Answering the Seasonal Question, "Is That Tree DEAD?"
During the summer months, Nature Center visitors often ask whether the large tree out front has died. The California Buckeye (Aesculus californica) is a native, widely distributed California tree known for its broad, multi-branched form. In early summer, its leaves begin turning orange-brown and remain attached until fall, when hanging fruits containing buckeye seeds enclosed in greenish husks become more visible. Rather than dying, the tree has adapted to California’s hot, dry summers by entering a dormant state until cooler temperatures and seasonal rains return.
The tree’s name comes from its seed. Once the husk falls away, the smooth brown seed is revealed, marked with a pale “eye” that resembles the large brown eye of a deer—or buck—giving rise to the name “buckeye.”
After falling to the ground, the seed waits for rainfall before sending out roots into the softened soil. Soon after, new leaves begin to sprout. Mature buckeye trees are among the first to leaf out in January or February following winter rains.
As the canopy fills with green leaves, long, candle-like flower clusters emerge, releasing a sweet fragrance that attracts butterflies and moths. These pollinators help continue the cycle as the fertilized flowers develop into husk-covered buckeyes.
For Indigenous peoples of California, including the Plains Miwok and Valley Yokuts of this region, buckeyes were an important resource. Crushed seeds were traditionally used in streams to temporarily stun fish. Although the seeds are toxic and not generally edible, they could be processed extensively to remove tannins and toxins during times when acorns were scarce. Buckeye wood was also used for making bows and arrows.
The seeds remain toxic to most animals, yet California Ground Squirrels—also known as Beechey Ground Squirrels (Otospermophilus beecheyi)—are often seen eating them. While the flowers are toxic to non-native honeybees, native bees, butterflies and several moth species feed on the nectar and assist in pollinating the small blossoms.
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