Index of Species Information
SPECIES: Ungnadia speciosa
SPECIES: Ungnadia speciosa
AUTHORSHIP AND CITATION :
Tirmenstein, D. A. 1990. Ungnadia speciosa. In: Fire Effects Information System, [Online].
U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station,
Fire Sciences Laboratory (Producer). Available:
SCS PLANT CODE :
COMMON NAMES :
New Mexican buckeye
New Mexico buckeye
The currently accepted scientific name of Mexican buckeye is Ungnadia
speciosa Endl. . Mexican buckeye is placed in the monotypic genus
Ungnadia  within the family Sapindaceae .
LIFE FORM :
FEDERAL LEGAL STATUS :
No special status
OTHER STATUS :
DISTRIBUTION AND OCCURRENCE
SPECIES: Ungnadia speciosa
GENERAL DISTRIBUTION :
Mexican buckeye grows from the Edwards Plateau of south-central Texas
west to Trans-Pecos Texas, and into southern New Mexico and northeastern
FRES32 Texas savanna
FRES33 Southwestern shrubsteppe
FRES35 Pinyon - juniper
NM TX MEXICO
BLM PHYSIOGRAPHIC REGIONS :
7 Lower Basin and Range
13 Rocky Mountain Piedmont
14 Great Plains
KUCHLER PLANT ASSOCIATIONS :
K059 Trans-Pecos shrub savanna
K086 Juniper - oak savanna
K087 Mesquite - oak savanna
SAF COVER TYPES :
66 Ashe juniper - redberry (Pinchot) juniper
239 Pinyon - juniper
SRM (RANGELAND) COVER TYPES :
HABITAT TYPES AND PLANT COMMUNITIES :
Mexican buckeye has not been listed as a dominant or indicator in
published classification schemes.
SPECIES: Ungnadia speciosa
WOOD PRODUCTS VALUE :
Wood of the Mexican buckeye is reddish-brown, soft, brittle, and close
grained . Sapwood is lighter in color . Plants can be cut back
regularly for firewood .
IMPORTANCE TO LIVESTOCK AND WILDLIFE :
Mexican buckeye is seldom browsed by domestic livestock except during
periods of food scarcity [6,23]. Fruit and leaves contain the toxic
alkaloid saponin which is poisonous to livestock . Mexican buckeye
may be responsible for occasional losses of cattle and goats in parts of
southern New Mexico .
Seeds are eaten by insects and some small mammals after they fall to the
Mexican buckeye browse is relatively unpalatable to domestic livestock.
The sweet-tasting seeds  are readily eaten by a variety of small
NUTRITIONAL VALUE :
Nutritional value of Mexican buckeye foliage has been documented as
(percentage composition - dry weight)
Protein Ether Crude N-free H2O Ash Potash Lime Magnesia Phosphoric
extract fiber extract acid
12.03 2.20 21.94 51.19 6.62 6.02 1.39 3.17 0.54 0.36
COVER VALUE :
Mexican buckeye presumably provides cover for a variety of wildlife
species. Trees may also produce shade for domestic livestock.
VALUE FOR REHABILITATION OF DISTURBED SITES :
OTHER USES AND VALUES :
Mexican buckeye can be planted as a shade tree or as an ornamental in
landscaping [6,20]. It is attractive when either planted alone or
intermixed with other species . Fragrant, showy flowers enhance its
attractiveness during the spring [19,23]. Mexican buckeye can be
trained as a hedge, planted onto berms of earth-covered homes, and used
as a "display thicket shrub" . Flowers provide nectar for honey
bees, and it is considered a good honey plant .
Children of west Texas reportedly use the round seeds of Mexican buckeye
as playing marbles . However, in view of its toxicity to rats in
laboratory studies, this use should probably be discouraged.
OTHER MANAGEMENT CONSIDERATIONS :
Toxicity: The sweet seeds of Mexican buckeye taste like pistachio nuts
and were formerly considered as a potential human food source .
Stanford  and his colleagues reportedly consumed up to 20 seeds
without suffering ill effects. However, results of laboratory tests
with rats soon put an end to these culinary experiments. Rats which had
ingested Mexican buckeye seeds soon exhibited numerous signs of both
neurological and organ damage and most died within 3 weeks . Seeds
can cause dizziness, nausea, and abdominal discomfort in humans [6,16].
