Why Are My Dogwood Leaves Curling and What To Do?

Curling dogwood leaves are usually a sign of summer stress. Most of the time the tree is responding to heat and dry soil, not dying. The same curled look can also come from a fungus, insects in the trunk, or weedkiller drift, so what you see beside the curl matters more than the curl itself. The fix depends on the cause, and in many yards the first step is simply better watering.

Heat and Dry Soil Are the Most Common Cause

Dogwoods often curl their leaves across the whole canopy during hot or dry weather.1Journal of Environmental Horticulture. Leaf Curl and Water Relations of Kousa Dogwoods Showing Resistance to Summer Stress One of a plant’s first responses to drought is closing the tiny pores on its leaves that let water escape.2Acta Ecologica Sinica. Physiological and growth responses of two dogwoods to short-term drought stress and re-watering That saves water, but it also slows the tree’s food-making.3Acta Ecologica Sinica. Physiological and growth responses of two dogwoods to short-term drought stress and re-watering Curling adds a second layer of defense by shrinking the leaf surface facing the sun, which limits scorch.4Vander Giessen Nursery, Inc.. Q&A: Dogwood Leaf Curl

In a yard, this kind of curl shows up all over the tree rather than on one branch. It appears during or after a hot or dry spell, often by midsummer. The leaves usually stay green and free of spots or powder, and they often look worse in the afternoon heat and flatter by morning. Curl that relaxes by morning suggests the tree is still recovering on its own, while curl that stays tight day and night can point to a deeper or longer-running water shortfall, though other causes below can do this too.

Dogwoods are especially prone because they are naturally understory trees, used to shade from taller neighbors. Their roots are shallow and dry out fast in summer. Trees in full sun, near pavement, or out in the lawn feel the stress most. Hot wind and reflected heat from a driveway or house wall make water loss worse than the air temperature suggests, so one side of the tree may look worse than the other. A tree can even curl after a dry stretch when rain fell recently, because a light shower often wets only the surface and never reaches the roots.

Some trees handle all this better than others. Some kousa dogwoods curl much less than others through summer, so how much curl you see depends partly on your particular tree, not only the weather.5Journal of Environmental Horticulture. Leaf Curl and Water Relations of Kousa Dogwoods Showing Resistance to Summer Stress

A short bout of curl is a normal coping response, not damage. Long or repeated drought is different: it slows growth because food-making drops. Edges that turn brown and crispy are a sign the stress went too far.

How to Water and Mulch a Curling Dogwood

Deep watering is the main fix. Soak the ground under the canopy slowly, using a soaker hose laid in loose loops or a hose set to a slow trickle, so the water sinks in instead of running off. Aim to wet the top 6 to 12 inches of soil, where most roots are. For many yards that means an hour or more, though the time varies with soil type. Push a trowel or finger into the soil a day later. If it is damp at that depth, you watered enough; if it is dry, run it longer next time. Early morning is the best time, since less is lost to evaporation and the leaves are dry by evening.

In dry weather, water about once a week rather than a little every day. A daily sprinkle wets only the top inch, which dries quickly and encourages roots to stay shallow. If rain has soaked the ground, skip a watering. The test is soil moisture, not the calendar.

Mulch helps the soil hold what you give it. Arborist wood chips make a good mulch because their mixed sizes let water and air reach the soil.6ask.extension.org. Dogwood leaf curl, cause/cure #796953 Spread 2 to 3 inches out toward the edge of the canopy, and keep it a few inches away from the trunk to prevent rot. Replacing lawn grass under the tree also cuts competition for water.

Soil structure matters as much as moisture. Packed-down soil is a major reason yard and street trees struggle, because roots can’t spread in it.7Acta Horticulturae. GETTING TO THE ROOT OF TREE STRESS ALONG HIGHWAYS© Keep foot traffic, parked cars and heavy equipment off the area under the canopy.

A few habits make curling worse. Overwatering into soggy soil starves roots of air and also curls leaves. Fertilizing a stressed tree pushes growth it can’t support. And leaves that are already curled will probably stay curled, so judge your results by new growth and by how the tree handles the next hot spell.

Powdery Mildew Curls Leaves Under a White Coating

Powdery mildew is a fungus that leaves a white, dusty coating on dogwood leaves. The coating builds up on new growth and twists and curls the youngest leaves.8University of Kentucky College of Agriculture. Dogwood Powdery Mildew Later in the season, leaf tips and edges can look scorched, cupped and drooping, and badly hit leaves drop early.9University of Kentucky College of Agriculture. Dogwood Powdery Mildew

That’s why it gets mistaken for drought. By midsummer, infected leaves can be stunted, reddened and curled or puckered, so affected trees look thirsty even when they’ve had plenty of water.10Virginia Cooperative Extension. Foliar Diseases of Dogwood Mildew doesn’t need wet leaves the way many fungi do, so it can thrive even in dry weather.

You can check in a few minutes. Rub a curled leaf gently with a fingertip: mildew smears off like flour, while a dull or dusty-looking healthy leaf will not. Start with the newest leaves at the tips of branches, since mildew shows up there first. Early coatings can be thin and faint, so tilt the leaf in good light and look across its surface rather than straight down. On a well-watered tree, curled leaves tinted red or purple are one clue that mildew may be starting, but look for the powder to confirm it. And if watering doesn’t ease the curl over a couple of weeks while powder or tinting is present, treat it as a disease problem.

