California Buckeye
Aesculus californica
The California buckeye is a short, multi-trunked tree, growing only 4-12 meters tall. The stout trunks and numerous branches are knotted, with warty protrusions. The smooth, slightly scaled bark is a pale gray bark and is often coated in lichens and mosses. The wide, rounded crown, typically as broad as the trunk is tall, is populated by dark green leaves, though only for a short time. The palmate leaves are composed of 5 thin, soft leaflets with very finely toothed margins. Each delicate leaflet is 6-17 cm long and 2-5 cm wide. The small four-petalled flowers, white to pale pink in color, are borne on direct panicles — long stems surrounded by dense clusters of flowers. The panicles are 15-20 cm long and 5-8 cm wide. The leathery, pale brown fig-shaped seed capsule houses a single large, shiny brown seed, which can be glimpsed when the capsule splits in two.
Basic Information
Member of the Sapindaceae (Soapberry) family
Deciduous
Long-lived, with an average lifespan of 250-280 years, though some specimen can live over 300 years
Habitat
Native to California and southwestern Oregon, up to the foothills of the Siskiyou Mountains
In California, this plant is widespread, growing along the central coast and foothills of the Sierra Nevada and Cascade Ranges
Only Aesculus variety native to the western United States
Commonly found growing on the slopes and in the canyons of foothill woodlands, mixed evergreen forests, coastal sage scrub, and riparian areas
Ecological Role
Only wildlife known to eat the toxic fruit are ground squirrels
Flowers are a source of nectar and pollen for hummingbirds and insects, including bees and many butterfly species
especially valuable to migrating butterflies in late spring
Toxic to non-native honey bees, which become paralyzed and die
Pollen consumed by the queen may result in deformed offspring and decreased or halted egg production, which ultimately destroys the colony
Host to Phytophthora ramorum, a fungal pathogen that causes Sudden Oak Death (SOD)
Adapted to survive fires and drought
Loses leaves very early (in the late spring/early summer) to conserve water
One of the first trees to regrow leaves when winter rains return
Deep taproot helps it survive dry summers and drought
If destroyed by fire, the tree will re-sprout from the root crown
Reproduction
Blooms from April-June
Polygamo-monoecious — bears unisexual (separate male and female flowers) and bisexual flowers on the same plant
Most flowers on the panicles are male
Can be identified by exerted (extending beyond petals), orange-colored stamens (the pollen-producing structure)
Only a few flowers at the tip of the panicle are female
The seed matures on the tree through the summer and into early fall when the capsule withers and it’s released
Dispersed by gravity (rolling down hills), water (carried downstream), and squirrels
Germination occurs within a few weeks of the fruit’s fall, as the seed does not survive desiccation
Alternative Names
California Horse Chestnut, Shrub California Buckeye
Historical Uses
The California Buckeye was used extensively by California Native Americans
The bark was used to treat toothaches and snake bites
The fruit was applied as a salve for hemorrhoids
Wood made into bowls, bows, and drill sticks, which were used to make fire
Fruit used for food when acorns were scarce
Water must be run through mashed nuts over a few days to leach out the toxin and make it edible
The roots and nut were used for fishing
The crushed roots and but were thrown in slow-moving creeks or pools to stun the fish
The saponins and neurotoxin in the plant prevent fish from properly oxygenating
Fruits of the common snowberry (Symphoricarpos albus), the roots of California manroot (Marah fabacea), and the bulbs of soap plant (Chlorogalum pomeridianum) were similarly used
Additional Information
Has the largest seed of any native California plant and of any non-tropical plant species
The bark, leaves, and fruit all contain the neurotoxin glycoside aesculin
Buckeyes are a very old lineage of trees, surviving from the Paleocene period, just after the time of the dinosaurs
Their range has constricted since then, but they have adapted to the drier, hotter climate
