Japanese Maple Care Tips

Types of Japanese Maple:

Bloodgood: 15-20’ x 14-30’
Emperor I: 15' x 15'

Fireglow: 20' x 15'
Red Sentinel: 10-15’ x 6-8’

Sango Kaku: 20-25' x 10-15’

Japanese maples thrive in a balance of light and shade, which enhances their vibrant leaf colors and prevents sunburn. While they can tolerate full sun in mild climates, hotter regions require more shade and consistent watering to avoid leaf scorch. Protect them from strong winds and plant in well-drained soil. Avoid summer planting due to their sensitivity to heat; early spring or fall is ideal, depending on your climate. Japanese maples thrive in moderately to slightly acidic soil with a pH between 5.5 and 6.5.

When planting keep your soil type in mind if your soil needs to be amended do so. Do not cover the bud onion. When planting make sure the root ball is above level ground by 2 inches to prevent root rot or fungus.

Fertilizing:

Apply a balanced fertilizer formulated for acid-loving plants in early spring before new growth appears. Avoid over-fertilizer & follow fertilizer instruction.

Pruning:

Prune Japanese maple is in late winter when the tree is dormant. For fine pruning for aesthetic purposes, wait until late spring after the leaves have emerged. When pruning, focus on removing dead or damaged branches, particularly from the tree’s interior, as well as any branches that cross or rub against each other. This promotes better air circulation & allows more light to reach the canopy. Make clean cuts back to lateral branches or buds for optimal results, and avoid drastic reshaping, which can create noticeable gaps in the tree. With Japanese maples, less is more. Take your time, remove only the dead branches, and let the tree maintain its natural beauty.

Sprayer Use:

• A pump-up sprayer is recommended.
• Avoid leaving chemicals in the sprayer after use.

Seasonal Adjustments:

• Reduce spraying during hot summer months following chemical instructions.

Watering Systems:

• Avoid overhead watering to minimize fungal leaf issues.
• Use drip irrigation as the best method for watering.

Brown & Curling in leaves

• Underwatering: Japanese maples need moist, well-drained soil. In hot weather, lack of water can cause leaves to dry out, brown, and curl.

• Overwatering: Too much water can suffocate roots, leading to wilting and browning despite wet soil.

• Excessive Sun: Some varieties tolerate full sun, but others need afternoon shade. Intense summer sun can scorch leaves, causing browning and curling.

• Pests/Diseases: Insects or fungal issues, though less common, can also harm leaves, leading to similar symptoms.

If your Japanese maple’s leaves develop crispy edges by fall due to a tough summer or occasional missed watering, there’s no need to worry. As long as the leaves were healthy for most of the year, the tree will shed them naturally and rejuvenate with fresh growth in the spring.

Powdery Mildew

Powdery mildew spreads through the air and doesn’t require water to infect plants. It overwinters in soil debris and thrives in mild temperatures with high nighttime humidity. Infection typically occurs from mid-summer to fall, often causing early leaf drop in severe cases. Though mostly aesthetic, this disease is rarely fatal to plants.

Identify: Powdery mildew appears as white, dusty growth on leaf surfaces, with black fruiting bodies on the undersides of infected leaves.

Treatment: Powdery mildew can infect plants even in dry conditions, but good aircirculation helps prevent it. Prune overlapping, dead, or damaged branches, andspace Japanese maples 6–20 feet apart based on their mature size. Remove fallen leaves from infected trees to stop the pathogen from overwintering. Foryoung or stressed trees, consider using a registered fungicide as directed.

Root Rot

Root rot thrives in wet conditions from poor drainage, flooding, or over watering. Early symptoms mimic nutrient deficiencies or watering problems, including slow growth and yellowing or blackening leaves. Progressing to branch & root dieback, eventually killing the tree. Root rot pathogens can persist in soil & plant debris for extended periods.

Identify: Root rot is identified by decaying tissue at the soil line and roots, with the vascular cambium turning brown and mushy instead of green when bark near the lower trunk is peeled back.

Treatment: Preventing root rot is key. Avoid planting Japanese maples in areas with poor drainage, and amend heavy clay soils with organic matter. Water only when the soil is dry, and keep mulch away from the trunk. Remove and destroy infected plants. Fungicides can help prevent root rot but are not curative.

Verticillium Wilt

Verticillium Wilt remains dormant in the soil and enters through wounds in the roots or tree buttress, affecting the current year’s growth. It blocks water- conducting vessels, restricting water flow to the branches and leaves. The tree responds by further blocking these vessels with gums, worsening the restriction. While large trees may survive for years with mild symptoms, infected trees often die within 2 to 3 years.

Identify: Heavy seed production, smaller-than-normal leaves, & browning leaf margins. Often, only one side of the tree wilts. The wood under the bark of wilting branches shows discoloration: green-black in maples, brown in elms, & brown to black in black locust & other trees. The smallest branches may lack discoloration.

Treatment: There is no cure for Japanese maple infected with Verticillium wilt, but healthy, established trees may survive with care, especially if only old wood is affected. Water deeply during droughts, apply slow-release fertilizer in spring, & regularly prune dead or damaged branches. Mulch to promote health & avoid mowing over the tree’s roots to prevent unnecessary injury. Remove severely infected trees & replace them with Verticillium-resistant species, such as conifers.