Why Are My Elderberry Leaves Curling?

Black bean aphid

Black bean aphid (Aphis sambuci, also called elder aphid) is by far the most common reason for curled, distorted leaves on elderberry in the UK. Dense colonies of small, shiny black aphids pack the shoot tips, stem nodes, and leaf undersides from April onward, causing the leaflets to curl tightly downward and inward; heavily infested shoot tips collapse under the weight of the colony. The honeydew they produce drips onto lower leaves and supports sooty mould, giving the plant a blackened, greasy appearance. The visual impact is dramatic and alarming to first-time growers. However, elderberry is an exceptionally vigorous plant and recovers completely once aphid populations fall. By mid to late June, parasitoid wasps and hoverfly larvae typically devastate the colonies.

What to do

• Pinch off or prune the most heavily infested shoot tips in April before colonies build. Hose the plant down with a strong jet of water to dislodge aphids. Plant companion flowers (pot marigolds, phacelia) nearby to attract hoverflies and parasitoid wasps early in the season. Avoid insecticides during the flowering period (late May to June), when bees are visiting the flowers. Apply insecticidal soap only to the worst infestations, in the early morning when bee activity is low. By July, natural predators typically reduce the population without further intervention.

Elder leaf spot

Several fungal pathogens cause leaf spot on elder, including Cercospora depazeoides and Phyllosticta sambuci. These produce small, circular to irregular brown or dark spots on the leaflets; in wet summers the spots multiply and merge, causing the leaflet to yellow and curl at the margins before dropping. Elder leaf spot is rarely serious enough to significantly harm the plant given its vigorous growth rate, but a heavy infection on a young or stressed plant can cause premature defoliation.

What to do

• Collect and destroy fallen leaves in autumn. Improve air circulation by pruning the shrub to an open shape; elder responds well to hard pruning and can be cut back severely each spring if desired. Apply a copper-based fungicide in severe cases, though intervention is rarely necessary on established elder. Ensure the plant is not drought-stressed, as stressed plants are more susceptible to leaf spot.

Powdery mildew

Powdery mildew can affect elder in dry summers, appearing as a white, powdery coating on the young leaves and shoot tips, which may curl and distort. Ornamental elder cultivars with dark, cut foliage (such as 'Black Lace' and 'Black Beauty') can be more susceptible to mildew than the plain green species. Mildew on elder is rarely serious and is most commonly seen on plants in dry, sheltered positions with poor air circulation.

What to do

• Ensure consistent moisture at the roots. Improve air circulation by thinning congested stems. Remove infected shoot tips. Apply a potassium bicarbonate spray in severe cases. Hard pruning in late winter or early spring (cutting the shrub back hard produces vigorous new growth and reduces the amount of overwintering mildew inoculum on the stems).

General management

Elder is one of the most self-sufficient shrubs in the UK garden. It requires no feeding, tolerates most soil types, copes with both wet and dry conditions once established, and needs no formal pruning to remain healthy. For culinary elderberry production, some gardeners prune their elder hard each spring (to within 30 cm of the ground) to produce vigorous new growth with large flower and fruit clusters; this approach also removes overwintering pests and disease inoculum from the old stems. Hard-pruned elders do not flower or fruit in their first year back, so an annual crop requires pruning only one stem in three each year on a rotation.

Frequently asked questions

Why are my elderberry leaves curling?

Elderberry (Sambucus nigra) leaves curl most commonly in the UK because of black bean aphid (Aphis sambuci). Dense colonies of small, shiny black aphids pack the undersides and stem tips of elder in April and May, causing the leaflets to curl tightly downward and inward and the shoot tips to distort and collapse under the weight of the colony. The effect can look alarming on a heavily infested elder. However, elderberry is an extremely vigorous plant and recovers fully once aphid populations decline, which they typically do by July as parasitoid wasps and hoverfly larvae reduce their numbers.

How do I control black bean aphid on elderberry?

Black bean aphid on elderberry is best controlled by encouraging natural predators rather than by repeated insecticide applications. Pinch off or prune back the most heavily infested shoot tips in April and May before populations build. Hose the plant down with a strong jet of water to dislodge aphids. Plant nectar-rich companion plants near the elder to attract hoverflies and parasitoid wasps early in the season. If intervention is necessary, use insecticidal soap applied in the early morning when bee activity is low. By June or July, parasitoid wasp populations typically reduce the aphid infestation dramatically. Avoid insecticides during the flowering period (late May to June).

Is elderberry safe to eat?

Elderberries (Sambucus nigra) are safe to eat when cooked but should not be eaten raw. Raw elderberries, elderberry leaves, bark, and roots all contain cyanogenic glycosides that can cause nausea, vomiting, and diarrhoea. Cooking destroys these compounds and cooked elderberries are completely safe, widely used for jam, wine, cordials, and medicinal preparations. Elderflowers are safe and consumed in large quantities as elderflower cordial. The berries should be ripe (dark purple-black) before use; unripe green elderberries have a higher concentration of toxic compounds.

When do elderberries ripen in the UK?

Elderberries in the UK ripen from late August through September and into early October depending on cultivar and location. Wild elder typically ripens in August to September in the south and up to a month later in the north. The berries turn from green to red to deep purple-black when ripe and should be harvested when fully black and drooping. Harvest the entire flower head and strip berries from stems using a fork, as the stems should not be included in cooking. Cultivated varieties such as 'Black Beauty', 'Black Lace', and 'Haschberg' typically fruit more reliably and produce larger berry clusters than wild elder.