Jepson (2012) (APG System)

Order

Sapindales

Family

Sapindaceae

Jepson (1993) (Cronquist System)

Order

Sapindales

Family

Hippocastinaceae

Plant Relationships

California Species:

Aesculus californica

(California buckeye)

Other Species:

Aesculus glabra
Aesculus hippocastinum

(Ohio buckeye)
(Horse chestnut) (europe)

Description

Growth Forms:

Aesculus californica is a tree.

Branching:

Opposite branching

Leaves:

Aesculus is palmately compound. This species has the unusual habit of avoiding the summer drought by losing its leaves during the summer. The leaves emerge in the winter around early March and fall off sometime in July or August.

Flowers:

Aesculus flowers are showy, in panicles or racemes.

Fruit:

Buckeye seeds are large and heavy, between 1 and 2 inches across. The seeds ripen in October or November.

Growing Conditions

Natural Range and Habitat:

People consider buckeye a riparian plant, and that is where they are typically used in restoration projects, but most buckeyes are found at the edges of open woodlands in the full sun, often on north or east facing slopes. These particular locations have a good moisture supply.
If buckeye is found in a riparian zone, it is in a sunny, exposed area where there are few other trees to compete with. This could be a high spot, slope or area with poor soil that does not support other trees.
Buckeyes are often found within north and east facing grasslands or at the edges of grasslands.
A notable outlier location is the Vasco Caves in eastern Contra Costa County between Brentwood and Tracy. This is a hot, exposed location, where no other trees grow. The buckeyes are evidently benefitting from the moisture captured in the rock formation. They lose their leaves in the early summer, so avoid the problem of the extremely dry, hot summer.

Sun and Exposure:

Buckeyes require full sun to grow. Branches that become shaded usually die back.

Soil and Moisture:

Buckeyes grow in sites with an easily accessible water supply, but they don't grow in wet soils. They seem to prefer well drained locations within riparian zones or on hillsides with a adequate subsurface moisture.

Horticulture and Restoration

Horticultural Comments:

This is an attractive, medium to small tree that makes a great addition to the landscape. The flower clusters are attractive, and last for many weeks.

Wildlife Habitat:

The flowers and seed of buckeye produce toxic compounds to deter wildlife. The flowers produce pollen which is safe to native pollinators, but toxic to european honeybees. The seeds and large and look like chestnuts, but are left behind by squirrels and deer. They remain on the ground to germinate or to decompose in place.

Restoration Projects:

Buckeye is most often used in riparian projects. It does poorly where the soil is waterlogged for long periods of time, but grows well where the soil is drained.
Consider using buckeye on north facing hillsides in the region just above the riparian zone.