California buckeye

Sun

Full sun to light partial shade; flowering and branching are best in sun.

Water

Low once established in a suitable climate. Water young trees deeply during dry spells; established trees usually need little summer irrigation.

Soil

Well-drained soil, including clay, loam or stony ground; tolerates relatively poor soil but not prolonged waterlogging.

Height

15-40 ft (4.6-12.2 m)

Spread

20-40 ft (6.1-12.2 m)

Flowers

Late spring to early summer; upright spikes of fragrant white to pale pink flowers.

Foliage

Large, palmately compound leaves, usually with five to seven toothed leaflets. Leaves emerge early and may yellow and drop in midsummer in hot, dry conditions.

Growth

Slow to moderate

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Heat tolerant
• Low allergen
• Fragrant

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   7 ft (2 m)

2. After 1 year

   7 ft (2.2 m)

3. After 2 years

   8 ft (2.5 m)

4. After 3 years

   9 ft (2.7 m)

5. After 5 years

   11 ft (3.2 m)

About 26 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Toxic

Native to

the US

Growth rate

Slow

• Plant during the cool, wetter season, allowing room for a broad crown and low branches.
• Water deeply through dry spells during the first two or three growing seasons, letting the soil begin to dry between waterings.
• Once established, avoid frequent lawn-style irrigation, particularly around the trunk.
• Spread 2-3 in (5-8 cm) of organic mulch over the root zone, keeping it clear of the trunk.
• Do not routinely fertilise; feed only if a soil test identifies a deficiency.
• Collect fallen seeds where children, pets or grazing animals could reach them.

Pruning. Prune lightly in late winter before growth starts, removing dead, damaged or crossing branches. Establish the main framework while young, and avoid topping or repeatedly cutting back mature limbs.

Autumn

Collect fallen seeds from paths and areas used by children or animals; sow fresh seed promptly if propagating.

Late autumn

Plant when the soil is moist and workable, provided it is not waterlogged or frozen.

Late winter

Remove damaged or crossing branches before the early leaf growth begins.

Spring

Refresh mulch and check that it is not touching the trunk.

Late spring

Check soil moisture around recently planted trees as rainfall decreases.

Summer

Water young trees deeply during drought; accept summer leaf drop on established trees rather than trying to reverse it with frequent watering.

• Use as a specimen in a spacious dry garden, where its broad crown and pale bark can be seen clearly.
• Combine with drought-tolerant California native shrubs and bunchgrasses that share its low summer water needs.
• Place on a well-drained slope for a natural, open-woodland effect.
• Set against dark evergreen planting to highlight its bare branching structure after leaf fall.

Garden styles it suits: California native, Mediterranean, Desert / xeriscape, Woodland, Low-maintenance and Winter interest.

Plant it with: Toyon, Manzanita, California lilac, Deer grass, Purple needle grass and California fuchsia.

Wildlife: Flowers attract native bees and other insects. Nectar and pollen can poison honeybees, particularly where alternative forage is scarce, so this is not a suitable tree to plant specifically for honeybee forage.

• Early summer leaf yellowing and drop: usually normal drought dormancy, not a disease; check establishment and soil moisture before adding water.
• Root and crown rot in wet soil: improve drainage, keep mulch away from the trunk and stop frequent summer irrigation.
• Powdery mildew or leaf blotches: allow good air circulation and clear fallen affected leaves; established trees rarely need treatment for minor damage.

Toxic to people, dogs, cats and horses if eaten. All parts should be treated as poisonous, especially the seeds and young growth; ingestion can cause vomiting, diarrhoea, weakness and serious neurological signs. Seek urgent medical or veterinary advice after suspected ingestion.

• Horse chestnut (Aesculus hippocastanum)

  Usually a much larger tree, with larger leaves and prickly green fruit husks; California buckeye has smooth, pear-shaped husks and often becomes bare during summer drought.

• Ohio buckeye (Aesculus glabra)

  Has yellow-green flowers and usually prickly or warty fruit husks, rather than California buckeye's white to pale pink flowers and smooth husks.

• Sweet chestnut (Castanea sativa)

  Has simple, long, sharply toothed leaves and nuts enclosed in densely spiny burrs; California buckeye has hand-shaped compound leaves and poisonous seeds in smooth husks.

The species name californica refers to California, while buckeye describes the brown seed with its pale scar, resembling a deer's eye.

Propagation. Grow from fresh, mature seeds collected after the husks split in autumn. Do not let seeds dry out; sow promptly in deep pots protected from rodents, and plant out while young because the developing roots dislike disturbance.

Accepted botanical name

Aesculus californica

In the US and Canada

Native in the lower 48 states.

Native range

California and Oregon.

Measured

Soil pH 5.5 to 7.5. Average height 914 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.