California Buckeye – Aesculus californica


In June of 2015, I visited Cambridge University Botanic Garden for the first time. CUBG is a beautiful and well-tended garden which holds, among other things, nine National Plant Collections. A National Plant Collection is a group of species and cultivated varieties (cultivars) that are of great historical, horticultural, or reference value in the UK.

Amongst all the interesting and unusual plants which were new to me, I was delighted to run into a friend who I knew very well from back home in California – the California Buckeye.


In the words of John Thomas Howell, author of Marin Flora, the California Buckeye is a sight to behold in all seasons, “…whether it is the tracery of bare branches etched against the winter sky, or the vernal opulence of leaf and flower conformed into a huge bouquet, or the dull rich tone of colored foliage bronzing the autumnal countryside.”

It was in my childhood that my father introduced me to hiking at night. I vividly remember how loud my footsteps fell on the dry ground, the dust rising to meld with the cool air. How the trees seemed so close, and how the stars sparkled coldly from their distant heights. On one particular night in my teens, when the gibbous moon was nearing its height, something bright caught my eye as I rounded the curve of a switchback trail on a steep hillside. There, in a clearing, shining luminously silver-white, was the bare form of a buckeye. It was high summer, nearing autumn, and the leaves were already shed from drought. Its naked skeleton, like a sinuous candelabra, seemed aflame with starlight. It was all the more vivid against its backdrop, for behind it stood a swathe of Douglas firs (Pseudotsuga menziesii), their green needles turned monochrome grey in the pale light.

That image is one of many that I associate with the California buckeye, but it is perhaps the one most vividly and searingly impressed upon me. For some time I stood there without moving, alone, having forgotten myself entirely as I became simply a pair of eyes swimming in a beautiful vision.

I recall also a great and old specimen in my father’s back garden which fell in a winter storm. As I was perhaps seven or eight years old at the time, the fallen branches seemed to me as a whole forest. I spent many wonder-filled hours threading through them, swinging from the satiny bark of the horizontal branches and hiding beneath the glossy green leaves. The following year, the jagged stump was overcrowded with new shoots, each racing its fellows to become the new leader.

I remember the fruits on a particular drizzly afternoon, their strange grey flesh turned slick by the rain, causing them to release their precious cargo with almost violent speed. The silky-smooth seed casings gleamed a gorgeous chestnut-brown like the irises of a deer. Those already on the ground, having ripened sooner, were putting forth their first roots, the radicles, which emerged smoothly from their shells to plunge into the ground like pale pink snakes. Their first leaves are as a delicate, living lace.

And oh, the flowers! When they bloom, that sweet scent pervades all the air, making one feel light-headed at the glory of spring. The panicles of flowers come alive with bees, and the tiny flowers are a soft shade of pastel yellow at the center, sometimes flushed with pink, fading into glistening white at the outermost margins.


Though typically a small tree of only 10-15 feet, specimens occasionally reach 40-60 feet in height.


Introduced to the UK in 1850.

Literary Use

Though there are many mentions of this species in books and poems, I would encourage anyone who likes poetry to read the poem ‘Buckeye As You Are’ by the Pulitzer Prize nominated poet Wendy Rose, which can be found here.

Pests and Diseases

Unlike horse chestnuts (Aesculus hippocastanum), the California buckeye (A. californica) is not targeted by the horse chestnut leaf miner (Cameraria ohridella).


California buckeye fruit is not edible raw because it contains a poisonous chemical compound, in this case a glycoside, known as aesculin.

Symptoms of aesculin poisoning include:

  • Circulatory disturbance(s)
  • Restlessness
  • Loss of bladder control (urinary incontinence)
  • Dilated pupils
  • Loss of coordination
  • Weakness
  • Involuntary muscular spasms or twitching
  • Paralysis
  • Stupor
  • (Rarely) death

Some Native American groups crushed the seeds to use as fish poison (see ‘Other Uses’ below).

