General: Buckeye Family (Hippocastanaceae). This native, deciduous shrub or tree reaches 12 m in height with a broad, rounded crown. The palmately compound leaves occur in leaflets of 5 to 7 and each leaflet is oblong-lanceolate and finely serrate. The inflorescence has many showy flowers in a panicle-like arrangement and it is erect, 1-2 dm. in length. Each individual flower has 4-5 petals and these are white to pale rose with 5-7 exserted stamens. The fruit is pear-shaped and smooth. The large, shiny light-brown seeds are 2-5 cm.
Horse chesnut; Indian names: de-sa' ka-la' (Pomo); far'-sokt (Nomlaki); sympt'-ol (Yuki); ah'-te (Coast Miwok)
Regularity: Regularly occurring
Klamath and Coast Ranges from Siskiyou County County south to Los
Angeles County. In the Cascade Range and the foothills of the Sierra
Nevada, it occurs from from Shasta County south to Kern County.
California buckeye is occasionally found in the Central Valley in Yolo,
Colusa, and Stanislaus Counties .
Regional Distribution in the Western United States
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
3 Southern Pacific Border
4 Sierra Mountains
7 Lower Basin and Range
Occurrence in North America
A. californica occurs below 1200 m in elvation within the the Klamath and Coast Ranges from Siskiyou County south to Los Angeles County, and in the Cascade Range and the foothills of the Sierra Nevada, it is found from from Shasta County south to Kern County. Less commonly it occurs in the Central Valley in Colusa, Yolo and Stanislaus Counties. California Buckeye is found in the following diverse vegetative associations: chaparral, montane chaparral, California mixed oak forest, California mixed evergreen forest, Ponderosa shrub forest, cypress forest, redwood forest, mixed conifer forest and silver fir/douglas fir forest. A. californica primarily occurs on sandy, sandy-loam, or gravelly-loam soils.
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 . 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].
Key Plant Community Associations
California buckeye woodland is recognized as a distinct plant community
. 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
(cts) or plant associations (pas):
Area Classification Authority
CA: Coast Ranges mixed oak cts Allen & others 1991
Sierra Nevada foothill woodland pas Thorne 1976
Klamath Mts. northern mixed Holland 1986
Monument Ca buckeye woodland cts Halverson & Clark
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
More info for the term: shrub
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
K034 Montane chaparral
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES21 Ponderosa pine
FRES28 Western hardwoods
FRES34 Chaparral - mountain shrub
[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
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 .
Elevation: California buckeye occurs below 4,000 feet (1,219 m) .
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
229 Pacific Douglas-fir
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 - Digger pine
255 California coast live oak
Adaptation: The California buckeye is one of the first shrubs to leaf out in spring and one of the earliest to shed its leaves in mid-summer. It is found on dry slopes, canyons and the borders of streams in many plant communities below 1700 m. in northwestern and central western California, Cascade Range, Sierra Nevada foothills, Tehachapi Mountains, Great Central Valley, and southwestern Mohave Desert.
General: Harvest the large seeds from the tree or shrub about November. Plant them in the ground immediately--half buried in an area of full sun or light shade. There is a light spot on the seed, which is the growing point when being formed. The radicle will sprout from this area so make sure that this spot is covered with soil. Plant the seeds in a well-drained soil. Water the soil immediately after planting, and if there is not enough rain during the rainy season, supplement it with hand watering. The plants will also need some summer watering the first year so a good rule to follow is to keep the soil damp. The tree is a fast grower and can achieve as much as ten inches in height in one year. After buckeye seeds have been in the ground one full year, they should become established, and will not need continual care.
Fire Management Considerations
eliminated by prescribed burning. Fire will bring it under control if
the area is reburned every 7 to 8 years and immediately reseeded with
herbaceous vegetation . Otherwise, California buckeye will recover
at the expense of more desirable herbaceous plants [14,25].
Immediate Effect of Fire
survivor species; on-site surviving root crown or caudex
off-site colonizer; seed carried by animals or water; postfire yr 1&2
secondary colonizer; off-site seed carried to site after year 2
Plant adaptations: California buckeye sprouts from the root crown after
aboveground portions of the plant have been damaged [5,28]. Seeds would
probably not survive fire because they are highly susceptible to
desiccation by heat . Seed is often transported by water and could
be carried to a burn site in that manner .
