Tamarind

Identification and origin

Tamarindus indica belongs to the Fabaceae, the pea and acacia family. Its exact origin is still debated: the reference botanical checklist treats it as native only to Madagascar and the Comoros, while other references place it in tropical Africa, where it grows wild throughout Sudan. It has been grown in India for so long that it is often thought to be native there. Today it is planted throughout the tropics and subtropics.

In the ground, in a tropical climate, it is a large, slow-growing, very long-lived tree, 40–65 ft tall, that can reach 78.5–98.5 ft and spread 40–50 ft. Its dense, broad, rounded crown carries supple branches that droop at the ends. It is remarkably wind-resistant. The bark, gray-brown to blackish, is rough and fissured.

The evergreen foliage consists of compound leaves 3–6 in long, with no terminal leaflet, bearing ten to twenty pairs of oblong leaflets 0–1 in long and 0–0 in wide. Their special trait: the leaflets fold up at night. In very dry regions, the tree can briefly drop its leaves during the hot season.

From late spring into summer, small hanging clusters carry flowers about 1 in across, pale yellow with red or orange veins, opening from pink buds. The fruits are slightly curved, lumpy pods 2–7 in long that do not split open on their own. Velvety and brown when ripe, they hold a sticky, sweet-sour brown pulp around one to twelve glossy brown seeds. There are sweet types, such as ‘Makham Waan’ from Thailand or ‘Manila Sweet’, as well as red-fleshed forms.

Light

Tamarind loves full sun. In a container in a temperate climate, give it the brightest spot in the house, next to a well-lit window, and shield it from scorching midday sun through glass, which can burn the leaflets. It benefits from spending the warm season outdoors, in full sun after gradual acclimation.

Watering

Once well established in the ground, it handles drought very well. It does not tolerate waterlogged soil, though. In a container, water thoroughly when the top 1 in of mix is dry, until water runs out of the drainage holes, then empty the saucer. Its needs rise with sun and heat and drop markedly in a cool room in winter: always feel the mix before watering.

Potting mix

It is not fussy: it grows in clay, loam, or sand, acidic or alkaline, and even thrives in poor soils, provided they drain well. It does best in moist, fertile, sandy soil. In a container, choose a mix that drains well and never stays soggy. It tolerates salt poorly: near the sea, salt spray and salt around the roots damage it.

Temperature

It is a frost-tender tree that can only be grown in the ground in frost-free areas, in USDA zones 10a to 11b. Young trees must always be protected from cold. Older trees are tougher: one survived 27 °F for several hours, and a tree damaged by frost can resprout from its roots. In a container, keep it between 59 °F and 84 °F, away from air currents and sudden temperature swings, and bring it indoors before nights drop below 59 °F.

Repotting

In a container, repot every two to three years in early spring, before new growth starts. A young plant forms a taproot: choose a fairly deep pot and trim the roots moderately. During the growing season, from spring through autumn, apply a balanced fertilizer every two to four weeks, then stop in winter. In the ground, three feedings a year are enough: in early spring, midsummer, and early autumn.

Pruning

A young tree needs training: select three to five well-spaced main branches along a central trunk for a strong structure. In a container, regular pruning with clean, sharp tools keeps the shape compact and removes dead, diseased, or crowded wood.

Propagation

Seed is easy: seeds stay viable for months and germinate about a week after sowing. With water and good weeding, a seedling reaches 2 ft in its first year and 4 ft in its second. A seed-grown tree takes four to five years to flower and fruit, and its fruit quality is unpredictable. To reproduce a variety, growers use cuttings, air layering, grafting, or shield budding. Semi-hardwood cuttings root with warmth and humidity.

Common problems

A healthy tree has few serious problems. Leaf drop or decline can still have several causes: overwatering, cold, too little light, or pests. Look at the whole plant before acting.

• Scale and mealybugs: they can cause leaves and young fruit to drop.
• Aphids, whiteflies, thrips, and spider mites: they weaken the foliage; their honeydew encourages sooty mold, a black coating on the leaves. Insecticidal soap or horticultural oil helps control them.
• Root rot: it develops in a mix that stays soggy.
• Leaf spot: good air circulation limits it.
• Fruit: weevils bore into the seeds, and several days of rain on ripening pods cause rot.

Toxicity

Tamarind pulp is safely eaten by people, but it is toxic to dogs. It is very rich in tartaric acid, a substance that is toxic to dogs’ kidneys: vomiting and acute kidney injury have been seen after dogs ate tamarind. Cream of tartar, a form of the same acid, has caused the same problems. Keep tamarind paste and pods out of their reach, and contact a veterinarian promptly if your dog eats some.