Why Are My Tamarind Leaves Curling?

Scale insects

Soft scale (Coccus hesperidum) is the most common pest of tamarind in UK greenhouse conditions. The insects appear as flat, oval, pale brown or greenish bumps on the undersides of the leaflets and on the stems; their feeding extracts sap and produces copious honeydew that drips onto lower leaves, supporting sooty mould growth. Infested leaflets curl, yellow, and drop; heavily infested branches decline progressively. Scale is difficult to detect until populations are established, as the insects are well camouflaged against the green and brown plant surfaces.

What to do

• Scrub scale off stems and leaflets with a soft toothbrush dipped in insecticidal soap. Apply a horticultural oil spray (neem oil) to the plant, paying attention to the undersides of the leaflets and the stem junctions. Introduce the parasitoid wasp Metaphycus helvolus for biological control in a heated glasshouse. Wipe sooty mould from leaves with a damp cloth once the scale population is controlled.

Low humidity

Tamarind is from seasonally dry tropical climates and tolerates low humidity better than many tropical plants, but in the extremely dry conditions of a UK home heated by central heating in winter, the small leaflets begin to curl inward and the leaf tips may dry and brown. Note that the normal nightly folding of tamarind leaflets (nyctinasty) is not a humidity problem; the folding should reverse fully in daylight. If the leaflets remain partly curled during the day, or if leaf tips are browning, low humidity may be a contributing factor.

What to do

• Place the pot on a wide gravel tray filled with water to increase local humidity. Mist the foliage with rainwater or distilled water in the mornings. Keep the plant away from radiators and heat vents. In a greenhouse, damp down the floor and staging to raise ambient humidity. Move to a more humid position such as a conservatory if growing indoors in winter.

Root rot

Tamarind is adapted to a seasonal tropical climate with a pronounced dry season and is more drought-tolerant than most tropical fruit trees; it does not tolerate persistently wet compost. Root rot (Phytophthora or Pythium) causes the leaflets to yellow and the compound leaves to droop and curl before dropping; the compost may smell sour and the roots will be brown or mushy rather than cream-coloured and firm. Root rot is common in UK cultivation when growers water tamarind on the same schedule as less drought-tolerant tropical plants.

What to do

• Allow the compost to partially dry between waterings; tamarind should be treated more like a drought-tolerant shrub than a moisture-loving tropical. Check soil moisture 10 cm deep before watering. In winter, reduce watering significantly; in a cool greenhouse (10 to 15°C), tamarind may need watering only once every 3 to 4 weeks. Repot into a free-draining mix (50% compost, 50% perlite or grit) if root rot is established.

Cold damage

Tamarind is a tropical tree with no significant cold tolerance. Temperatures below 10°C cause the leaflets to yellow at the margins, curl, and begin to drop; temperatures below 5°C cause lasting damage to the leaves and growing tips. In UK conditions, tamarind should be kept above 12°C in winter and in a full-sun position; even brief exposure to cold draughts near vents or glass in winter can cause localised leaf damage.

What to do

• Maintain temperatures above 12°C at all times. Reduce watering in winter. Keep the plant away from cold glass panes and draughty vents. Cold-damaged leaves do not recover but the plant will produce new growth as temperatures rise in spring. Tamarind is deciduous in its native range during the dry season; some leaf drop in winter in UK conditions is normal if growth slows and temperatures drop.

Frequently asked questions

Why are my tamarind leaves curling?

Tamarind (Tamarindus indica) leaves curl most commonly in UK greenhouse cultivation because of scale insects, low humidity, overwatering and root rot, or cold temperatures. Scale insects colonise the undersides of the leaflets and on the stems, producing sticky honeydew and sooty mould; infested leaflets curl, yellow, and drop. Low humidity in heated UK homes and greenhouses causes the leaflets to curl inward. Overwatering and root rot cause the leaflets to yellow and the whole compound leaf to droop and curl before dropping. Cold temperatures below 10°C cause the leaf margins to yellow and the leaflets to curl. Note that tamarind leaflets fold together at night (nyctinasty); this is normal behaviour, not stress.

Can I grow tamarind in the UK?

Tamarind (Tamarindus indica) can be grown in the UK as a heated greenhouse or large conservatory plant. It is most commonly grown from seed soaked overnight in warm water and sown at 25 to 30°C. Tamarind requires temperatures above 15°C, full sun, and well-drained compost. It is drought-tolerant once established and should be watered less frequently than most tropical plants. The attractive pinnate leaves with their nightly folding movement make tamarind a rewarding greenhouse specimen even without fruit; fruiting requires sustained high temperatures that are difficult to achieve in UK conditions.

Why do tamarind leaves fold up at night?

Tamarind leaves fold up at night in a phenomenon called nyctinasty (sleep movement). The paired leaflets on each tamarind leaf fold upward and together along the central midrib at nightfall and reopen in the morning. This movement is controlled by motor cells at the base of each leaflet, driven by changes in turgor pressure triggered by changing light. Nyctinasty is completely normal in tamarind and in many other members of the legume family. If the leaves remain closed or drooping during daylight hours, however, this indicates stress from overwatering, underwatering, very low light, or cold.

How do I grow tamarind from seed?

Tamarind seed germinates readily from fresh or properly stored seeds. Source seeds from fresh tamarind pods or from a reputable seed supplier. Soak the seeds overnight in warm water, or lightly nick the hard outer seed coat with a file to aid water absorption. Sow 1 to 2 cm deep in free-draining seed compost; keep at 25 to 30°C. Germination typically takes 1 to 3 weeks. Pot on as the seedling grows into a free-draining compost and perlite mix. Note that seeds from processed tamarind products (blocks or pastes) may not be viable; use seeds from fresh pods or a seed supplier for best results.