California buckeye Aesculus californica
California buckeye (Aesculus californica) is a deciduous perennial tree in the Sapindaceae family, native to Foothills and canyons of California. It grows 4–10 m (13–33 ft) tall and 5–10 m (16–33 ft) wide, wants full sun and low water, and is hardy to about -12 °C (10 °F). Space plants about 6 m (20 ft) apart.
Plan California buckeye in your garden →
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California buckeye at a glance
| Type | Perennial tree, deciduous |
|---|---|
| Family | Sapindaceae |
| Mature height | 4–10 m (13–33 ft) |
| Mature spread | 5–10 m (16–33 ft) |
| Spacing | 6 m (20 ft) centre to centre |
| Sun | Full sun, at least 6 h of direct sun a day |
| Water | Low; drought tolerance high, waterlogging tolerance none |
| Soil pH | 6–8 |
| Cold hardiness | About -12 °C (10 °F) once established (roughly USDA zone 8) |
| Heat stress | Likely above about 42 °C (108 °F) |
| Flowering | from about May for 4–6 weeks (northern hemisphere; later in cold climates, earlier in warm ones) |
| Wind tolerance | Moderate |
| Pollinator value | High |
| Edible | Not grown as food |
| Native to | Foothills and canyons of California |
| Common in gardens of | 🇺🇸 United States, 🇬🇧 United Kingdom |
Is California buckeye toxic?
- People: severely toxic
- Cats: moderately toxic
- Dogs: moderately toxic
- Parts: seeds, leaves, flowers (nectar)
The big seeds contain aesculin and other poisons; Native peoples leached them for many days before eating them. The nectar is toxic to honeybees (but not to native bees).
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with California buckeye
No well-documented helpful pairing. Group it with plants that like full sun and low water.
Questions about California buckeye
- How far apart should I plant California buckeye?
- About 6 m (20 ft) apart, centre to centre. A mature plant spreads 5–10 m (16–33 ft).
- Does California buckeye need full sun?
- Full sun: at least 6 hours of direct sun a day.
- How much water does California buckeye need?
- Low water. Drought tolerance is high and waterlogging tolerance none.
- How cold-hardy is California buckeye?
- It tolerates about -12 °C (10 °F) once established, roughly USDA zone 8.
- When does California buckeye flower?
- From about May for 4–6 weeks (northern hemisphere; later in cold climates, earlier in warm ones).
- Is California buckeye poisonous to cats and dogs?
- For cats it is moderately toxic; for dogs moderately toxic; for people severely toxic. The big seeds contain aesculin and other poisons; Native peoples leached them for many days before eating them. The nectar is toxic to honeybees (but not to native bees).
- What grows well with California buckeye?
- There is no well-documented companion pairing for California buckeye. Group it with plants that like the same sun (full sun) and water (low).
Sources and evidence
Evidence grade A (A: strong evidence).
- Plants of the World Online (taxonomy, native range), Royal Botanic Gardens, Kew
- Calscape: California native plants, California Native Plant Society
- Calflora: information on California plants, Calflora (non-profit database), Berkeley, California
Notes and assumptions
- A California native of the chaparral and foothills: it grows through the mild, wet winter and rests in the dry summer, when it should be left unwatered once established.
- A broad, low tree with candles of fragrant creamy flowers in late spring, then drops its leaves in midsummer drought, leaving silver branches hung with large pear-shaped pods; the earliest tree to leaf out each winter.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
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