Corylopsis Leaves Curling
Powdery mildew and lime-induced chlorosis are the most common reasons corylopsis leaves curl. This guide shows you how to identify each cause and keep winter hazel vigorous and full of flower.
1. Powdery mildew
Powdery mildew is the most commonly seen foliage disease on corylopsis in UK gardens. The fungus thrives in warm, dry conditions and spreads rapidly on the large, soft leaves that corylopsis produces. Plants in sheltered, enclosed positions with restricted air movement are most at risk.
What to look for
A white or pale grey powdery coating develops on the upper surface of leaves, most obviously on the young growth at shoot tips. Affected leaves curl upward and inward and may appear slightly shrivelled or puckered at the margins. Heavy infections spread across the whole canopy by late summer, giving the plant a dusty, greyish appearance. The coating can be rubbed off with a finger, distinguishing it from the pale colour that lime-induced chlorosis produces.
What to do
Remove and bin affected shoot tips. Open up the canopy by removing crossing or overcrowded branches after flowering to improve air circulation. Avoid high-nitrogen feeds in late summer that encourage soft, susceptible new growth. Water at the base of the plant in the morning so foliage stays dry during the day. Spray with a diluted milk solution (one part whole milk to nine parts water) every two weeks from the first signs of infection. For persistent mildew, a sulphur-based or myclobutanil-based fungicide applied preventively from late spring provides reliable protection.
2. Lime-induced chlorosis (iron deficiency)
Corylopsis is a calcifuge genus native to woodland habitats in China, Japan, and the Himalayas, where acidic, humus-rich soils prevail. It needs a soil pH between roughly 5.5 and 6.5 to absorb iron and other micronutrients adequately. In alkaline or neutral soils, or where lime has been incorporated near the planting site, iron becomes chemically unavailable and the plant cannot green up its leaves normally.
What to look for
Yellowing appears between the leaf veins, which remain green, producing a distinctive netted or veined appearance. This interveinal chlorosis is most pronounced on the youngest leaves at the shoot tips, which are most actively growing and most dependent on micronutrient supply. Affected leaves may also curl slightly at the margins and feel slightly papery. In severe cases leaves turn almost entirely cream or pale yellow and growth slows markedly. The plant produces few or no flowers in the following season.
What to do
Test soil pH with a simple kit. If it is above 6.5, apply a sequestered iron chelate product as both a soil drench and a foliar spray in early spring and again in midsummer, following the manufacturer's instructions. This supplies iron in a form the plant can absorb regardless of soil pH. Mulch annually with acidic organic material such as pine bark or composted wood chip to gradually lower pH over several seasons. Apply ericaceous fertiliser in spring to support healthy growth. On strongly alkaline soils, the only long-term solution is to grow corylopsis in a large raised bed filled with ericaceous compost.
3. Vine weevil (Otiorhynchus sulcatus)
Corylopsis grown in containers is susceptible to vine weevil larval damage. The larvae feed on roots through autumn and winter, and by spring the plant may be severely weakened or dead. Container-grown specimens purchased from garden centres occasionally arrive with vine weevil larvae already present in the compost.
What to look for
Adult vine weevil beetles notch the margins of leaves at night, leaving characteristic irregular scalloped edges. This leaf damage alone is not serious. However, if the plant wilts, leaves curl, and the whole shrub declines despite watering, larval root damage is likely. Tip the plant out of its container and examine the compost for white, C-shaped grubs up to 10 mm long. In the ground, wilting without obvious cause in an otherwise healthy corylopsis warrants careful investigation of the roots.
What to do
Apply parasitic nematodes (Steinernema kraussei) to the compost or soil in late summer and early autumn when temperature is between 5 and 20 Celsius for effective biological control of larvae. For container plants, replace heavily infested compost and treat the new compost before repotting. Collect adult beetles by going out after dark with a torch; they shelter under pots, in compost, and in leaf litter during the day. Yellow sticky traps near the plant catch adults and provide an early warning of population build-up.
