Lonicera Leaves Curling

Honeysuckle aphid

Honeysuckle aphid is the single most damaging and recognisable pest on lonicera in UK gardens. Dense, pale waxy colonies of small, greyish-white or yellowish aphids cluster at the shoot tips and on the underside of the youngest leaves from spring onward, causing the leaves to curl tightly inward around the colonies and the shoot tips to become severely distorted. Unlike many aphid infestations where the insects are visible on exposed plant surfaces, the self-protective curling of lonicera leaves around honeysuckle aphid colonies makes the insects difficult to see until the damage is already substantial. Affected shoot tips look bunched, crumpled, and puckered, and the overall appearance of a heavily infested plant in early summer can be alarming. Honeydew deposits from the colonies encourage sooty mould development on the stems below, and heavily infested plants produce fewer flowers and look significantly less healthy through summer. The aphid populations can spread rapidly because the distorted, curled leaves shelter the insects from predators and from spray treatments.

Treat lonicera aphid infestations early, before the curling has progressed far enough to shelter the colony effectively. A strong jet of water from a hose directed at the shoot tips dislodges many of the insects and is most effective before the leaves have curled tightly. Follow up immediately with an insecticidal soap spray or a pyrethrin-based spray applied thoroughly to all affected growing points, working the nozzle into any curled leaves to reach the aphids inside. Repeat the treatment at five-day intervals for two to three applications. Cutting back the most severely distorted shoot tips removes the worst colonies outright. Because lonicera is an important nectar source for moths and butterflies, including the hummingbird hawk-moth, avoiding systemic neonicotinoid insecticides that persist in pollen and nectar is particularly important on this plant. Physical and contact-only treatments are both effective and appropriate for honeysuckle.

Powdery mildew

Powdery mildew is a very common problem on lonicera, particularly on plants trained against walls or fences where air circulation is limited and on established climbers with dense, crowded growth in the inner canopy. The disease appears from midsummer onward as a white or pale grey floury coating on the upper surfaces of the leaves, which curl at the margins as the infection spreads. Lower and inner leaves within a dense climber are typically affected first, and the symptoms spread outward and upward through the plant as the season progresses. The combination of warm days, cool nights, and the dry air close to a sheltered wall that is typical of late UK summers creates near-perfect conditions for mildew on lonicera. Plants that experience periods of moisture stress at the roots are particularly susceptible, as the stress weakens the plant's defences. Powdery mildew on lonicera is usually primarily cosmetic on an otherwise established, healthy plant, but severe and repeated infections weaken the plant over seasons and reduce flowering.

Improve air circulation within and around the lonicera by removing crowded, crossing, and inward-growing stems during the annual pruning after flowering. Thin the growth that presses closest to a wall or fence. Water consistently at the base throughout the growing season, particularly during dry spells, as moisture-stressed plants are most susceptible. Remove and bin affected leaves promptly. Spray with a potassium bicarbonate fungicide or bicarbonate of soda solution (one teaspoon per litre with a drop of dish soap) weekly from the first sign of white coating until the infection stops spreading. There is significant variation in mildew susceptibility between lonicera species and cultivars, and consistently affected plants may be worth replacing with a more resistant variety.

Drought

Drought stress causes lonicera leaves to curl inward and the plant to wilt, particularly on climbers trained against south or west-facing walls where reflected heat and dry air can be intense in summer. Plants against walls receive less natural rainfall than those in open positions because the wall creates a rain shadow, and the competition from wall footings and dry soil at the base of a fence makes the problem worse. Lonicera trained over a pergola or allowed to scramble freely through shrubs suffers less drought stress than those against walls because the roots access moisture from a wider area. Young plants in their first season are particularly vulnerable as their root systems have not yet developed to access moisture from depth.

Water lonicera at the base thoroughly during dry spells, especially plants trained against walls. Mulch annually with a thick layer of bark or garden compost, keeping it away from the main stems, to retain soil moisture. Incorporating organic matter at planting in the soil around wall-trained lonicera improves moisture retention significantly. Established lonicera with a deep, well-developed root system is surprisingly drought-tolerant in open positions, but wall-trained plants require consistent attention to soil moisture throughout their lives. A wilting lonicera that is otherwise healthy will recover rapidly once properly watered, with the leaves uncurling within hours of the moisture stress being relieved.