The nectar and pollen are both toxic to honeybees, though this does not seem to deter bees from visiting the flowers to collect them.

Food Uses

As mentioned in the ‘toxicity’ subheading above, no part of the seed is edible raw. However, there are a number of ways to process buckeye seeds to make them edible.

For the Miwok, Modesse, Achomawi, and Esselen groups, California Buckeye seeds seem to have been less desirable than acorns, probably because they require significantly more leaching than acorns do. Rather than being a staple, buckeye fruits were more often used as a fallback during times when other foods were scarce.

Despite the extra leaching required, however, some groups, such as the Yana, used buckeye nuts as a staple. Buckeye nuts were widely eaten by many groups across California, including (but by no means limited to) the:

  • Atsugewi
  • Bear River
  • Huchnom
  • Kawaiisu
  • Kitanemuk
  • Maidu
  • Mendocino Indian
  • Nomlaki
  • Patwin
  • Sinkyone
  • Tubatulabal
  • Wappo
  • Yuki

Leaching Process

The leaching process seems to have varied somewhat between groups. Below are descriptions of some different processes.

Hot and Cold Leaching

The Nomlaki were known to leach buckeye nuts the same way they leached acorns:

  • Buckeye nuts were pounded
  • After mashing, they were leached, first with hot, and then with cold water
  • While the women were preparing buckeyes, as with fire making, no one was allowed to whistle, and they all had to remain very quiet (presumably because the process required concentration).
  • Once sufficiently leached, the mashed nuts were removed from the water and the sand rinsed off them
  • After rinsing, the pulp was formed into white balls and was either eaten in that form or stirred into a basket of water and drunk.

Leaching and Cooking

Use by an unspecified group:

  • Buckeye nuts were broken open and then immersed in water, where they were left to soak for a day.
  • After soaking, the nuts were drained and pounded into meal.
  • The meal was leached in a sand filter for a day.
  • The meal was thoroughly drained, which could take as much as day.
  • The process of leaching and draining was repeated up to ten times. To keep track of the number of times the operation had been carried out, sticks were placed to one side each time the draining was completed.
  • Once the nuts had been sufficiently leached, they were typically cooked and eaten immediately.

Blanching and Leaching

Use by the Kashaya Pomo:

  • Nuts were boiled whole, to loosen the shells
  • Shells removed
  • Nutmeats put back into boiling water until ‘soft like cooked potatoes’
  • Cooked nutmeats mashed between grinding stones
  • Mashed nutmeats either soaked and then strained, or strained without prior soaking
  • Mashed nutmeats soaked and leached for a ‘long time’, then eaten

Soaking and Leaching

The Kawaiisu First soaked and leached the nuts, then cooked them afterwards:

  • Nuts gathered after having fallen from the tree (typically sometime in November)
  • Seeds broken into pieces
  • Broken seeds soaked in water for two days
  • Seeds crumbled
  • Seeds leached (time spent leaching unspecified)
  • Crumbled, leached seeds boiled into mush

Leaching Without Cooking

The Atsugewi often leached buckeye nuts in cold water and then ate them without cooking them.

  • Nuts were first shelled
  • Mashed
  • Soaked ‘until the juice was gone’
  • The pap was then squeezed dry by hand, and often eat just like that, without further preparation or cooking

Roasting and Leaching

Some groups, such as the Round Valley Indians, roasted the nuts first, then leached them afterwards.

  • A hole was dug, lined with stones, and then the stones lined with willow (Salix) leaves.
  • Buckeye nuts were then placed in the hole and covered with a mixture of dirt and hot coals, then left to cook for as much as ten hours.
  • Once the cooking was complete, the nuts were first shelled, then either mashed or sliced, and finally leached in running water for a number of days.

