California buckeye - Aesculus californica

In brief

Aesculus californica, Sapindaceae.

- Deciduous tree or large shrub, to 12 m
- Endemic to California
- Flowers May and June
- Fruit a large capsule holding one glossy seed

Where it grows

Foothill woodland and canyon bottoms through the Coast Ranges and the Sierra Nevada foothills, usually near water. Here it grows down by Buckeye Falls, which carry its name.

When it blooms

May and June, in erect white panicles held above the leaves like candles.

Seed and fruit

A pear-shaped capsule that splits to a single large glossy brown seed. The seed is toxic raw, and leaching it with water is how it became a food in California long before there was an orchard on this hill.

Here

Photographed in flower by the creek on June 8, 2021, and holding brown leaves on August 30, 2026.

It is the first tree here to come into leaf and the first to shut down. Brown leaves at the end of August are not a tree dying: it spends the dry end of the year with no leaves at all instead of spending water on them.

Worth knowing where there are hives. The nectar and pollen are toxic to honey bees, which are not from here and did not grow up with it. The native bees work it without harm.

Brown in August

The fruit is already on the tree while the leaves around it are going brown. This is drought avoidance, not fall, and it happens two months before the black oak turns.

Green buckeye fruit hanging among leaves that have gone brown

Green fruit and brown leaves on the same branch, August 30, 2026.

A split buckeye capsule holding one glossy brown seed, on a bare branch

November 14, 2022.

One seed to a capsule

By November the tree is bare and the capsule has opened. What is inside is a single seed, glossy and brown and about the size of a chestnut, which is what the other name is about.

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