Plant problems

Why Are My Goji Berry Leaves Curling?

Q: Why are my goji berry leaves curling?

Goji berry (Lycium barbarum), also called wolfberry, leaves curl most commonly in the UK because of aphid infestation, powdery mildew, or whitefly. Goji is a member of the Solanaceae family (related to tomato and potato) and shares some of the pest susceptibilities of those plants. Aphids, including the glasshouse and potato aphid (Aulacorthum solani) and peach-potato aphid (Myzus persicae), colonise the growing tips and undersides of the leaves in spring and summer, causing the leaves to curl and distort; the aphids are easy to overlook on the small, grey-green goji leaves. Powdery mildew (Erysiphe lycii) appears as a white or greyish powdery coating on the leaves and shoots in warm, dry conditions, causing the affected leaves to curl and distort. Whitefly (Trialeurodes vaporariorum) can colonise goji grown in greenhouses or in sheltered garden positions, clustering on the undersides of leaves and producing honeydew and sooty mould; infested leaves yellow and curl. Drought stress causes the leaves to wilt and curl inward at the margins.

Q: How do I grow goji berry in the UK?

Goji berry (Lycium barbarum) is well suited to UK garden cultivation and is one of the more straightforward exotic berries to grow here. It is fully frost-hardy (tolerating -15°C), deciduous, self-fertile, and extremely productive in a sunny position. Grow in any well-drained soil in full sun; goji is tolerant of poor, thin, alkaline soils and does not require rich conditions. It produces a vigorous, arching shrub to 2 metres that benefits from staking or tying to a wall or fence, as the arching canes can become unwieldy without support; it can also be grown as a loose, informal shrub. The small, white-purple flowers appear throughout summer and into autumn; the shiny, oblong, bright red or orange berries ripen from July onward. In good summers a single established goji plant can produce several kilograms of berries. Pruning is flexible: cut back hard in late winter to encourage vigorous new fruiting shoots, or trim lightly after fruiting. Goji is also easy to grow in a large container, which allows the arching canes to be trained and managed more precisely. The berries can be eaten fresh (they have a sweet, slightly bitter flavour and a texture like a ripe tomato) or dried.

Q: What are the health benefits of goji berries?

Goji berries (Lycium barbarum) have a long history of use in traditional Chinese medicine and have been widely marketed in the UK and elsewhere as a superfood for their antioxidant content, particularly zeaxanthin (a carotenoid important for eye health), beta-carotene, vitamin C, and polysaccharides. Research has investigated goji extracts and juice in relation to eye health (particularly age-related macular degeneration), immune function, blood glucose regulation, and antioxidant status. Some studies show promising results for zeaxanthin content and eye health specifically; the evidence base is stronger for this claim than for most other marketed health properties. The berries are a good source of vitamin C, fibre, and iron. As with most superfood health claims, many studies are small, short-term, or conducted with concentrated extracts rather than whole berries at realistic serving sizes; scepticism about extravagant marketing claims is warranted while the nutritional value of the berries as a whole food is genuine. Fresh UK-grown goji berries are nutritionally equivalent to the dried berries sold commercially; home-grown berries allow eating them fresh, which is unusual since almost all UK retail goji berries are sold dried.

Q: How do I control aphids on goji berry?

Aphids on goji berry in UK gardens, including the peach-potato aphid (Myzus persicae) and potato aphid (Aulacorthum solani), are most problematic in spring and early summer on the new growth. The small, grey-green goji leaves make aphids relatively easy to overlook until the infestation is established; check the undersides of the leaves on the growing tips weekly from April. To control: apply insecticidal soap or neem oil spray to the shoot tips and leaf undersides, repeating every 7 to 10 days; concentrate on the undersides of the young leaves. Encourage natural predators by avoiding broad-spectrum insecticides; ladybirds, lacewings, and hoverflies all feed on the aphid species that affect goji. A sticky residue of honeydew on the leaves below the infested tips is a reliable early warning sign; act at this stage before populations build. Heavily infested shoot tips can be pinched off and destroyed. Aphid populations on outdoor UK goji plants are generally self-limiting as natural predators establish; indoor or greenhouse plants may require more active intervention.

Goji berry (Lycium barbarum), also called wolfberry, is a hardy, productive shrub from China that is fully frost-tolerant and well suited to UK gardens. A member of the Solanaceae family (related to tomato and potato), it produces small, bright red or orange berries from midsummer onward, widely sold dried and marketed for their antioxidant content. It grows vigorously in most UK soils in a sunny position and requires minimal care. When the small, grey-green leaves curl, aphids on the growing tips are the most likely cause.