4. Drought stress
Corylopsis is a woodland plant that naturally grows in sheltered, moist, humus-rich environments. In a garden setting, particularly in an open, sunny position or in free-draining soil, it can suffer from drought stress during warm summers. Container specimens are especially vulnerable as their restricted root volume dries out quickly in hot weather.
What to look for
Leaves curl inward along the midrib and may take on a slightly dull, yellow-green tone rather than their usual fresh mid-green. In more severe drought the leaf margins and tips turn brown. Container plants may wilt visibly within a day or two of warm weather if not watered. Unlike mildew or chlorosis, drought curl typically affects the whole leaf uniformly rather than showing a localised pattern, and the plant recovers quickly once watered.
What to do
Water container corylopsis thoroughly every day or two during warm summer weather. Stand pots on feet to ensure drainage and consider moving them to a semi-shaded position during heatwaves. Mulch garden plants with a 100 mm layer of acidic organic material such as bark chip to conserve soil moisture and regulate soil temperature. Choose a planting position that receives dappled shade rather than full afternoon sun to reduce moisture demand. Water new plants deeply twice a week throughout their first two summers to help them establish.
5. Aphids
Corylopsis is related to witch hazel and can be attacked by some of the same aphid species. Aphid populations tend to build on the soft new growth in spring, causing the characteristic leaf curling that shelters the colony from both rain and predators.
What to look for
Young leaves at the growing tips curl tightly and appear crinkled or puckered. Part the curled tissue to find clusters of pale green, yellowish, or brownish aphids feeding on the undersides. Sticky honeydew on leaf surfaces below the colony leads to black sooty mould colonisation. Ants moving up and down the stems confirm an active aphid colony. Aphid populations peak in late spring and early summer, then typically decline as natural predators build up.
What to do
Knock small colonies off with a strong jet of water or squash them by hand. Spray persistent colonies with a horticultural soap solution, directing the spray inside curled leaves where the aphids are sheltered. Encourage natural predators by planting nectar-rich flowers nearby and avoiding broad-spectrum insecticides. On a healthy, established corylopsis, aphid damage is rarely serious enough to require chemical treatment; natural predators will generally resolve the population within a few weeks.
Frequently asked questions
Why are my corylopsis leaves turning yellow between the veins?
Interveinal yellowing (veins stay green while tissue between them turns yellow) on corylopsis almost always indicates lime-induced iron deficiency. Corylopsis is a calcifuge that needs acidic soil. If your soil pH is above 6.5, apply sequestered iron chelate as a soil drench and foliar spray in spring, and mulch with acidic organic material to gradually lower the pH.
Can corylopsis grow in alkaline soil?
Corylopsis struggles in alkaline or chalky soil because high pH locks up iron and other micronutrients it needs. In neutral to slightly alkaline soil, remediation with sequestered iron and acidic mulches can sustain a reasonable plant. On strongly alkaline chalk soil, it is better to grow corylopsis in a large raised bed of ericaceous compost or to choose a different genus.
Why did my corylopsis lose its flowers after a late frost?
Corylopsis flowers very early in the year (February to March) and the open flowers are killed by temperatures below about minus 2 Celsius. This is one of the main frustrations of growing early-flowering shrubs in the UK. Plant in a sheltered position out of frost pockets, and avoid north and east-facing aspects where late frosts linger longest.
How do I get my corylopsis to flower more freely?
Corylopsis flowers on wood produced the previous summer. Prune only lightly and immediately after flowering, removing weak or crossing stems rather than cutting back hard. Ensure the plant has adequate light; deep shade reduces flowering significantly. A mulch of acidic organic matter in spring and a top-dressing of ericaceous fertiliser supports the vigorous summer growth that carries next year's flower buds.
Why are my corylopsis leaves curling in summer?
Summer leaf curl on corylopsis without any white coating or yellowing is most likely drought stress. Although corylopsis is a woodland plant accustomed to sheltered, moist conditions, hot, dry summers can stress it significantly. Water regularly and mulch the root zone to keep the soil consistently moist. Container specimens need daily watering in warm weather.
Find the best spot for your plants
Plant Compass maps the sun path across your windows so you know exactly which plants will thrive in each spot before you buy. Coming soon to the App Store.
Learn more