How To Grow And Care For Bottlebrush Buckeye

Native to the southeast but adapted to a much larger area, bottlebrush buckeye (Aesculus parviflora) gets its name from showy, summer white blooms that resemble bottlebrushes and its dark, shiny, inedible seeds that remind you of chestnuts or buckeyes. In the wild, you usually find it growing in the shady forest understory—the shrub slowly suckers, but not aggressively, forming colonies up to 12 feet tall.

Twelve-inch bloom spikes stand atop the foliage in June and July. A big bottlebrush buckeye can be quite the sight. But the show doesn't end in summer. In fall, large, palmate leaves of five to seven leaflets change from deep green to glorious bright yellow. While beautiful, this plant is toxic to animals and people.

Plant Attributes

Bottlebrush Buckeye Care

People often expect the prettiest plants to be a pain to grow, but that certainly isn't the case here. Bottlebrush buckeye needs moist, well-drained soil, partial to full shade, and pests rarely impact it. It thrives in USDA Zones 5 to 9. Keep the soil consistently moist while growing and use organic fertilizer to maintain the soil's pH monthly from spring to fall for young plants.

Light

Bottlebrush buckeye grows well in partial shade. Plants growing in sunlight are usually less susceptible to disease, but too much sun exposure can burn plants, especially young plants.

Soil

The best soil for bottlebrush buckeye is rich in nutrients, well-draining, and ranges from slightly acidic to slightly alkaline. Bottlebrush buckeye has an extensive root system, so ensure a deep planting location for the plant to expand.

Water

Keep bottlebrush buckeye consistently moist when establishing its roots and throughout its growing season. Stop watering in the winter to help prepare the roots for dormancy. After young plants develop, the bottlebrush buckeye is relatively drought-tolerant but cannot sustain harsh summer heats without extra irrigation.

Temperature and Humidity

Bottlebrush buckeye prefers moderate temperatures and a moist growing environment—keep temperatures between 50°F to 80°F.

Fertilizer

Before planting, add organic fertilizer to the soil to create a nutrient-rich ground. Continue adding a monthly fertilizer to help young plants mature from spring to fall. Start with a 20-20-20 fertilizer and switch to a 10-30-20 to prepare the plant for colder temperatures. Mature plants do not need as much fertilization, typically two or three times a year.

Types of Bottlebrush Buckeye

There are several bottlebrush shrub and tree varieties. Here are some types to know:

• 'White bottlebrush' (Callistemon salignus): This variety requires little pruning and grows up to 25 feet tall and 15 feet wide. This plant is also known as the willow bottlebrush.
• 'Crimson bottlebrush' (Callistemon citrinus): Also known as the lemon bottlebrush or common red bottlebrush, this plant is deer-resistant and drought-resistant.
• 'Prickly bottlebrush' (Callistemon brachyandrus): This plant variety has red, spiky flowers and thrives in warm, dry climates. 

Pruning

It is unnecessary to prune bottlebrush buckeye, but the best time is between late winter and early spring, as you are less likely to damage the plant. Light pruning in the fall can help remove diseased, damaged, or overgrown branches. Prune to enhance the health or size of the plant and promote its growth. Remove unnecessary branches to help promote better air circulation. Deadheading spent blooms can also help provide better air circulation while exposing the inner branches to the sunlight.

Propagating Bottlebrush Buckeye

Because it suckers, it's an easy shrub to propagate by division in fall or winter. Here is how to propagate bottlebrush buckeye using suckers:

1. Carefully dig around the sucker's root and loosen the soil—be careful not to disturb the parent plant's roots. 
2. Cut the sucker using sterile gardening shears from a healthy plant where it connects to the main branch. 
3. Return the parent plant without disturbing its roots and gently pack the surrounding soil. 
4. Using a sharp knife, trim the base of the sucker where it meets the main root. 
5. Remove the bottom half of the leaves or leafy shoots. 
6. Plant the sucker into moist, well-draining soil rich with organic matter such as compost or manure. 
7. Water deeply and use fertilizer if preferred during the time of planting. 

How to Grow Bottlebrush Buckeye From Seed

It's easy to start from seed, but there's a trick. You must harvest the seeds as soon as the seed husks open and drop to the ground—don't wait until they dry out. Here's how to grow bottlebrush buckeye from seed:

1. Harvest the seeds from an existing plant or purchase them from a garden center. Place the seeds in a brown paper bag and leave them in a warm, dry location for a few days. 
2. Use a seed-starting tray to sow the seeds directly into moist, fertile soil or potting mix. Use your hands to loosen the soil and make holes a few inches deep. 
3. Lightly cover the seeds with soil and water deeply after planting. 
4. Cover the seed-starting tray with plastic wrap or a bag to increase the humidity and promote growth. 
5. Within two weeks, new growth will emerge. Continue growing seeds in full sun—at least six hours daily. 
6. Continue watering and add plenty of drainage soils until the plants are ready to move outdoors. 

Overwintering

Prepare for winter by decreasing the frequency of watering to prepare for dormancy. Bottlebrush buckeyes need cold exposure in the winter to produce a healthy spring plant. Remove fallen leaves or branches around the plant to prevent pest infestations and diseases from establishing.

Common Pests & Plant Diseases

Pests such as Japanese beetles can become a problem for these plants by feeding on the leaves and stripping the branches bear. Keep plants weed-free to avoid beetle infestations, and hand-pick remaining pests if the problem persists.

While relatively disease-resistant, bottlebrush buckeye is susceptible to canker, leaf spot, anthracnose, rust, and powdery mildew. Maintain plenty of sun exposure and well-draining soil to prevent these diseases from developing. 

Common Problems With Bottlebrush Buckeye

Bottlebrush buckeye is an easy-to-grow plant, but some issues may present themselves from improper care. Here's what you should know:

Leaves Turning Yellow

The most common issue for yellowing leaves is nutrient deficiency. Yellowing leaves may begin at the plant's base or top. Provide plants with a monthly fertilizer to maintain soil quality. Additionally, using a water-soluble fertilizer will help keep nutrient levels steady in young plants as they need consistent watering. Some diseases can also cause yellowing leaves, such as root rot fungus, which causes the plant to die back if not removed.

Flower Wilting

Depending on the plant's growing season, wilting flowers may be routine or caused by an unexpected environmental change. Deadheading can keep the plant healthy until the following season showing if flowers are spent and wilting after blooming. An unexpected drop in flowers can result from insufficient water, nutrient deficiencies, or water-logged roots. When watering the plant, water at the base and avoid wet leaves, as this increases the chance of a bacteria or fungus from developing. Dispose of damaged or diseased branches away from healthy plants.