California Buckeye (Aesculus californica)

Buckeye, California Buckeye

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Planting California buckeye trees is a great way to add shade and visual interest to the home landscape. Growing California buckeyes is not only easy but also provides habitat for native wildlife and pollinators. With knowledge of a few California buckeye facts, homeowners will be able to make a more informed decision regarding whether or not this tree is a good choice for their yard.

I. Appearance and Characteristics 

Aesculus californica, commonly known as the California buckeye or California horse-chestnut, is a species of buckeye native to California and southwestern Oregon.

Aesculus californica is a large deciduous shrub or small tree, up to 4–12 m (13–39 ft) tall, with gray bark often coated with lichens and mosses. It typically is multi-trunked, with a crown as broad as it is high. Trees are long lived, with an estimated lifespan between 250–280 (300 maximum) years. The leaves are dark green, palmately compound with five (rarely seven) leaflets. Each leaflet is 6–17 cm (2.4–6.7 in) long, with a finely toothed margin and (particularly in spring) downy surfaces. The leaves are tender and prone to damage from both spring freezing or snow and summer heat and desiccation.

The flowers are sweet-scented, white to pale pink, borne on erect panicles 15–20 cm (6–8 in) long and 5–8 cm (2–3 in) broad. The fruit is a fig-shaped capsule 5–8 cm (2–3 in) long, containing a large, round, orange-brown seed, measuring 2–7 cm (0.8–2.8 in). The seeds are poisonous and are the largest known of any temperate (non-tropical) plant species.

A. californica has adapted to its native Mediterranean climate by growing during the wet late winter and spring months and entering dormancy in the dry summer months, though those growing in coastal regions tend to hold on to their leaves until mid-autumn.

It is found growing in a wide range of conditions from crowded, moist, semi-shaded canyon bottoms to dry south-facing slopes and hilltops. In the coastal ranges north of Big Sur it is found growing alone on slopes, or intermingled with valley oak (Quercus lobata), Oregon oak (Q. garryana), coast live oak (Q. agrifolia) and California bay laurel (Umbellularia californica). In the foothills of the Sierra Nevada, A. californica can be found standing alone in grassland at the lowest elevations, intermingled in blue oak woodlands at intermediate elevations, and in mixed evergreen forests of black oak (Q. kelloggii), gray pine (Pinus sabiniana), ponderosa pine (P. ponderosa) and interior live oak (Q. wislizeni) as it nears the limit of its range.

California Buckeye (Aesculus californica)

II. How to Grow and Care

Sunlight

California buckeye requires sunlight to grow. It can grow in partial shade to full sun. A position facing the sun is the most preferred, especially in the seedling stage, when sufficient sunlight is essential. In the shade, these plants are usually thin and prone to disease.

In hot summers, be wary of direct sunlight burning the plants. To avoid sunburn, put up shade nets for young trees. Large trees can be protected by painting their trunks white in late fall or early summer, or by covering the base of the trunk with organic mulch.

Watering

After transplanting a california buckeye tree, the soil needs to be kept moist to encourage rooting. During the growing period, irrigate according to the weather conditions. If there is little rain, dry weather, and strong transpiration in early spring, give more water; if it is during the rainy season, stop irrigation. Add water during early flowering, late flowering, and fruiting periods. At the beginning of winter, water once and then stop. This promotes stronger trunks.

Generally, mature california buckeye trees do not require watering, but if there is a prolonged drought, add more water as needed. If the leaf edges appear scorched, water and spray the plant more frequently.

Soil

California buckeye roots are deep and extensive, so its planting location requires a deep soil layer. It grows well in fertile, well-drained, slightly acidic to neutral (pH 5.5-7) sandy soil. Although it can also grow in light saline soil, its growth won’t be as good.

Fertilizing

Before transplanting, apply a well-rotted organic fertilizer to the soil pit and mix it well with the soil to provide nutrition for the young tree’s growth. For the rapid growth of young plants, fertilize once a month from spring to fall. From spring to summer, use a fertilizer that contains roughly equal proportions of the three main elements (N:P:K=20:20:20); in fall, you can switch to a high phosphorus-potassium fertilizer (N:P:K=9:45:15 or N:P:K = 10:30:20). This improves the cold and stress resistance of the tree. A well-rotted organic fertilizer can be applied once in late fall to provide nutrients for the second year of growth.