Fire ecology: Early leaf fall results in accumulation of dry litter
around the plant early in the fire season.
More info for the terms: climax, shrub
California buckeye exhibits both tolerant and intolerant
characteristics. It occurs as a widely scattered individuals in open
grasslands. It also occurs as an understory shrub in mixed evergreen
forest . It is a climax indicator in chaparral and mixed oak
communities  and in California buckeye woodlands .
produces approximately 100 seeds per year. Seed dispersal is poor and
is accomplished mainly by gravity or water; dispersal by animals is rare
. Seeds are viable for only 1 year and are shed from November to
mid-February . 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 .
Germination success rates of 75 percent have been reported under
laboratory conditions .
Asexual: California buckeye can sprout from the stump or root crown
Growth Form (according to Raunkiær Life-form classification)
Plant Response to Fire
Sampson  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 .
Life History and Behavior
California buckeye flowers from April to September . New leaves
emerge from March to June while soil moisture is abundant . 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 . Fruits ripen from
September to October and are dropped from November to December .
Molecular Biology and Genetics
Barcode data: Aesculus californica
Statistics of barcoding coverage: Aesculus californica
Public Records: 5
Specimens with Barcodes: 5
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNR - Unranked
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).
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 .
Human beings have been poisoned by eating honey made from California
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].
Cultivars, improved and selected materials (and area of origin)
These plant materials are readily available from commercial sources.
When the shrub is mature, dead and dying branches can be lightly pruned if necessary.
Relevance to Humans and Ecosystems
The cover value of California buckeye is poor from late spring through
late winter due to early leaf fall.
Other uses and values
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 . Native Americans also secured the seeds in streams and
other waterways in order to stupefy fish for easy capture .
Value for rehabilitation of disturbed sites
and on steep slopes [11,17,26]. Seed can be obtained by harvesting
native plants. Seed propagation methods have been detailed [20,24].
Importance to 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].
carbohydrate, 5 percent protein, 1 percent fat, 2 percent ash, 3 percent
fiber, and 9 percent miscellaneous . Protein content of the leaves
and stems varies from 31 percent in April to 5 percent in October .
Carbohydrate content of leaves and stems varies from 50 percent in April
to 1 percent in October . 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 Livestock and Wildlife).
palatable to livestock and wildlife. Hedrick  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
Stellar's jay is fair to poor .
Wood Products Value
Ethnobotanic: This tree had multiple cultural uses among California Indian tribes. Many indigenous groups utilized buckeye seeds for food, often when other plant food sources were scarce. These tribes included the Costanoan, Salinan, Kitanemuk, Serrano, Wappo, Sierra Miwok, Coast Miwok, Chumash, Kawaiisu, Northern Maidu among others. The Pomo ate the seeds even when other important food plants were plentiful. The seeds are poisonous to humans in the raw state. Thus, the nuts were cracked open with a rock, the shells removed, the seeds pounded into flour, and their toxic saponins removed in a lengthy leaching process. The meal was subsequently cooked and eaten. There are many different methods for processing and cooking buckeye seeds for food, depending upon the tribe. The seeds have medicinal properties and were cut into pieces, mixed with water, and made into suppositories for hemorrhoids by the Costanoan and Kawaiisu. The Pomo cut bark from the base of the tree and made a poultice, which was laid on a snakebite. Young buckeye shoots were sometimes used as spindles or twirling sticks in fire-making kits of the Sierra Miwok, Northern Maidu, Wappo, Yahi and other tribes. Many tribes mashed buckeye nuts and poured the contents into quiet pools to stupefy or kill fish.
Wildlife: Do not plant buckeyes near apiaries as the flowers are poisonous to honey bees. No wildlife eat buckeye seeds except squirrels, such as the California ground squirrel (Citellus beecheyi).
It is a large shrub or small tree, up to 4–12 m (13–39 ft) tall, with gray bark often coated with lichens and mosses. It typically is multi-trunked, with a crown as broad as it is high. Trees are long lived, with an estimated lifespan between 250-280 (300 maximum) years. The leaves are dark green, palmately compound with five (rarely seven) leaflets. Each leaflet is 6–17 cm (2.4–6.7 in) long, with a finely toothed margin and (particularly in spring) downy surfaces. The leaves are tender and prone to damage from both spring freezing or snow and summer heat and desiccation.
