.

*/pacific willow (Salix lasiandra Banth.), page 35.

*/whiplash willow (Salix caudata (Nutt.) Heller var. bryantiana Ball &
Bracelin) , page 35.

/red willow (Salix laevigata Bebb) , page 36.

*/Bonpland willoxv (Salix bonplandiana H. B. K.) , page 36.

*/Goodding willow (Salix gooddingi Ball) , pago 36.

*/peachleaf willow (Salix amygdaloides Anderss.), page 37,

* /coyote willow (Salix exigua Nutt.) , pago 38.

-25-

*/yewleaf willow (galix taxifolia H. B. K.), page 39,

* /yellow willow (galix lutea Nutt.), page 40.

*/arroyo willow (Salix lasiolepis Benth.), page 40’.

*/Scouler willow (salix scouleriana Barratt) , page 41.

*/Bebb willow (Salix bebbiana Sarg.), page 41,

Walnut family ( Juglandaceae) , page 42.

*little walnut (Juglans microcarpa Berland.), page 42,

* /Arizona walnut (Juglans major (Torr.) Heller), page 43.

Birch family (Betulaceae) , page 44,,

*/Knowlton hophornbeam (Qstrya knowltoni Cov.) , page 44.

* /water birch (Be tula occidentalis Hook.), page 44.

*/thinleaf alder (Alnus tenuifolia Nutt.), page 45.

^/Arizona alder (Alnus oblongif olia Torr.), page 45.

Beech family (Fagaceae) , page 46.

* /net leaf oak (Quercus_ reticulata Ilumb. & Bonpl.) , page 46.

* /Mexican blue oak (Quercus oblongif olia Torr.), page 46.

* /Arizona white oak (Quercus arizonica Sarg.), page 47.

*/gray oak (Quercus grisea Liebrn.), page 48.

/Tourney oak (Quercus toumeyi Sarg.), page 48.

*/shrub live oak (Quercus turbinella G-reene) , page 48.

*/wavyleaf oak (Quercus undulata Torr.), page 49.

^chinquapin oak (Q.uercus muehlenbergii Engelm.) , page 50.

* /(Jamb el oak (Quercus gambelii Nutt.), page 50.

*/Palmer oak (Quercus chrysolepis Liebrn . var. palmori (Engelm.) Sarg.),
page 51.

* /Emory oak (Quercus emoryi Torr.), page 52.

*/silverleaf oak (Quercus hypoleucoides A. Camus) , page 52.

Elm family (Ulmaceae) , page 53,

* /net leaf hackberry (Goltis reticulata Torr.), page 53.

Mulberry family (Moraceae) , page 54.

*/Toxas mulberry (Morus microphylla Buckl.), page 54.

Sycamore family (Platanaceae) , page 54.

* /Arizona sycamore (platanus wright ii S. Wats.), page 54.

Rose family (Rosaceae) , page 55,

*/Tcrrey vauquelinia (Vauquelinia californica (Torr.) Sarg., pago 55.

*/TJtah serviceberry (Amelanchier utahonsis Koehne) , page 56.

*fireberry hawthorn (Crataegus chrysocarpa Ashe) , page 56.

:;</river hawthorn (Crataegus rivularis Nutt.), page 57.

*/Corro hawthorn (Crataegus erythropoda Ashe) , pago 57.

*/cliffrose (Cowania stansburiana Torr.), page 58.

/curlleaf mountain-mahogany (Cercocarpus ledifolius Nutt.) , pago 58.
*/hairy mountain-mahogany (Qcrcocarpus broviflorus A. Gray), pago 59.

/birchleaf mountain-mahog.,.ny~~(cer"co'carpus betulo ides Nutt.), page 60.
^/bitter cherry (Prunus emarginata (Dougl.) D. Dietr.), page 60.

* /common chokecherry (Prunus virginiana L.), page 61.

^/southwestern chokecherry (Prunus virons (Woot .& Standi. ) Shrove), pago 62.
^American plum (Prunus amor ic ana Marsh-.), page 62.

-26-

Legume family (Leguminosao) , pago 63,

/little loaf lysiloma (Lysiloma microphylla Bonth.) , pago 63.
*/catclaw acacia (Acacia groggii a. Gray), pago 63.

/sweet acacia (Acacia fames iana (L.) Willd.), page 64.

* /mosquito (Prosopis juli flora ( Sw . ) DC.), pago 65.

*/Fremont screwboan (Prosopis pub o scons Bonth.), page 66.

/California redbud (Corcis occidentalis Torr.), pago 67.
*/Terusalem-thorn (Parkinsonla aculeate L.) , pago 67.

/yellow pa lover do (Ccrcidi'um microphyllum (Torr.) Rose & Johnst.),
page 68.

/blue palovcrdo (Ccrcidium floridum Bonth.), pigo 69.

*moscalboan (Sophora socundiflora ( Ortega) Lag.), page 70.
*/kidneywood (Eysonhardtia polystaohya (Ortega) Sarg.), page 70.