The Nomlaki had an interesting technique:

  • Nuts were roasted and shelled (but left whole)
  • Roasted, shelled nuts were then immersed in running water (typically a stream) to leach for two or three weeks
  • Once leached, the nuts were crushed either with a block of wood or with one’s feet
  • The mashed pulp was strained through a willow (Salix) colander
  • The mashed, strained nuts were either eaten dry or made into soup
    • The soup allegedly looked like flour paste and had a gummy texture but a ‘cooling taste’
  • According to Jones, “There is one woman who knows the matter of buckeyes; not any woman can make it — not as with acorn soup.”

An old method used by the Kashaya Pomo:

  • Nuts were shelled and the meats roasted in hot coals until soft
  • Roasted nutmeats crushed and put into a sandy ‘leaching basin’ by running water
  • Mashed nutmeats leached for about five hours with stream water
  • When no longer bitter, the nutmeats could be eaten without further preparation.

Southwestern Pomo used a slightly different process than the Kashaya Pomo.

  • Nuts were collected when they had fallen from the trees
  • Roasted in hot ashes
  • Shelled
  • Crushed
  • Pulverized roasted nuts were then set into a sandy basin beside running water and rinsed for five hours
  • Once washed, the mashed nuts were eaten without any further cooking or preparation

Medicinal Uses

The seeds, when mashed, were used by the Costanoan and Kawaiisu groups as a salve or suppository treatment for piles (hemorrhoids).

An infusion of the bark was used to treat toothaches by the Costanoan. Maidu, Pomo, Yuki, and Mendocino Indians treated toothaches and loose teeth by placing a piece of bark directly in the mouth without first infusing it.

Bark was taken from around the base of a California buckeye and used to make a poultice for snake bites by the Pomo. Similarly, the Wintun used smashed buckeye fruits as a general poultice for wounds.

Mendocino Indians fed the nuts to horses as a treatment for bot worms. The nuts were also known to induce abortions in pregnant cattle if eaten in sufficient quantity.

Other Uses

Fish Poison

  •  Buckeye nuts were used to make fish poison. This was done by crushing the raw nuts, often using one’s feet, and then putting the mashed product into ponds or small streams. The smashed, raw nuts have a stupefying effect on fish, which then float to the surface, to be easily collected by hand or net. Rinsing the fish afterwards removes the poison, rendering the fish edible. This method was used by the Ohlone, Pomo, Mono, Maidu, Costanoan, Esselen, and other groups.
  • The leaves, particularly the tender young ones, were used to make fish poison by the Concow, Monache, and Yuki groups.


  • Bows made of California buckeye were used by the Gabrielino, Miwok, Pomo, and Wappo.
    • The Gabrielino used their bows for hunting small game animals.
    • The Wappo considered California Buckeye to be the second-best material from which to make bows; manzanita (Arctostaphylos) was considered the best bow material.
  • Maidu made arrows from the straight, young shoots.


  • Narrow drills for hollowing out arrow mainshafts were made and used by the Yokuts.
  • The young shoots (age 1-3 years) of California Buckeye were used as fire drills by the Miwok, Maidu, Pomo, Sinkyone, Wappo, Wintun, and Yana.
    • The Wintun used buckeye drills together with hearths made of juniper (Juniperus) wood.

Firewood and Hearths

  • Mature buckeye stems were used as firewood by the Miwok.
  • Hearths were made from mature buckeye stems by the Maidu.
    • Buckeye hearths used as part of a fire drilling set were utilized by the Miwok, Pomo, Yana, and Yuki.
  • Old, rotten wood, once dry, was used as tinder by the southern and central Miwok.


Charcoal made from buckeye wood was mixed with water to make black paint by the Pomo. It is also thought to have been used as a dye in Pomo basketry.


  • The long, straight, young shoots were used as a basketry material by the Maidu.


‘Aesculus’ was used by Carl Linnaeus, and is derived from the old Roman name for the durmast oak (Quercus petraea), an unrelated species.

‘Californica’ simply means ‘from California, USA’.