The flowers are sweet-scented, white to pale pink, borne on erect panicles 15–20 cm (6–8 in) long and 5–8 cm (2–3 in) broad. The fruit is a fig-shaped capsule 5–8 cm (2–3 in) long, containing a large (2–5 cm (0.8–2.0 in)), round, orange-brown seed; the seeds are poisonous.
A. californica has adapted to its native Mediterranean climate by growing during the wet late winter and spring months and entering dormancy in the dry summer months, though those growing in coastal regions tend to hold on to their leaves until mid-autumn.
Distribution and habitat
A. californica is widely distributed in California, growing along the central coast and in the lower elevations of the Sierra Nevada and Cascade Range. Its range extends to the foothills of the Siskiyou Mountains in the Rogue Valley in Oregon.
It is found growing in a wide range of conditions from crowded, moist, semi-shaded canyon bottoms to dry south-facing slopes and hilltops. In the coastal ranges north of Big Sur it is found growing alone on slopes, or intermingled with valley oak (Quercus lobata), Oregon oak (Q. garryana), coast live oak (Q. agrifolia) and California bay laurel (Umbellularia californica). In the foothills of the Sierra Nevada, A. californica can be found standing alone in grassland at the lowest elevations, intermingled in blue oak woodlands at intermediate elevations, and in mixed evergreen forests of black oak (Q. kelloggii), gray pine (Pinus sabiniana), ponderosa pine (P. ponderosa) and interior live oak (Q. wislizeni) as it nears the limit of its range.
Toxicity and uses
Local native American tribes, including the Pomo, Yokut, and Luiseño, used the poisonous nuts to stupefy schools of fish in small streams to make them easier to catch. The bark, leaves, and fruits contain the neurotoxic glycoside aesculin, which causes hemolysis of red blood cells. Buckeye also makes a good fireboard for bowdrill or hand drill.
Native groups occasionally used the nuts as a food supply when the acorn supply was sparse; after boiling and leaching the toxin out of the nut meats for several days, they could be ground into a meal similar to that made from acorns. The nectar of the flowers is toxic to the Asian/European honeybee, so the trees should not be planted near apiaries. When the shoots are small and leaves are new, they are lower in toxins and are grazed by livestock and wildlife. The flowers are a rich nectar source for many species of butterflies.
It is used as an ornamental plant for its striking leaf buds, lime green foliage, fragrant white flowers, red-brown foliage in mid to late summer, and architectural silver branches through fall.
The tree acts as a soil binder, which prevents erosion in hilly regions.
- Elna S. Bakker (1984). An island called California: an ecological introduction to its natural communities. University of California Press. p. 74. ISBN 978-0-520-04948-2. Retrieved 2011-06-11.
- Philip Alexander Munz, David D. Keck (1973). A California Flora. University of California Press. p. 994. ISBN 978-0-520-02405-2. Retrieved 2011-06-20.
- Kat Anderson, Wayne Roderick. California Buckeye, in the USDA NRCS Plant Guide (Report). USDA. Retrieved 2011-06-20.
- Howard, Janet L. Aesculus californica, in the USDA Forest Service Fire Effects Information System (Report). USDA Rocky Mountain Research Station, Fire Sciences Laboratory. Retrieved 2011-11-07.
- Kevin Hintsa. Watching Butterflies on Mount Diablo (Report). Retrieved 2011-11-07.
- Callahan F. 2005 Kalmiopsis Journal, Vol. 12, 2005 Plant of the Year, California Buckeye (Aesculus californica (Spach.) Nutt.) Native Plant Society of Oregon ISSN 1055-419X. (.pdf)
- Casebeer, M. (2004). Discover California Shrubs. Sonora, California: Hooker Press. ISBN 0-9665463-1-8.
- Bakker, E. (1971). An Island Called California. Berkeley, California: University of California Press. ISBN 0-520-04948-9.
Names and Taxonomy
californica (Spach) Nutt. [18,21]. There are no recognized subspecies,
varieties, or forms.
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