Aesculus californica, California buckeye
Howard, Janet L. 1992. Aesculus californica, California buckeye. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-reviews/aescal
| Abbreviation | Common Name | Scientific Name | Classification | Status |
|---|---|---|---|---|
| Plants | ||||
| AESCAL | California buckeye | Aesculus californica | Life Form: Plants/Shrub, Plants/Tree Kingdom: Plantae Class: Dicot Order: Sapindales Family: Hippocastanaceae Genus: Aesculus | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
Taxonomy
The currently accepted scientific name of California buckeye is Aesculus californica (Spach) Nutt. [18,21]. There are no recognized subspecies, varieties, or forms.
Synonyms
- Calothyrsus californica
Other Common Names
buckeye, horsechestnut
General Distribution
California buckeye is endemic to California. It occurs in the Klamath and Coast Ranges from Siskiyou County south to Los Angeles County. In the Cascade Range and the foothills of the Sierra Nevada, it occurs from Shasta County south to Kern County. California buckeye is occasionally found in the Central Valley in Yolo, Colusa, and Stanislaus Counties [5].
States and Provinces
- United States: CA
Site Characteristics
California buckeye grows on dry slopes, in canyons, and along waterways [5,21]. In the Central Valley it occurs along stream and river banks [5,19]. It is associated with poison-oak (Toxicodendron diversilobum) in most communities in which it occurs [5,17].
Soil: California buckeye grows in sandy, sandy-loam, or gravelly-loam soils [5].
Climate: California buckeye occurs in a Mediterranean climate with cool moist winters and hot dry summers [5,15,18]. The mean annual rainfall is less than 14 inches, and temperatures are in excess of 100 degrees Fahrenheit (38 degrees C) for several successive days every summer [14].
Elevation: California buckeye occurs below 4,000 feet (1,219 m) [21].
Plant Communities
California buckeye woodland is recognized as a distinct plant community [13]. The species may also codominate oak (Quercus spp.) woodland. Interior live oak (Q. wislizenii) and blue oak (Q. douglasii) are the most common codominants of oak woodland [1,2,3,22,23]. In chaparral, it is sometimes a dominant shrub or tree [2,4]. The following published classification schemes list California buckeye as a climax species or a dominant part of the vegetation in community types or plant associations:
| Area | Classification | Authority |
|---|---|---|
| California: Coast Ranges with foothills | mixed oak community types | Allen & others 1991 |
| California: Sierra Nevada | foothill woodland plant associations | Thorne 1976 |
| California: Klamath Mountains | northern mixed chaparral plant associations | Holland 1986 |
| California: Pinnacles National Monument | CA buckeye woodland community types | Halverson & Clark 1986 |
Botanical Description
California buckeye in bloom.
California buckeye is a large shrub or tree up to 23 feet (7 m) tall. The 2-to 6-inch-long (5-15 cm) leaves are deciduous and palmately compound [21]. Flowers are borne on a terminal panicle 4 to 8 inches (10-20 cm) long. The pear-shaped, light brown fruit contains one to six glossy brown seeds 0.8 to 1.2 inches (2-3 cm) in diameter [5,21].
Raunkiaer Life Form (Raunkiaer 1934)
- Phaneropyte
Seasonal Development
California buckeye flowers from April to September [24]. New leaves emerge from March to June while soil moisture is abundant [20]. The leaves dry up and are shed in late spring or early summer in Sierra Nevada foothill populations but may be retained through fall in coastal populations when soil moisture remains available [5]. Fruits ripen from September to October and are dropped from November to December [24].
Regeneration Processes
California buckeye seeds.
Sexual: California buckeye reproduces by seed [5]. The average tree produces approximately 100 seeds per year. Seed dispersal is poor and is accomplished mainly by gravity or water; dispersal by animals is rare [13]. Seeds are viable for only 1 year and are shed from November to mid-February [24]. Germination occurs within several weeks of shedding if the soil temperature is above 40 degrees Fahrenheit (4 degrees C). If the temperature persists below 40 degrees for 2 months or more the seeds are susceptible to fungal infections or desiccation [12]. Germination success rates of 75 percent have been reported under laboratory conditions [19].
Asexual: California buckeye can sprout from the stump or root crown [3,28].
Successional Status
California buckeye exhibits both tolerant and intolerant characteristics. It occurs as widely scattered individuals in open grasslands. It also occurs as an understory shrub in mixed evergreen forest [3]. It is a climax indicator in chaparral and mixed oak communities [1] and in California buckeye woodlands [8].
Immediate Fire Effects
Fire top-kills California buckeye [25].
Postfire Regeneration Strategy (Stickney 1989)
- survivor species; on-site surviving root crown
- off-site colonizer; seed carried by water; postfire year 1 & 2
- secondary colonizer; off-site seed carried to site after year 2
Fire Adaptations
Plant adaptations: California buckeye sprouts from the root crown after top-kill by fire [5,28]. Seeds would probably not survive fire because they are highly susceptible to desiccation by heat [8]. Seed is often transported by water and could be carried to a burn site in that manner [13].
Fire ecology: Early leaf fall results in accumulation of dry litter around the plant early in the fire season.
