If you see a brown-leaved or bare tree in striking contrast to its green leafy neighbors in Midpen preserves this summer, it’s likely an endemic California buckeye (Aesculus californica), sometimes called a horse chestnut. From late summer through February, these slow-growing, drought-adapted hardwoods drop their leaves and go dormant. You’ll see their bare branches hung like ornaments with pear-shaped fruits containing large, glossy brown seeds that will eventually drop to the ground.
Local Native Americans incorporated the seeds into their diet by leaching out their poison with boiling water. They also used the poison to stun fish. When winter rains return, buckeyes leaf out again in pale green, and eventually bloom with large candelabra-like spires of fragrant white flowers.