Aphids

Aphids are the most common cause of leaf curl on goji berry in UK gardens. The peach-potato aphid (Myzus persicae) and potato aphid (Aulacorthum solani), both of which are associated with the Solanaceae family to which goji belongs, colonise the undersides of the small, grey-green leaves and the growing tips from spring onward. Infested leaves curl and distort; the small size and grey-green colour of goji leaves make the pale green aphids easy to overlook until the infestation is well established. Honeydew dripping onto lower leaves and the presence of ants tending the colony are reliable early indicators.

What to do

Check leaf undersides and growing tips weekly from April. Apply insecticidal soap or neem oil to the shoot tips and leaf undersides, repeating every 7 to 10 days. Encourage ladybirds, lacewings, and hoverflies. Pinch off and destroy heavily infested shoot tips. Aphid populations on outdoor goji are generally controlled by natural predators without intervention; indoor or greenhouse plants may need more active management.

Powdery mildew

Powdery mildew (Erysiphe lycii) affects goji in warm, dry conditions with poor air circulation, appearing as a white or greyish powdery coating on the leaves and young shoots. Affected leaves curl and distort; in severe cases the young shoots are badly stunted. Mildew is more common on goji in sheltered positions against walls (where air circulation can be poor) and in dry summers. Goji appears moderately susceptible to powdery mildew; it is less commonly affected than some Solanaceae relatives but the problem can be significant in some years.

What to do

Improve air circulation around the plant by thinning the canes. Apply potassium bicarbonate or a sulphur-based fungicide spray at the first sign of infection, repeating every 10 to 14 days. Water consistently at the root to avoid drought stress, which increases susceptibility. Remove the most heavily infected leaves and shoots.

Whitefly

Glasshouse whitefly (Trialeurodes vaporariorum) can colonise goji grown in greenhouses or in very sheltered UK garden positions, clustering on the undersides of leaves. The tiny white adult flies scatter in a cloud when the plant is disturbed; the scale-like nymphs remain on the leaf undersides, producing honeydew and sooty mould. Infested leaves yellow and curl. Whitefly is primarily a problem on goji in greenhouse conditions; on outdoor UK plants it is much less common.

What to do

Introduce Encarsia formosa (a parasitoid wasp) for biological control of whitefly in greenhouses. Yellow sticky traps catch adults and help monitor population levels. Apply insecticidal soap or neem oil to the leaf undersides. Move plants outdoors in summer if possible; natural predators in the garden are more effective than any spray programme.

Drought stress

Goji is drought-tolerant in the ground but will show leaf wilt and marginal curl in a prolonged UK summer drought, particularly in containers or light, sandy soils. The leaves lose their usual slight glaucous colour and take on a yellowish-green cast before curling inward at the margins. Container-grown goji is significantly more vulnerable to drought than ground-planted specimens; the small pot volume can dry out completely within a day in hot weather.

What to do

Water container goji regularly throughout the growing season; do not allow the compost to dry out completely. Apply a mulch of bark or wood chip around the base of ground-planted goji to retain soil moisture in summer. Goji in the ground with normal UK rainfall rarely needs supplementary watering once established.

Frequently asked questions

Why are my goji berry leaves curling?

Goji berry (Lycium barbarum) leaves curl most commonly in the UK because of aphid infestation, powdery mildew, or whitefly. Aphids colonise the growing tips and leaf undersides from spring onward; the small, grey-green goji leaves make them easy to overlook. Powdery mildew appears as a white powdery coating in warm, dry conditions with poor air circulation. Whitefly is mainly a problem on greenhouse-grown plants. Drought stress causes the leaves to wilt and curl inward at the margins.

How do I grow goji berry in the UK?

Goji berry (Lycium barbarum) is fully frost-hardy, self-fertile, and productive in UK gardens. Grow in well-drained soil in full sun; it tolerates poor, alkaline soils. Support the arching canes against a wall, fence, or stake. The bright red or orange berries ripen from July onward; a single established plant can produce several kilograms in a good summer. Cut back hard in late winter to encourage vigorous fruiting shoots. Also easy to grow in a large container.

What are the health benefits of goji berries?

Goji berries contain zeaxanthin (important for eye health), beta-carotene, vitamin C, and polysaccharides. Research shows the strongest evidence for zeaxanthin content and eye health benefits. The berries are also a good source of vitamin C, fibre, and iron. Many commercial health claims are overstated; scepticism is warranted, but the nutritional value of the berries as a whole food is genuine. Home-grown fresh goji berries are nutritionally equivalent to the dried berries sold commercially.

How do I control aphids on goji berry?

Check leaf undersides and growing tips weekly from April. Apply insecticidal soap or neem oil to the shoot tips and leaf undersides, repeating every 7 to 10 days. Encourage natural predators by avoiding broad-spectrum insecticides. Pinch off and destroy heavily infested shoot tips. Aphid populations on outdoor goji are generally controlled by natural predators without intervention; greenhouse plants may need more active management.