Plant problems

Why Are My Ackee Leaves Curling?

Q: Is ackee safe to eat?

Ackee (Blighia sapida) must be eaten with great care: only the fully ripe, naturally opened fruit is safe, and only the creamy yellow arils (the fleshy parts attached to the base of the seeds) are edible. The unripe fruit, the red seed casings (pericarp), and the black seeds are all highly toxic. The toxin is hypoglycin A, a non-protein amino acid that inhibits fatty acid oxidation and causes severe hypoglycaemia (low blood sugar), vomiting, and convulsions in what is known as 'Jamaican vomiting sickness'; fatalities have occurred, particularly in children who ate unripe or improperly prepared ackee. The hypoglycin A content drops significantly as the fruit ripens and the pod opens naturally; the arils of a naturally opened, fully ripe ackee pod are safe to eat. In Jamaica, ackee is a staple food eaten daily; 'ackee and saltfish' is the Jamaican national dish, and Jamaicans are extremely familiar with the proper preparation of the fruit. Canned ackee (widely sold in the UK in Caribbean grocery shops and many supermarkets) has been heat-processed and tested; the canning process degrades the remaining hypoglycin A in the already-ripe arils, making the canned product safe. UK food regulations restrict the import of fresh ackee because of the food safety risk from improperly ripened fruit being present in shipments; most UK consumption is from canned ackee.

Q: Can I grow ackee in the UK?

Ackee (Blighia sapida) can be grown in the UK but only in a large, well-heated greenhouse or conservatory; it requires a minimum temperature of 15°C at all times and grows best above 20°C. It is a large tree in tropical conditions (reaching 15 metres) but in a UK greenhouse can be kept smaller by pruning and pot restriction, though it will still grow to 2 to 3 metres if given adequate space. Ackee is not a productive fruiting plant in UK greenhouse conditions; it rarely flowers or fruits because it needs tropical day length and heat consistently provided over many months. It is grown in the UK primarily as an ornamental specimen and cultural plant by Jamaican and Caribbean communities who value its connection to home. Growing ackee from seed requires fresh seed (the black seeds germinate readily when fresh but lose viability rapidly); sow immediately after obtaining fresh seed from a ripe, opened fruit, in a warm propagating environment (25 to 30°C). Young seedlings are sensitive to cold and low humidity; grow in well-draining tropical potting compost, water moderately, and maintain high humidity. Ackee is sometimes available as a young plant from specialist tropical plant nurseries in the UK, though it is not commonly offered.

Ackee (Blighia sapida) is a tropical tree from West Africa, naturalised in Jamaica where it is the national fruit and forms the basis of the national dish, ackee and saltfish. A heated UK greenhouse specimen of cultural significance to Caribbean communities in Britain, it requires temperatures above 15°C and rarely flowers or fruits in UK conditions. The large, pinnate leaves can curl when mealybug colonises the growing tips or when the greenhouse temperature drops too low in winter.

Mealybug

Mealybug (Planococcus citri and related species) is the most common pest of tropical trees in UK heated greenhouses, including ackee. The white, cottony colonies appear in the leaf axils, at the growing tips, and in the junctions between leaf stalks and stems; the insects extract sap continuously and produce copious honeydew that supports sooty mould. When mealybug colonises the young, unfolding leaves of ackee, the affected tissue curls and distorts during its development; this distortion persists even after the infestation is controlled. Heavy infestations weaken the tree significantly and can cause extensive leaf drop.

What to do

Dab colonies with methylated spirits on a cotton bud to kill adults on contact. Apply insecticidal soap or neem oil spray thoroughly to all plant surfaces, focusing on the leaf axils and growing tips, every 5 to 7 days for 3 to 4 weeks. Introduce Cryptolaemus montrouzieri (mealybug destroyer) or Leptomastix dactylopii (parasitoid wasp) for biological control in the greenhouse. Inspect weekly; populations rebuild rapidly in warm conditions. Quarantine new plants for 4 weeks before introducing them to the greenhouse.

