Why Are My Plantain Leaves Curling?

Banana bunchy top virus

Banana bunchy top virus (BBTV) is transmitted by the banana aphid (Pentalonia nigronervosa) and causes one of the most visually distinctive forms of leaf distortion in the Musa genus. Infected plants produce progressively narrower, more upright, and more brittle leaves as the virus builds up in the plant; the youngest emerging leaves curl at the margins and fail to unfurl to the normal broad, flat shape, giving the growing tip a bunched, compressed appearance. The veins of affected leaves show dark green streaks on a yellowing background. Infected plants are severely stunted and rarely fruit; the disease is ultimately fatal to productivity though the plant itself may survive for years in a declining state.

What to do

• Remove and destroy infected plants, including the corm and roots; BBTV can spread from the plant via sucker shoots even if the mother plant shows limited symptoms. Control banana aphid populations on healthy plants with insecticidal soap. Do not propagate offsets (pups) from infected plants. BBTV is a quarantine pest in many countries; report suspect plants to your local RHS helpline if you are unsure.

Sigatoka leaf spot

Sigatoka (yellow sigatoka, Mycosphaerella musicola, and black sigatoka, Mycosphaerella fijiensis) are fungal diseases that cause streaks and lesions on plantain and banana leaves. Yellow sigatoka causes pale yellow streaks that expand to brown or tan lesions with a yellow border; black sigatoka (the more damaging form) causes narrow brown streaks that expand rapidly to large, dead areas with a yellow halo. Heavily affected leaves die prematurely, curl, and collapse; severe infections can defoliate the plant and significantly reduce fruit yield. Sigatoka is favoured by warm, humid conditions and poor air circulation.

What to do

• Remove and destroy affected leaves. Improve air circulation and avoid overhead watering. A copper-based fungicide spray applied preventively in humid conditions can reduce spread. Ensure adequate spacing between plants. Sigatoka is a more significant problem in tropical commercial production than in UK greenhouse growing, but can occur under warm, humid glasshouse conditions.

Drought

Plantains are large plants with enormous leaf surface area; they lose water rapidly through transpiration and need consistent, generous watering during the growing season. In drought conditions or if watering is inadequate for the plant's size, the leaves roll inward along their length (like a scroll), reducing the exposed surface area to conserve water. This rolling is reversible and the leaves unfurl when water supply is restored, but prolonged drought causes the leaf edges to brown, dry, and remain curled even after rewatering.

What to do

• Water plantains very generously in spring and summer; large plants in containers in warm conditions may need daily watering. Apply a thick mulch to retain soil moisture in border-grown plants. In a very hot summer, temporary afternoon leaf rolling is normal in large plants even with adequate watering; this resolves by evening. Persistent morning rolling indicates chronic drought stress.

Cold damage

Plantains are not frost-hardy and are damaged by temperatures below 10°C. Cold causes the large leaves to yellow at the edges, develop brown patches, and curl as cell membranes are damaged. A single frost kills the pseudostem (the apparent trunk, which is in fact a tightly rolled stack of leaf bases) to the ground, though the underground corm may survive and regenerate if insulated. UK winters outdoors are too cold for most plantain cultivars without protection; the related but much hardier Musa basjoo can survive UK winters but is not an edible plantain.

What to do

• Bring container-grown plantains under glass before the first frost (typically October in most of the UK). In a heated greenhouse, maintain temperatures above 10°C through winter; reduce watering significantly when growth slows. For outdoor-grown plants, cut back the pseudostem to about 1 metre after frost kills the tops, apply a very deep mulch (30 to 45 cm) of straw or bark over the corm, and hope for a mild winter; this works reliably only in the mildest UK locations.

Frequently asked questions

Why are my plantain leaves curling?

Plantain (Musa x paradisiaca and related cooking banana cultivars) leaves curl most commonly because of banana bunchy top virus (BBTV), sigatoka leaf spot, drought, or cold temperatures. Banana bunchy top virus (BBTV), spread by the banana aphid (Pentalonia nigronervosa), causes the youngest leaves to emerge narrow, upright, and with wavy or curling margins rather than unfurling to the normal broad, flat leaf; as the name suggests, the growing tip appears bunched and the plant is severely stunted. Sigatoka causes yellow to brown streaks and lesions on the leaf surface that merge, causing premature leaf death and collapse; in severe cases the leaves curl and die back from the edges inward. Drought causes the large plantain leaves to roll upward and inward along their length as the plant reduces its exposed leaf surface to conserve water. Cold temperatures below 10°C cause the leaves to yellow, develop brown edges, and curl as the plant enters cold stress.

How do I grow plantains in the UK?

Plantains (cooking bananas, Musa x paradisiaca and related cultivars) can be grown in the UK as large container plants in a heated greenhouse, conservatory, or sheltered outdoor position in the warmest parts of the country during summer. Like ornamental and edible bananas, plantains need warmth (above 18°C for growth, above 25°C for fast growth), high humidity, rich soil, and consistent moisture to thrive. In the UK, plantains are unlikely to produce fruit unless grown in a very large heated greenhouse: the plants need a continuous warm growing season of 9 to 18 months to produce a flower and fruit cluster, which is difficult to achieve without heat supplementation in winter. However, the large, architectural leaves make plantains a spectacular summer patio plant in a sheltered spot, and the pseudostem can survive mild UK winters if the root is insulated with a deep mulch. Source plantains as pot-grown plants or offsets (pups) from the base of an existing plant rather than seed.

What is banana bunchy top virus?

Banana bunchy top virus (BBTV) is one of the most serious diseases of banana and plantain globally, causing severe stunting and distortion that renders infected plants non-productive. It is caused by a nanovirus and is transmitted persistently by the banana aphid (Pentalonia nigronervosa): once an aphid acquires the virus, it can transmit it for the rest of its life. Infected plants show a characteristic progression: the youngest emerging leaves are progressively narrower, more upright, and more brittle, with wavy or curling margins and a 'bunched' appearance at the growing tip; the older leaves become chlorotic (yellow) with dark green streaks along the veins. Infected plants rarely produce fruit and those that do produce small, distorted bunches. There is no cure; infected plants must be removed and destroyed, including the corm and roots. BBTV is a quarantine pest in many countries; in the UK it is not established but could theoretically be introduced on infected planting material.

Is plantain the same as banana?

Plantains and bananas are both members of the genus Musa and are closely related, but they differ primarily in culinary use and starch content rather than in botanical classification. The distinction between 'plantain' and 'banana' is cultural and culinary: in the tropics, 'plantain' usually refers to Musa cultivars that are starchy, less sweet, and typically cooked before eating (boiled, fried, or roasted), while 'banana' refers to sweeter cultivars eaten raw. In botanical terms, both are complex polyploid hybrids derived primarily from two wild species, Musa acuminata and Musa balbisiana. Plantain cultivars typically have a higher proportion of Musa balbisiana genetics, which contributes to their higher starch content and firmer texture. The large ornamental bananas (such as Musa basjoo, the hardy banana) grown in UK gardens are not edible plantains but a separate cold-hardy species; Musa basjoo can survive UK winters outdoors in mild areas, while edible plantains and bananas cannot.