The native flowering dogwood is the type most often hit hard. Kousa dogwoods usually get little or none. Humid weather with shade and still air favors the fungus.

Treating and Preventing Powdery Mildew

Fungicide sprays work best when started before symptoms show or at the first sign of mildew.11Pacific Northwest Pest Management Handbooks. Dogwood (Cornus spp.)-Powdery Mildew Few products clear an infection that’s already established, so timing matters.12Pacific Northwest Pest Management Handbooks. Dogwood (Cornus spp.)-Powdery Mildew Spray every 7 to 14 days, closer together when the weather is humid.13Pacific Northwest Pest Management Handbooks. Dogwood (Cornus spp.)-Powdery Mildew Weekly sprays of potassium bicarbonate controlled mildew about as well as standard fungicides.14Canadian Journal of Plant Science. Management of powdery mildew in flowering dogwood in the field with biorational and conventional fungicides Swapping in a standard fungicide like propiconazole every fourth spray improved control.15Canadian Journal of Plant Science. Management of powdery mildew in flowering dogwood in the field with biorational and conventional fungicides Some dish soaps used as sprays can burn dogwood leaves, though.16Canadian Journal of Plant Science. Management of powdery mildew in flowering dogwood in the field with biorational and conventional fungicides Always follow the label, and spray in cool weather to avoid leaf burn.

Whether to spray at all depends on the tree. A mature tree with light mildew showing only late in summer usually survives without any spraying. Spraying matters more for young trees or ones hit badly year after year.

Air flow and site choice cut the fungus’s chances. Remove and dispose of diseased branches, and prune to open the tree to air.17University of Connecticut Extension. The Dogwood Decline Do that thinning each year after the leaves fall.18Gardening Help FAQs. Gardening Help FAQs Avoid crowding, heavy high-nitrogen fertilizer, and deep-shade or wet planting spots.19University of Connecticut Extension. The Dogwood Decline

When planting, resistance is the best protection. Most kousa dogwood varieties are highly resistant to powdery mildew, while most flowering dogwoods are highly susceptible.20Journal of Arboriculture. Disease Resistance in Dogwoods (Cornus spp.) to Foliar Pathogens There are exceptions: the kousa variety ‘Square Dance’ got as much mildew as flowering dogwoods.21Plant Disease Management Reports. Disease resistance of kousa, hybrid and flowering dogwood cultivar to diseases compared Hybrids of kousa and flowering dogwood, such as ‘Starlight’ and ‘Venus’, showed only light to moderate mildew.22Plant Disease Management Reports. Disease resistance of kousa, hybrid and flowering dogwood cultivar to diseases compared Ask the nursery for mildew-resistant flowering dogwood or kousa types, and check the tag for the variety name, not just “dogwood.”

Borers Inside the Trunk Can Curl Leaves Too

The dogwood borer is a moth whose larvae tunnel under the bark. That tunneling damages the trunk’s water pipes. Stems of an infested tree carried only 61 to 78% as much water as a healthy one, and its leaves stayed curled even when given plenty of water.23Annals of Applied Biology. Physiological responses of dogwood (Cornus florida) to infestation by the dogwood borer (Thamnosphecia scitula) The damage can also speed leaf aging, slow growth, and shrink and reshape leaves.24Annals of Applied Biology. Physiological responses of dogwood (Cornus florida) to infestation by the dogwood borer (Thamnosphecia scitula)

Look near the base of the trunk and at old wounds for rough, cracked or wet-looking bark. Sawdust-like material at holes or bark cracks suggests larvae are working underneath. Dieback of branches on one side fits the pattern of trunk damage cutting off water. Curl that doesn’t ease after deep watering is another clue, though it alone doesn’t prove borers.

Borers enter mainly through wounds from mowers and string trimmers, so a mulch ring that keeps equipment away from the trunk is the first defense. Regular watering keeps trees vigorous, which matters because stressed trees attract borers. A certified arborist can confirm the problem and advise on treatment.

Weedkiller Drift Twists New Leaves

Common broadleaf weedkillers 2,4-D and dicamba were tested on dogwood at drift-level doses as low as 1/200th of the label rate.25Weed Technology. Investigations of the sensitivity of ornamental, fruit, and nut plant species to driftable rates of 2,4-D and dicamba Leaf malformation was one of the main injuries measured.26Weed Technology. Investigations of the sensitivity of ornamental, fruit, and nut plant species to driftable rates of 2,4-D and dicamba These chemicals are in many lawn weed-and-feed products, so a treated lawn nearby, yours or a neighbor’s, can be the source.

The look is different from heat curl. New leaves cup, twist or grow narrow and strap-like, rather than the whole canopy rolling in the heat. Damage appears days to weeks after you or a neighbor sprayed, so think back over recent weeks. It is often worst on the side facing the sprayed area.

Avoid spraying on windy or hot days near trees, and don’t use weed-and-feed over the dogwood’s roots. Mildly affected trees usually grow normal leaves later, so water and wait.

How to Tell What’s Curling Your Dogwood

Look at the whole tree and at several leaves, because one odd leaf can mislead. The nutrient problems differ from curling, and a soil test is the reliable way to confirm them before you add anything.

Your county extension office can look at photos or a sample. Call an arborist if branches die back or bark is damaged. Combined causes are common, such as drought making borers worse, so more than one fix may be needed.