Scale insects

Scale insects occasionally colonise lonicera, with the flat, waxy, limpet-like insects clustering on the stems and on the undersides of leaves. Heavy scale infestations cause yellowing, premature leaf drop, and a general weakening of the plant. The honeydew secreted by the insects coats the leaves below the infestation and encourages sooty mould growth, which turns the leaves and stems black. Scale on lonicera is most common on plants in sheltered, warm positions and on those that have not been pruned to maintain open, well-ventilated growth. A moderate scale infestation on a healthy plant may go unnoticed until the black sooty mould on the foliage below the colony makes the problem obvious.

Treat light scale infestations on lonicera by physically wiping the insects off the stems with a damp cloth or by scrubbing with a soft brush and soapy water. Heavier infestations respond to horticultural oil spray applied to all stems and leaf undersides, which smothers the scale insects. Apply in late spring when the young crawlers are active and before they have developed their protective waxy coating. The annual pruning of lonicera, which removes older, heavily colonised stems and opens the plant to light and air, is one of the most effective long-term controls for scale.

Waterlogging

Waterlogging causes root rot in lonicera and produces above-ground symptoms of yellowing leaves, leaf curl, and general decline. Plants in heavy clay soils, in low-lying positions where water accumulates, or in containers without adequate drainage are most at risk. Lonicera planted immediately adjacent to a house wall, where drains and foundations can create waterlogged pockets, is also vulnerable. The symptoms of waterlogging closely resemble those of drought in early stages, as root damage in both cases limits water uptake, but the soil surface remaining wet and the presence of soft, discoloured roots distinguish waterlogging from moisture stress.

Plant lonicera in well-drained soil. In heavy clay or poorly draining soil, create a raised planting position and incorporate coarse grit at planting. Container lonicera should be in a free-draining potting mix with generous drainage holes and never left standing in water. If waterlogging has caused root rot, lift the plant, remove all rotted root tissue, allow the remaining healthy roots to air-dry briefly, and replant in a drier position with improved drainage. Established lonicera with a healthy root system is quite resilient once the drainage problem is resolved.

Vine weevil

Vine weevil grubs feed on lonicera roots over winter and autumn, causing the plant to produce weak, curling, yellowing growth in spring that collapses even in good conditions. Container lonicera is the most vulnerable because the grubs can access the root system easily within the confined soil volume. Adult vine weevils notch the leaf margins with semicircular cuts in summer, leaving characteristic C-shaped marks that confirm their presence. The notching itself does not cause the leaves to curl, but it is an important warning sign to check the root system for grubs before the winter feeding season begins.

Check container lonicera roots in autumn by removing the plant from its pot and examining the root ball for cream-coloured, C-shaped grubs. Apply nematode biological controls (Heterorhabditis bacteriophora) to the compost in late summer or early autumn when soil temperatures are above 10 degrees Celsius. Keep the compost moist for at least two weeks after application. Repot into fresh compost after treatment. In open ground, the vine weevil population is less concentrated and adult weevils are less likely to lay eggs in open, well-drained soil than in the moist compost of a container.

Frequently asked questions

Why are my lonicera leaves curling?

Honeysuckle aphid is by far the most common reason lonicera leaves curl, causing the shoot tips and young leaves to curl tightly around dense aphid colonies in spring and early summer. Powdery mildew causes white coating and leaf margin curling in late summer. Drought stress causes the whole plant to curl and wilt in dry conditions.

Does honeysuckle get aphids?

Yes, lonicera is one of the most aphid-prone climbing plants in UK gardens. Honeysuckle aphid colonies form dense, waxy clusters at the shoot tips and cause severe curling and distortion of the youngest leaves. The curled leaves shelter the aphids effectively and can make the infestation difficult to treat once established. Early intervention with a jet of water or insecticidal soap is most effective.

Why are my honeysuckle leaves turning yellow and curling?

Yellowing combined with curling on lonicera most often indicates powdery mildew in late summer or drought stress in hot, dry conditions. Heavy aphid infestations can also cause yellowing as the insects deplete the sap from the youngest growth. If the yellowing is on older, lower leaves with green new growth above, it may simply be natural shedding of the oldest foliage, which is normal on lonicera in late summer.

Can honeysuckle get powdery mildew?

Yes, powdery mildew is a very common problem on lonicera, particularly in late summer when warm days and cool nights create ideal conditions for the fungus. It appears as a white floury coating on the upper leaf surfaces and causes leaf margin curling. Improve air circulation by thinning overcrowded growth, water at the base, and spray with a potassium bicarbonate solution at the first sign.