BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Arbutus texana | Texas Madrone 



GENERAL BOTANICAL CHARACTERISTICS : 
Texas madrone grows as an evergreen tree or, less commonly, as a large
shrub which reaches 20 or 30 feet (0.6-1.1 m) in height [12].  Plants
may reach 40 feet (12 m) in height, 9.3 feet (2.8 m) in girth, and 42
feet (13 m) in crown spread on favorable sites [12,19].  Branches are
usually crooked, stout, and spreading [26].  Bark of Texas madrone is
both unique and attractive.  Older bark is dark brown, gray, or black
and exfoliates annually in papery layers to expose colorful new
"skinlike" bark [2,12,26].  New bark may be white, orange, pink,
apricot, tan, or dark red [22,26].

The simple, alternate leaves of Texas madrone are thick and leathery
[12,22,26].  Leaves are oblong to elliptic ovate to oval, dark green
above and paler beneath [22,26].  The upper surface is glabrous, whereas
the lower surface is glabrous or somewhat pubescent [26].

Small, urn-shaped white or pinkish-white blossoms occur in clusters or
panicles approximately 3 inches (8 cm) in length [12,22].  Fruits are
nearly round, warty "berries" 0.25 to 0.3 inch (6-8 mm) in diameter
[19,26].  Berries are bright red, yellow-orange, or yellow [22,26] and
are borne in 2- to 3-inch (5-8 cm) clusters [26].  Each fruit contains 1
to 10 small white seeds [26,31].


RAUNKIAER LIFE FORM : 
   Undisturbed State:  Phanerophyte (microphanerophyte)
   Undisturbed State:  Phanerophyte (mesophanerophyte)


REGENERATION PROCESSES : 
Seed:  Little is known about reproduction of Texas madrone [12].
However, this species is characterized by a low reproductive rate [23].
Seed is produced in abundance [26] and widely dispersed [19], but
seedlings are extremely rare.  Small numbers of seedlings have been
observed in Gardner State Park, the Guadalupe Mountains, and near
Devil's Backbone in Hays County, Texas [12].  A unique population of
several hundred seedlings reportedly exists near Vanderpool, Texas.

Germination:  If seed remains moist, germination can begin within 7 to
14 days [12].  Seedlings exhibit best early growth under a 12-hour
photoperiod at daytime temperatures of 81 degrees F (27 degrees C) and
nighttime temperatures of 64 degrees F (18 degrees C) [27,28].  Good
growth occurs at 60 to 70 percent relative humidity at a light intensity
of 6,500 to 10,000 lux [28].  At higher light intensities, growth may be
reduced by photo-bleaching of chlorophyll [27].  The effects of higher
light intensities may be somewhat mitigated under natural conditions if
soil moisture remains high [27].  Under ideal laboratory conditions,
germination can range from 20 to 90 percent [31].

Nurse trees:  On the Edwards Plateau, seedlings are most often found at
the base of junipers where juniper mulch is fairly thick [27].  Other
species can also serve as "nurse trees", but seedlings are rarely if
ever found beneath older madrones [12].  The partial shade of the nurse
trees reduces water stress and allows seedlings to survive despite dry
conditions [28].  The heavy mulch also promotes survival by holding
water.

Vegetative regeneration:  Under laboratory conditions, plants may be
propagated by cutting, layering, and budding [26].  Stump-sprouts have
been reported under natural conditions [31].


SITE CHARACTERISTICS : 
Texas madrone grows in wooded canyons, on slopes of desert mountains,
along dry creekbeds, and in foothill drainages with water present
[12,19].  It grows well in full sun on xeric sites [22,26].  Texas
madrone is a common component of closed-canopy canyon forests and
densely wooded stands which occur at the head of canyons [11].
Scattered individuals occur in oak-pinyon-juniper and madrean evergreen
woodlands, interior chaparral, and ponderosa pine (Pinus ponderosa)
communities [3,4,12,19,29,30].

Plant associates:  Common associates include the live oaks (Quercus
spp.), Graves oak (Q. gravesii), alligator juniper (Juniperus deppeana),
Ashe juniper (J. ashei), Mexican pinyon (Pinus cembroides), ponderosa
pine, and cedar elm (Ulmus crassifolia) [8,12].  Eastern cottonwood
(Populus deltoides), coyote willow (Salix exigua), gray oak (Quercus
grisea), bigtooth maple (Acer grandidentatum), and ash (Fraxinus spp.)
frequently occur with Texas madrone in riparian woodland communities
[4].

Soils:  Texas madrone grows on well-drained slightly acidic to alkaline
soils [22].  Soil pH commonly ranges from 7.5 to 7.8 [22].  Soils are
often derived from limestone or igneous parent materials [26].

Climate:  Average precipitation ranges from 16 to 30 inches (41-72 cm)
annually [31].

Elevation:  In Trans-Pecos Texas, Texas madrone grows from 4,000 to
7,500 feet (1,219-2,286 m) in elevation [19].


SUCCESSIONAL STATUS : 
Texas madrone is characterized by a low reproductive rate and slow
growth [23].  It occurs in relatively undisturbed climax riparian
woodland communities.  However, little is known about its successional
role in other communities in which it occurs.


SEASONAL DEVELOPMENT : 
Texas madrone flowers in early spring and berries ripen during the fall
[22].  Generalized flowering and fruiting dates by geographic location
are as follows:

location             flowering            fruiting          authority

Trans-Pecos TX       Feb. - April         ----              Powell 1988

SW                   Feb. - March         ----              Vines 1960

TX                   late Feb. -          Oct. - Dec.       Hardesty and
                     early March                            Whitenberg
                                                            1976

Related categories for Species: Arbutus texana | Texas Madrone