Kousa Dogwood Problems

If you have a kousa dogwood in your garden, you know it’s a beautiful tree. But even these tough plants can have issues. Understanding common kousa dogwood problems is the first step to keeping your tree healthy. This guide will help you identify what’s wrong and show you how to fix it.

Kousa dogwoods are generally more resistant to disease than their cousin, the flowering dogwood. However, they are not immune. The issues they face often fall into a few key categories: environmental stress, pests, and a handful of specific diseases. Let’s look at the most frequent complaints.

Environmental and Cultural Stress

Many issues start not with a bug or fungus, but with the growing conditions. Getting these right prevents a lot of trouble.

Leaf Scorch and Drought Stress

You might see the edges of leaves turning brown and crispy. This is often leaf scorch. It happens when the tree loses water faster than its roots can absorb it. Hot, windy days make it worse.

Newly planted trees are especially vulnerable.
Soil that is too sandy or compacted can’t hold enough moisture.
A root system damaged by construction or digging struggles to drink.

Solution: Deep, infrequent watering is key. Give your tree a long soak once a week during dry spells, letting water penetrate the root zone. A 2-3 inch layer of mulch (like wood chips) spread out to the drip line helps retain soil moisture. Keep mulch away from the trunk itself.

Poor Flowering or Lack of Fruit

If your kousa isn’t blooming well or setting those pretty red fruits, don’t panic. This is rarely a sign of disease. Common causes include:

Age: Young trees may take several years to start blooming reliably.
Light: While they tolerate some shade, too much shade drastically reduces flowers.
Fertilizer: Too much nitrogen fertilizer pushes leaf growth at the expense of flowers.
Pruning: Pruning at the wrong time (like late summer) can remove the flower buds set for next year.

Solution: Ensure your tree gets at least a half-day of sun. Use a balanced, slow-release fertilizer in early spring, if needed. Prune right after the tree finishes blooming to avoid cutting off next year’s show.

Common Pests on Kousa Dogwood

While pests aren’t usually severe, a few bugs can cause noticeable damage.

Dogwood Borers

This is the most serious insect pest. The larvae tunnel into the trunk and branches, often near wounds or the base of the tree. Signs include:

Dying branches in the upper canopy.
Sawdust-like frass at the base of the tree or on bark.
Swollen, calloused areas on lower trunks where the tree has tried to heal.

Solution: Prevention is critical. Avoid damaging the bark with lawn mowers or trimmers. Keep the tree healthy and well-watered so it can resist attack. If you find borer holes, you can carefully probe them with a flexible wire to kill the larva. For bad infestations, a professional arborist may recommend a targeted insecticide treatment.

Scale Insects

These look like small, bumpy shells stuck to the twigs and branches. They suck sap, which can weaken the tree and cause leaves to yellow. A sticky substance called honeydew on leaves or under the tree is a telltale sign.

Solution: For light infestations, you can scrub branches with a soft brush and horticultural oil solution. Dormant oil sprays applied in late winter before bud break are very effective at smothering overwintering scales. Encourage natural predators like ladybugs.

Fungal and Disease Issues

Fungal diseases are less common in kousa than in flowering dogwood, but they can still occur, especially in wet, humid conditions.

Powdery Mildew

This fungus appears as a white, powdery coating on leaf surfaces. It’s more of a cosmetic issue than a life-threatening one, but it can be unsightly and cause some leaf curling or premature drop.

It thrives in warm days and cool nights with high humidity.
Poor air circulation makes the problem worse.

Solution: Choose resistant kousa cultivars if you live in a humid area. Prune to improve air flow through the canopy. Water at the base of the tree, not overhead. For severe cases, a fungicide containing potassium bicarbonate or neem oil can help.

Spot Anthracnose and Other Leaf Spots

Small, purple-bordered spots on leaves may be spot anthracnose or other fungal leaf spots. While disfiguring, these rarely threaten the overall health of an established kousa dogwood.

Solution: The best control is sanitation. Rake up and dispose of fallen leaves in autumn to remove the fungus. This prevents it from splashing back onto the tree in spring. Ensure good air circulation and avoid wetting the foliage when you water.

Canker Diseases

Cankers are sunken, dead areas on branches or the trunk. They are often caused by fungi that enter through wounds. The bark may be discolored and can peel back.

Solution: Prune out infected branches, making your cut several inches below the canker into healthy wood. Sterilize your pruning tools between cuts with a 10% bleach solution. The best defense is to keep the tree vigorous and avoid injuries to the bark.

Step-by-Step: Diagnosing Your Tree’s Problem

Follow these steps to figure out what’s going on.

Look at the Leaves: Are spots, powdery residue, or browned edges present? Are leaves yellowing between the veins or dropping early?
Check the Branches and Trunk: Scan for holes, oozing sap, cracked bark, or unusual bumps. Look for dieback at the tips of branches.
Examine the Base: Is mulch piled against the trunk? Are there mechanical wounds from lawn equipment? Do you see sawdust or borer holes?
Consider the Weather: Has it been exceptionally hot, dry, or wet? Did the problem appear suddenly after a specific event?
Review Your Care: Have you been watering deeply? When did you last fertilize or prune?

Prevention is the Best Medicine

A healthy tree resists problems much better than a stressed one. Here’s your prevention checklist:

Plant Properly: Choose a site with well-drained, slightly acidic soil and morning sun. Don’t plant to deep.
Water Wisely: Provide about 1 inch of water per week, more during droughts. Soak the entire root area.
Mulch Correctly: Apply a wide ring of mulch, but never let it touch the tree trunk (this can cause rot and invite borers).
Prune with Purpose: Remove dead, damaged, or crossing branches in late fall or winter. Sterilize tools.
Fertilize Lightly: If needed, use a balanced, slow-release fertilizer in early spring. A soil test can guide you.

FAQ: Quick Answers on Kousa Dogwood Care

Why are the leaves on my kousa dogwood turning yellow?
Yellow leaves can mean several things. If it’s the older, inner leaves, it might be a natural response to drought stress. If it’s new growth, it could indicate a soil pH issue (they prefer slightly acidic soil) or a nutrient deficiency, like iron.

Is it normal for kousa dogwood leaves to curl?
Some curling can occur during extreme heat to reduce water loss. However, significant curling along with a white powder points to powdery mildew. Aphids can also cause leaf distortion.

What should I do about moss or lichen on the trunk?
Moss and lichen are generally harmless. They often appear on mature, slow-growing bark. They are not causing the problem; they’re just taking advantage of a shady, moist surface. Focus on overall tree health instead.

My tree’s bark is peeling. Is that bad?
Kousa dogwoods have naturally exfoliating bark that peels in patches as they age, revealing a mottled tan and gray pattern underneath. This is a beautiful, normal characteristic! Only worry if the peeling reveals wet, sunken, or discolored wood beneath.

When is the best time to plant a kousa dogwood?
Early fall is ideal, giving the roots time to establish before winter and the heat of next summer. Spring planting is also fine, but you’ll need to be vigilant about watering through its first year.

With it’s graceful shape and long season of interest, a kousa dogwood is worth a little extra attention. By learning to recognize these common kousa dogwood problems early, you can take simple steps to correct them. Most often, the solution comes down to proper watering, smart planting, and good sanitation. Your tree will thank you with years of beauty.