Spider infestations: Fruit of Mexican buckeye is commonly infested with
spiders . Where infestations occur, seeds may be "glued" to the
capsules by web-building activities and commonly remain on the tree
until the following spring. On the average, approximately 10 percent of
all fruit is infested .
BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Ungnadia speciosa
GENERAL BOTANICAL CHARACTERISTICS :
Mexican buckeye grows as an upright or spreading, multistemmed shrub or
small tree [19,23]. It commonly reaches 4 to 15 feet (1.2-4.6 m) in
height but on favorable sites can grow to 30 feet (9.5 m) with trunk
diameters of 10 inches (25.4 cm) [6,19,23]. Bark is a mottled light
gray to brown, with shallow fissures developing on old trunks [16,23].
Slender brown to orange, pubescent twigs become reddish-brown and
glabrous with age . Some roots grow horizontally along the rock or
soil surface while others extend deep into the vertical face of soft
rock cliffs .
Leaves of Mexican buckeye are deciduous, alternate, and odd-pinnately
compound [17,18]. The three to seven ovate-lanceolate leaflets are
leathery with crenate-serrate margins [16,23]. The upper surface is
dark green and glabrous, whereas the lower surface is paler and
pubescent to glandular .
Small fragrant flowers are rose to purplish-pink and are borne in
clusters on bare stems [16,19,23]. Fruit is a woody, reddish-brown,
three-lobed pod or capsule 1 to 1.5 inches (2.5-3.8 cm) in diameter
[16,19]. The shiny, dark brown to black, rounded seeds average
approximately 0.4 to 0.6 inch (1-1.5 cm) in diameter . Seeds are
smooth, leathery and "buckeyelike" [17,19,23]. Each capsule generally
contains a single seed .
RAUNKIAER LIFE FORM :
Undisturbed State: Phanerophyte (nanophanerophyte)
Undisturbed State: Phanerophyte (microphanerophyte)
Undisturbed State: Phanerophyte (mesophanerophyte)
Burned or Clipped State: Chamaephyte
Burned or Clipped State: Hemicryptophyte
REGENERATION PROCESSES :
Mexican buckeye reproduces through seed or by vegetative means. However,
seedlings are rarely observed under natural conditions .
Seed: Mexican buckeye first flowers during the 3rd year when plants
have reached approximately 2 to 3.5 feet (0.6-1.1 m) in height .
Each plant produces an abundance of seed annually. Some seed falls from
the plant when fruit first ripens in the fall. However, some fruit may
persist on the tree through winter [19,22].
Seedlings grow well in full sun on warm, damp soil. Those grown in even
partial shade may appear stunted and eventually die. Conditions
necessary for seedling establishment, such as warm, but moist soil and
full sun, may be rare in the desert Southwest. Seedling establishment
generally occurs only in years with unusually abundant late summer and
early fall rainfall. During the course of an 8-year study, Stanford
 observed Mexican buckeye seedlings in only 1 year. Under optimum
greenhouse conditions, germination rates can exceed 95 percent .
Seedling emergence by planting date has been documented as follows :
date collected date of color 1st yr.
and planted emergence of seed development
6/14 8/2 green stunted
6/21 7/28 green stunted
6/28 7/22 green stunted
7/6 7/24 faint brn. patch stunted
7/13 7/28 dark brn. patch weak
7/20 8/3 mostly dark brn. good
7/27 8/9 fully brown good
8/3 8/18 fully brown good
8/10 8/22 fully brown good
8/17 8/30 fully brown good
8/24 9/9 fully brown good
8/31 9/18 fully brown good
Vegetative regeneration: Mexican buckeye coppices readily . Plants
cut to ground level at 4- or 5-year intervals retain good vigor and
SITE CHARACTERISTICS :
Mexican buckeye grows on lower mountain slopes and foothills, in
arroyos, and along streambanks in valley bottoms [6,16,23]. It commonly
occurs on the exposed face or rim of chalk caprock cliffs and along
fractures or depressions in igneous or limestone outcrops [5,19].
Mexican buckeye is tolerant of full sun and thrives under drought
conditions . It is commonly associated with deciduous riparian
woodlands, oak-juniper woodlands, and desert grassland communities
Plant associates: Common associates include Ashe juniper (Juniperus
ashei), netleaf hackberry (Celtis reticulata), live oak (Quercus
fusiformis), Lacey oak (Q. glaucoides), Texas persimmon (Diospyros
texana), black walnut (Juglans nigra), bumelia (Bumelia lanuginosa), and
black cherry (Prunus serotina) .