The following are names used for A. californica by various Native American groups:

  • Cahto/Kato: laci, laashii’, lashee’
  • Kawaiisu (Tehachapi): paɁasvƗ
  • Maidu: poló
  • Miwok (coast): ah’ te
  • Miwok (central sierra): siwu, siwü
  • Miwok (plains): ʔu·nu-
  • Nisenan: polo
  • Nomlaki: pasa, fär’sökt, bok; khlup (meaning “sacred broth porridge of roasted buckeyes boiled in sand pools with hot stones”)
  • Pomo: dē sä’  kä lā’
  • Pomo (northern, southwestern): bace
  • Pomo (southwestern): bash’e (tree), unu (nuts)
  • Pomo (central, southern): baca’
  • Pomo (southern): be’ce, bahša (pronounced sort of like ‘bah-sha’).
  • Wappo: sumoto
  • Wintu: yonot
  • Yana: pa’s I (used specifically in reference to the nuts)
  • Yokia: bä shā’
  • Yuki: simpt’ol, simpt’ ōl, simpti ol, si’ mt


Cambridge University Botanic Garden Website:

National Council for the Conservation of Plants and Gardens (NCCPG):

General Information (Books):

  • Moerman, D. (2009). Native American Medicinal Plants. 1st ed. Portland, OR: Timber Press. (Page 50). ISBN 9780881929874
  • Moerman, D. (2010). Native American Food Plants. 1st ed. Portland, OR: Timber Press. (Page 33-34). ISBN 9781604691894
  • Welch, J. (2013). Sprouting Valley: Historical Ethnobotany of the Northern Pomo from Potter Valley, California. 1st ed. Denton, TX: Society of Ethnobiology. (Page 51-52). ISBN 9780988733022
  • Mead, G. (2014). The Ethnobotany of the California Indians. 2nd ed. La Grande, OR: E-Cat Worlds Press. (Page 23-26). ISBN 9780989092791
  • Timbrook, J. (2007). Chumash Ethnobotany. 1st ed. Santa Barbara, Calif: Santa Barbara Museum of Natural History. (Page 25, 153). ISBN 9781597140485
  • Govan, G., Govan, L., and Oswalt, E. (2008). California Natives: Plants & People A Self-Guided Tour. Berkeley, CA: University of California Botanical Garden. (Page 24).
  • Baldwin, G., Goldman, D., Keil, D., Patterson, R., Rosatti T., and Wilken, D. (2012). The Jepson Manual of Vascular Plants of California. Berkeley, CA: University of California Press. (Page 1231). ISBN 9780520253124
  • Balls, E. (1972). Early Uses of California Plants. 1st ed, 4th printing. Berkeley, CA: University of California Press. (Page 14).
  • Smith, K. (2014). Enough for All: Foods of My Dry Creek Pomo and Bodega Miwuk People. 1st ed. Berkeley, CA: Heyday. (Page 118). ISBN 9781597142427
  • Brockman, F., illustrations by Merriless, R. (1968). Trees of North America. 1st ed. New York, NY: Golden Press. (Page 220).
  • Howell, T. (1985). Marin Flora. 2nd ed. Berkeley, CA: University of California Press. (Page 188). ISBN 0520056213
  • Anderson, K. (2006). Tending the Wild. 1st ed. Berkeley, CA: University of California Press. (Page 137, 220). ISBN 9780520248519
  • Mabberley, D. (2009). Mabberley’s Plant-Book. 3rd ed. Cambridge, UK: Cambridge University Press. (Page 17). ISBN 9780521820714

General Information (Web References):


  • Rose, W. (2002). Itch Like Crazy. 1st ed. Tucson, AZ: The University of Arizona Press. (Page 85). ISBN 0816521778


  • Gledhill, D. (2008). The Names of Plants. 4th ed. Cambridge University Press. (Page 38, 84). ISBN 9780521685535



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