For mature trees, fertilization is determined by the growth of the plants. Generally, you can fertilize 2-3 times a year. If the soil is fertile, no fertilization may be needed. To fertilize, dig a 30 to 40 cm-deep circular trench at the edge of the vertical projection of the canopy. Sprinkle fertilizer into it and mix it slightly when backfilling the soil. Use radial trenches to fertilize big trees older than five years. Dig a few 15 to 40 cm-deep trenches from the edge of the tree trunk to the periphery, and, again, sprinkle fertilizer into the trench and mix it slightly with the backfill soil.

Planting Instructions

It’s best to transplant one-year-old seedlings in spring. When transplanting, dig deep pits and apply base fertilizer. Since california buckeye has a taproot system and there are few fibrous roots, root balls must be transplanted whole to minimize root damage. If subsequent transplanting is planned, maintain a distance of about 1.5 m between small trees; if the position is fixed and the trees won’t be moved, maintain a distance of at least 4 m. Keep the soil moist after planting small trees to prevent the buds from drying up.

If you buy a large sapling that has been growing for several years, prune some branches before transplanting to reduce water evaporation and keep the sapling hydrated. You can prune overgrown, diseased, or damaged branches to about one-third of the original branches of the canopy.

In addition, remove some of the leaves to reduce water evaporation. Large saplings need to be transplanted with soil. The size of the root ball is generally 7-10 times the diameter of the seedling at breast height. Dig a pit 50 to 60 cm deep, and keep trees at least 4 m apart. After planting, compact and water the soil thoroughly.

Pruning

Usually California buckeye trees do not need pruning, because its natural crown is round and it is better to keep the original crown shape. Light pruning can be carried out after the fall of leaves: over-long branches can be shortened, over-dense branches can be thinned, and diseased or dry branches can be completely removed. This avoids the consumption of excess nutrients, allows more light to reach the plant’s interior, is conducive to its healthy growth, promotes the air circulation inside the plant, and effectively reduces disease.

Transplanting

Transplanting the california buckeye thrives in early spring (referred here as S3) to late spring (termed S4), harnessing the season’s optimal growth conditions. Encouragingly chose a sun-dappled spot, offering morning sun and afternoon shade. Remember to maintain enough spacing between plants to ensure proper air circulation.

III. Uses and Benefits 

Native American tribes, including the Pomo, Yokuts, and Luiseño, used the poisonous nuts and seeds to stupefy schools of fish in small streams to make them easier to catch. The bark, leaves, and fruits contain the neurotoxic glycoside aesculin, which causes hemolysis of red blood cells. Buckeye also makes a good fireboard for a bow drill or hand drill.

Native groups occasionally used the plant as a food supply; after boiling and leaching the toxin out of the seeds or nut meats for several days, they could be ground into a flour or meal similar to that made from acorns. The nectar and pollen of the flowers is toxic to honeybees, so the trees should not be planted near apiaries. When the shoots are small and leaves are new, they are lower in toxins and are grazed by livestock and wildlife. The flowers are a rich nectar source for many species of butterflies, and squirrels and chipmunks consume the seeds. Hydroquinone and epicatechin have been isolated from the seeds and have been shown to have allelopathic properties by inhibiting plant growth.

It is used as an ornamental plant for its striking leaf buds, lime green foliage, fragrant white flowers, red-brown foliage in mid to late summer, and architectural silver branches through fall. The tree also acts as a soil binder, which prevents erosion in hilly regions.

California Buckeye (Aesculus californica) Details

Common name

Buckeye, California Buckeye

Botanical name

Aesculus californica

Family

Sapindaceae

Species

californica

Origin

California

Life cycle

Plant type

Hardiness zone

,

Sunlight

Drainage

Growth rate

Harvest time

Flowering period

Height

15 ft. – 30 ft.

Width

15 ft. – 30 ft.

Flower color

Leaf color

Fruit color

,

Flower benefit

Garden style

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