Soils: Mexican buckeye typically grows on well-drained calcareous
Elevation: In Trans-Pecos Texas, Mexican buckeye grows from 1,000 to
6,500 feet (305-1,981 m) in elevation .
SUCCESSIONAL STATUS :
Mexican buckeye grows in a number of riparian woodland communities.
These woodlands generally represent climax or "postclimax" communities
. Little is known about the successional role of Mexican buckeye in
oak-juniper woodlands or in desert grassland communities.
SEASONAL DEVELOPMENT :
Mexican buckeye flowers approximately 10 days after buds first appear
. In Trans-Pecos Texas, flowering occurs from March to June .
Leaves develop soon after the flowers . Fruit ripens in July 
or as late as August or October . Fruit turns dark brown in the fall
and unopened capsules may persist through the winter . Plants
become dormant within 2 weeks of the first frost or at leaf fall .
SPECIES: Ungnadia speciosa
FIRE ECOLOGY OR ADAPTATIONS :
Wright  notes that fires have historically been relatively
unimportant in the Chihuahuan Desert, which is dominated by shrubs
rather than grasses. Mexican buckeye often occurs in deciduous riparian
woodlands, which burn infrequently.
It is not known whether Mexican buckeye possesses specific adaptations
to fire. However, the majority of shrubs indigenous to southwestern
Texas sprout readily from the root crown after fire . Mexican
buckeye coppices from the root crown after mechanical removal , and
postfire sprouting is possible. Natural seedling establishment is
extremely rare , but limited seedling establishment from off-site
sources may occur in unusually moist years.
FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find Fire Regimes".
POSTFIRE REGENERATION STRATEGY :
survivor species; on-site surviving root crown or caudex
off-site colonizer; seed carried by animals or water; postfire yr 1&2
SPECIES: Ungnadia speciosa
IMMEDIATE FIRE EFFECT ON PLANT :
The effects of fire on Mexican buckeye have not been well documented.
Aboveground portions of the plant are presumably killed by fire.
However, postfire survival of the root crown is possible, if not likely.
DISCUSSION AND QUALIFICATION OF FIRE EFFECT :
PLANT RESPONSE TO FIRE :
The response of Mexican buckeye to fire is not well known. Plants
coppice readily after mechanical removal , and a similar response is
possible after fire. Establishment of some seed from off-site may occur
in years of unusually abundant summer and fall rainfall. However,
seedling establishment is extremely rare under ordinary conditions .
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE :
FIRE MANAGEMENT CONSIDERATIONS :
Bock and Bock  report that prescribed fire is "difficult to manage
and potentially very destructive" in established riparian woodlands of
the Southwest. These relatively rare and fragile areas provide
important food and cover for desert wildlife . Because browse and
cover are often limited in these areas, burning is not generally
References for species: Ungnadia speciosa
1. Van Auken, O. W.; Ford, A. L.; Stein, A.; Stein, A. G. 1980. Woody vegetation of upland plant communities in the southern Edwards Plateau. Texas Journal of Science. 32: 23-35. 
2. Bernard, Stephen R.; Brown, Kenneth F. 1977. Distribution of mammals, reptiles, and amphibians by BLM physiographic regions and A.W. Kuchler's associations for the eleven western states. Tech. Note 301. Denver, CO: U.S. Department of the Interior, Bureau of Land Management. 169 p. 
3. Bock, Carl E.; Bock, Jane H. 1990. Effects of fire on wildlife in southwestern lowland habitats. In: Krammes, J. S., technical coordinator. Effects of fire management of southwestern natural resources: Proceedings of the symposium; 1988 November 15-17; Tucson, AZ. Gen. Tech. Rep. RM-191. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 50-64. 
4. Cottle, H. J. 1931. Studies in the vegetation of southwestern Texas. Ecology. 12(1): 105-155. 
5. Carignan, Jeanette M. 1988. Ecological survey and elevational gradient implications of the flora and vertebrate fauna in the northern Del Norte Mountains, Brewster Co., Tx. Alpine, TX: Sul Ross State University. 181 p. Thesis. 
6. Dayton, William A. 1931. Important western browse plants. Misc. Publ. 101. Washington, DC: U.S. Department of Agriculture. 214 p. 