Cold damage

Ackee requires minimum temperatures of 15°C and grows best above 20°C; temperatures below 12°C cause the leaves to pale, curl, and drop, and sustained cold below 10°C can damage the plant severely. In a UK heated greenhouse the principal risk is an overnight temperature failure in winter. Cold-damaged ackee drops its leaves; if the roots and main stem were not fatally chilled, the plant will recover and produce new growth when temperatures return to an adequate level.

What to do

Maintain temperatures above 15°C at all times. Use a minimum thermometer and a heating alarm to monitor overnight temperatures. In the event of a heating failure, move the tree to the warmest part of the greenhouse and insulate the pot with bubble wrap or fleece. Remove cold-damaged leaves and reduce watering until new growth appears; do not fertilise until the plant is actively growing again.

Scale insects

Soft scale (Coccus hesperidum) and other scale species can cluster on the stems, petioles, and leaf undersides of ackee in the UK greenhouse, producing honeydew and sooty mould. Affected leaves yellow and may curl. Scale can be difficult to detect until numbers are high because individual scales blend with bark texture; run a finger along the stems to feel the raised, waxy bumps of individual scales.

What to do

Scrub scale off stems with a stiff toothbrush and insecticidal soap solution. Apply insecticidal soap or neem oil spray to all plant surfaces, repeating every 10 days. Introduce Metaphycus helvolus for biological control of soft scale. Inspect stems and leaf undersides monthly; remove and treat localised outbreaks before they spread.

Low humidity

Ackee comes from the humid tropical forests of West Africa and requires moderate to high humidity; in the dry air of a heated UK greenhouse in winter, the large leaflets develop brown margins and curl. Low humidity also predisposes the plant to red spider mite. Maintaining 55 to 70% relative humidity in the greenhouse protects all tropical specimens including ackee.

What to do

Damp down the greenhouse floor and staging morning and early afternoon. Run a humidifier during the winter heating period. Mist the foliage gently in the morning; avoid misting in the evening to reduce fungal disease risk. Group tropical plants together to create a localised humid microclimate. A digital hygrometer confirms humidity levels accurately.

Frequently asked questions

Why are my ackee leaves curling?

Ackee (Blighia sapida) leaves curl most commonly in UK greenhouse conditions because of mealybug infestation, cold temperatures, scale insects, or low humidity. Mealybug appears as white cottony clusters in the leaf axils and growing tips; affected leaves curl and distort. Temperatures below 12°C cause leaf curl and drop. Scale insects produce honeydew and sooty mould on the stems and leaf undersides. Low winter greenhouse humidity causes leaf margin browning and curling.

Is ackee safe to eat?

Only the creamy yellow arils of a naturally opened, fully ripe ackee pod are safe to eat. The unripe fruit, red seed casings, and seeds contain hypoglycin A, which causes severe hypoglycaemia and vomiting (Jamaican vomiting sickness). Canned ackee sold in UK supermarkets and Caribbean shops is safe; the canning process degrades residual hypoglycin A. Fresh ackee imports to the UK are restricted for food safety reasons. Never eat ackee that has not naturally opened on the tree.

What does ackee taste like?

Ripe ackee arils have a rich, buttery, slightly nutty flavour with a creamy texture resembling scrambled egg; this is why ackee and saltfish resembles scrambled egg with smoked fish in both appearance and taste. The flavour is mild and savoury rather than sweet or fruity. Ackee is treated as a vegetable or egg substitute in Jamaican cooking rather than a fruit.

Can I grow ackee in the UK?

Only in a large, well-heated greenhouse or conservatory at a minimum of 15°C. Ackee grows very large in tropical conditions but can be kept smaller in a UK greenhouse by pruning and pot restriction. It rarely flowers or fruits in UK conditions. Grown primarily as an ornamental specimen and cultural plant by Caribbean communities. Can be grown from fresh seed at 25 to 30°C; young plants are sensitive to cold and low humidity.