Plant Response to Fire
Information regarding California buckeye's response to fire is limited. Sampson [25] has said that sprouting chaparral brush species, including California buckeye, recover rapidly following a fire, sending out new shoots during the first growing season. Growth in subsequent seasons is also rapid, with the plant sometimes exceeding its prefire mass within a few years. Sprouting can occur within a few weeks following fire, even in the summer months. Growth is supported by drawing on food and water reserves in the fully developed root system [20].
See this Fire Study in FEIS for further information on responses of California buckeye and other chaparral and woodland species to fire:
- Damage and recovery in southern Sierra Nevada foothill oak woodland after a severe ground fire (blue oak-interior live oak/annual grass community)
Fire Regimes
For fire regime information, search FEIS for this species by entering the species name or acronym on the home page and selecting “Fire Regime” as the publication type.
Fire Management Considerations
Grazing considerations: California buckeye cannot be successfully eliminated by occasional prescribed burning. Fire may control it if the area is reburned every 7 to 8 years and immediately reseeded with herbaceous vegetation [14]. Otherwise, California buckeye will recover at the expense of other plant species, including desirable herbs [14,25].
Federal Status
None
Other Status
No entry.
Importance to Wildlife and Livestock
California buckeye is toxic to all classes of livestock and wildlife. The bark, leaves, stems, fruits, and seeds all contain glycosidal compounds which cause haemolytic action on red blood cells and depress the central nervous system when ingested. This species has been implicated in inducing abortion in cattle [5,18].
Palatability and Nutritional Value
Despite its toxicity, California buckeye flowers, leaves, and shoots are palatable to livestock and wildlife. Hedrick [14] has listed it among the 20 chaparral browse plants most preferred by cattle and black-tailed deer. The palatability of the seeds for black-tailed deer, rodents, and Steller's jay is fair to poor [5].
The dry matter composition of California buckeye seeds is 80 percent carbohydrate, 5 percent protein, 1 percent fat, 2 percent ash, 3 percent fiber, and 9 percent miscellaneous [12]. Protein content of the leaves and stems varies from 31 percent in April to 5 percent in October [6]. Carbohydrate content of leaves and stems varies from 50 percent in April to 1 percent in October [20]. Since California buckeye is a systemic poison, how much of this nutrition is actually metabolized by seed-eating or browsing livestock and wildlife in unknown. (see Importance to Wildlife and Livestock).
Cover Value
The cover value of California buckeye is poor from late spring through late winter due to early leaf fall.
Value for Rehabilitation or Restoration of Disturbed Sites
California buckeye is valuable as a soil binder on stream or river banks and on steep slopes [11,17,26]. Seed can be obtained by harvesting native plants. Seed propagation methods have been detailed [20,24].
Other Uses
California buckeye is used as a landscaping ornamental [24].
The seeds of California buckeye served as a staple for California Indians, who would mash the roasted seeds and then leach them to remove the poison [5]. Native Americans also secured the seeds in streams and other waterways in order to stupefy fish for easy capture [21].
California buckeye is occasionally used for lumber and paper pulp [25].
Other Management Considerations
Grazing: California buckeye often considered undesirable on rangeland because of its toxicity.
Apian considerations: Honeybees are the chief pollinators of California buckeye, but the pollen and nectar are toxic to them [5,9,14]. Losses of adult honeybees and their larvae due to poisoning can be severe [9]. Human beings have been poisoned by eating honey made from California buckeye [18].
Control treatments: California buckeye is susceptible to spray or injection/cut surface treatments of phenoxy herbicides and picloram [7,14,27]. Hand or mechanical brush control is ineffective unless the root crown is removed [25,28].
Table A1— Forest and range ecosystems, Bureau of Land Management (BLM) physiographic regions, Kuchler plant associations, Society for American Foresters (SAF) forest cover types, and Society for Rangeland Management (SRM) rangeland cover types in which this species occurs.
Forest and Range Ecosystems (Garrison et al. 1977)
- FRES20 Douglas-fir
- FRES21 Ponderosa pine
- FRES27 Redwood
- FRES28 Western hardwoods
- FRES34 Chaparral - mountain shrub
BLM Physiographic Regions (Bernard and Brown 1977)
- 3 Southern Pacific Border
- 4 Sierra Mountains
- 7 Lower Basin and Range
Kuchler Plant Associations (Kuchler 1964)
- K003 Silver fir - Douglas-fir forest
- K005 Mixed conifer forest
- K006 Redwood forest
- K009 Pine - cypress forest
- K010 Ponderosa shrub forest
- K029 California mixed evergreen forest
- K030 California oakwoods
- K033 Chaparral
- K034 Montane chaparral
SAF Cover Types (Eyre 1980)
- 229 Pacific Douglas-fir
- 231 Port-Orford-cedar
- 232 Redwood
- 234 Douglas-fir - tanoak - Pacific madrone
- 243 Sierra Nevada mixed conifer
- 244 Pacific ponderosa pine - Douglas-fir
- 245 Pacific ponderosa pine
- 246 California black oak
- 247 Jeffrey pine
- 248 Knobcone pine
- 249 Canyon live oak
- 250 Blue oak - gray pine
- 255 California coast live oak
SRM Rangeland Cover Types (Shiflet 1994)
- No entry.
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