7. Dick-Peddie, W. A.; Moir, W. H. 1970. Vegetation of the Organ Mountains, New Mexico. Science Series No. 4. Fort Collins, CO: Colorado State University, Range Science Department. 28 p. 
8. Fraps, G. S.; Cory, V. L. 1940. Composition and utilization of range vegetation of Sutton and Edwards Counties. Bulletin No. 58. College Station, TX: Texas Agricultural Experiment Station. 39 p. 
9. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; [and others]. 1977. Vegetation and environmental features of forest and range ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of Agriculture, Forest Service. 68 p. 
10. Hanselka, C. Wayne, ed. 1980. Prescribed range burning in the coastal prairie and eastern Rio Grande Plains of Texas: Proceedings of a symposium; 1980 October 16; Kingsville, TX. College Station, TX: The Texas A&M University System, Texas Agricultural Extension Service: 128 p. 
11. Kartesz, John T.; Kartesz, Rosemarie. 1980. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. Volume II: The biota of North America. Chapel Hill, NC: The University of North Carolina Press; in confederation with Anne H. Lindsey and C. Richie Bell, North Carolina Botanical Garden. 500 p. 
12. Kuchler, A. W. 1964. Manual to accompany the map of potential vegetation of the conterminous United States. Special Publication No. 36. New York: American Geographical Society. 77 p. 
13. Little, Elbert L., Jr. 1976. Atlas of United States trees. Volume 3. Minor western hardwoods. Misc. Publ. 1314. Washington, DC: U.S. Department of Agriculture, Forest Service. 13 p. 290 maps. 
14. Little, Elbert L., Jr. 1979. Checklist of United States trees (native and naturalized). Agric. Handb. 541. Washington, DC: U.S. Department of Agriculture, Forest Service. 375 p. 
15. Lyon, L. Jack; Stickney, Peter F. 1976. Early vegetal succession following large northern Rocky Mountain wildfires. In: Proceedings, Tall Timbers fire ecology conference and Intermountain Fire Research Council fire and land management symposium; 1974 October 8-10; Missoula, MT. No. 14. Tallahassee, FL: Tall Timbers Research Station: 355-373. 
16. Powell, A. Michael. 1988. Trees & shrubs of Trans-Pecos Texas including Big Bend and Guadalupe Mountains National Parks. Big Bend National Park, TX: Big Bend Natural History Association. 536 p. 
17. Preston, Richard J., Jr. 1948. North American trees. Ames, IA: The Iowa State College Press. 371 p. 
18. Raunkiaer, C. 1934. The life forms of plants and statistical plant geography. Oxford: Clarendon Press. 632 p. 
19. Stanford, Geoffrey. 1981. Ungnadia speciosa (Mexican buckeye). Plant Propagator. 28(2): 5-6. 
20. Steger, Robert E.; Beck, Reldon F. 1973. Range plants as ornamentals. Journal of Range Management. 26: 72-74. 
21. U.S. Department of Agriculture, Soil Conservation Service. 1982. National list of scientific plant names. Vol. 1. List of plant names. SCS-TP-159. Washington, DC. 416 p. 
22. Van Dersal, William R. 1938. Native woody plants of the United States, their erosion-control and wildlife values. Washington, DC: U.S. Department of Agriculture. 362 p. 
23. Vines, Robert A. 1960. Trees, shrubs, and woody vines of the Southwest. Austin, TX: University of Texas Press. 1104 p. 
24. Wright, Henry A. 1972. Shrub response to fire. In: McKell, Cyrus M.; Blaisdell, James P.; Goodin, Joe R., eds. Wildland shrubs--their biology and utilization: Proceedings of a symposium; 1971 July; Logan, UT. Gen. Tech. Rep. INT-1. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station: 204-217. 
25. Severson, Kieth E.; Rinne, John N. 1990. Increasing habitat diversity in Southwestern forests and woodlands via prescribed fire. In: Krammes, J. S., technical coordinator. Effects of fire management of southwestern natural resources: Proceedings of the symposium; 1988 November 15-17; Tucson, AZ. Gen. Tech. Rep. RM-191. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 94-104. 
26. Stickney, Peter F. 1989. Seral origin of species originating in northern Rocky Mountain forests. Unpublished draft on file at: U.S. Department of Agriculture, Forest Service, Intermountain Research Station, Fire Sciences Laboratory, Missoula, MT; RWU 4403 files. 10 p. 
27. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. 
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