/smoke thorn (Dale a spinosa A. Gray) , pago 71 .

* /Now Mexican locust (Robinia neo-mexicana A. Gray), pago 72.

/tesota (Olneya tosota A. Gray), p .go 72.

* /southwestern coralboan (Erythrina f labolliformis Kearney) , page 73.

Rue family (Rutaceac) , page 73.

*/palo hoptree (Ptoloa pallida Greene) , page 73.

*/narrowloaf hoptree (Ptoloa angustifolia Bonth.), page 74.

Ailanthus family (Simaroubacoao) , page 74.

/holacantha (Holacantha omoryi A. Gray), pago 74.

Bursera family (Burseraceao) , page 75.

/fragrant bursera (Bursera o do rata T. S. Brmdcgoo), pago 75.
/elophanttree (Bursera microphylla A. Gray), pago 76.

Spurge family (Euphorbiacoae) , page 76.

/castor-bean (Ricinus communis L.), page 76.

/jumping -bean sapium (Sapium bilocularo (S. Wats.) Pax), page 77.

Cashew family (Anrcardiacoac) , page 78.

/sug .r sumac (Rhus ovate S. Wats.), page 78.

/k earncy sumac (Rhus kearnoyi Berkeley) , page 78.

*/Menrns sumac (Rhus choriophylla Moot . & Standi . ) , page 78 .

Bittersweet family (Colastracoae) , page 79.

/canotia ( C ano tie ho la cant ha Torr.), page 79.

Maple family (Aceraccae) , page 80.

"'/inland boxolder (Acer nogundo L. var. interius (Britton) Sarg.), page 80.
* /Rocky Mountain maple (Acer glabrum Torr . ) , page 80 .

*/bigtooth maple (Ac or gran di d cn t a t um Nutt.) , p .ge 81

Soapberry family (Sap indue cue) , page 82.

* /western soapberry (Sapindus drummondi Hook. & Arn.) , page 82,

Buckthorn family (Rhamnacoae) , page 83.

*/lotowood condalia (Condalia obtusifolia (Hook.) Weberb.), pago 83,
/bitter condalia (Condalia globosa Johnst.), page 83.

/hollyleaf buckthorn (Rhamnus crocea Nutt . var. ilicifolia (Kellogg)
Greene), pago 84.

-27-

* /California buckthorn (Rhamnus calif ornica Eschsch. var, ursina (Greene)
McMinn) , page 84.

*/birchleaf buckthorn (Rhamnus betulaefolia Greene) , page 85.

Sterculia family (Sterculiaceae) , page 86.

/California fremontia ( Fremontodendron californicum (Torr.) Cov.), page 86.

Tamarisk family ( Tamar icac eae ) , page 86.

/French tamarisk (Tamarix gallica L.) , page 86.

Allthorn family (Koeberliniaceae) , page 88.

* /allthorn (Koeberlinia spinosa Zucc.) , page 88.

Cactus family (Cactaceae) , page 88.

/saguaro (Cereus giganteus Engelm.) , page 88.

/organpipe cactus (Cereus thurberi Engelm.) , page 90.

/senita (Cereus schottii Engelm.) , page 91.

/jumping cholla (Opuntia fulgida Engelm.), page 92.

*/tasajo (Opuntia spinosior (Engelm.) Tourney), page 93.

/staghorn cholla (Opuntia versicolor Engelm.) , page 94.

/buckhorn cholla (Opuntia acanthocarpa Engelm. & Bigel.) , page 94.

Dogwood family (Cornaoeae) , page 95.

* /red-osier dogwood (Cornus stolonifera Mlchx. ) , page 95.

Heath family (Ericaceae), page 96.

* /Arizona madrone (Arbutus arizonica (A. Gray) Sarg.) , page 96.

*Texas madrone (Arbutus texana Buckl.) , page 96.

Sapote family (Sapotaceae) , page 97.

*/gum bumelia (Bumelia lanuginosa (Michx.) Pers . var. rigida A. Gray),
page 97.

Olive family (Oleaceae) , page 98.

"'"/singloleaf ash (Eraxinus anomala Torr.) , page 98.

/Lowell ash ( ^raxinus lowellii Sarg.), page 98.

* /fragrant ash (Eraxinus cusp! data Torr.) , page 99.

/Gregg ash (Eraxinus greggii A. Gray), page 99.

^/velvet ash (Eraxinus velutina Torr.), page 100.

/desert-olive forestiera" (Eorestiera phillyreoides (Benth.) Torr.,
page 101 „

Nightshade family (Solanaceae) , page 101.

*/tree tobacco (Nicotiana glauca Graham) , page 101.

Bignonia family (3ignoniaceac) , page 102.

*/dosortwillow (Chilopsis linearis (Cav.) Sweet) , page 102.

Honeysuckle family (Caprif oliacoae) , page 103.

* /Mexican older (Sambucus moxicana Prosl) , page 103.

* /blueberry elder (Sambucus glauca Nutt . ) , page 104.

-28-

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