How to Grow a Thai Sweet Tamarind Tree in a Tub on a Roof or Balcony

As city populations grow, tall buildings are taking over the open plots where people once planted a tree for pleasure. For many town dwellers, tubs on a roof, veranda or balcony have become the only way to grow flowers, fruit and vegetables. Alongside local fruits such as guava and lemon, many foreign fruit trees are now grown in tubs, and Thai sweet tamarind has become one of the most popular with rooftop gardeners. This report, published in March 2025, set out how to plant and look after the tree in a tub.

Tamarind, Tamarindus indica, is a tree of the legume family (Fabaceae). Bangladesh's Agricultural Information Service (AIS) says it originated in the savanna of Africa; in Bangladesh it is most common in Rangpur, Dinajpur, Thakurgaon, Bogura and Gazipur. Grown in the open, the tree can reach 25 to 30 metres. Its pulp turns sweeter and less sour as it ripens, and some sweet varieties have almost no acidity when ripe.

Where the local tamarind is very sour, the Thai type is sweet. In the horticulturist Julia Morton's account on Purdue University's NewCROP site, the sweet type grown in Thailand is known as 'Makham waan'. Besides Thailand, Indonesia, Myanmar and the Philippines have commercial tamarind plantations. Bangladesh has a sweet variety of its own: in 2009 the Bangladesh Agricultural Research Institute (BARI) released 'BARI Tetul-1', a sweet tamarind suited to the hill areas.

According to AIS, 100 grams of ripe tamarind contain 170 mg of calcium, 10.9 mg of iron and 64.4 g of carbohydrate.

The first rule for a tub is the right plant. AIS notes that a tamarind tree raised from seed starts bearing after seven to eight years, while a grafted tree bears in two to three. Rooftop growers therefore warn that a seedling in a tub simply wastes two or three years. Buy a grafted Thai sweet tamarind from a nursery and make sure of what you are getting: true grafts are somewhat hard to find, and judging the plant is up to the gardener. Morton records that tamarind is easily propagated by cuttings, shield-budding, side-veneer grafting or air-layering.

Loam or sandy loam is the ideal soil for Thai sweet tamarind. The steps are:

• Mix two parts loam or sandy loam with one part cow dung.
• Mix two parts loam or sandy loam with one part well-rotted cow dung. How much chemical fertiliser such as TSP and potash to add depends on the tub and the soil, so take the local upazila agriculture office's advice. Fill a large tub with the mix, water it and leave it for 10 to 12 days, then loosen the soil and leave it a few days more. Then plant a healthy grafted plant in the tub.
• Fill a large 20-inch tub with the mix, water it and leave it to stand.
• After 10 to 12 days, loosen the soil well and leave it for another four to five days.
• Then plant a healthy grafted plant in the tub.

The plant needs little special care in its first few months, but it must be watered enough and kept free of weeds. From six months after planting, give it rotted mustard oil cake water once a month, loosening the soil in the tub before each feed.

Thai sweet tamarind takes about seven months from flower to ripe fruit, and the tree fruits twice a year, first in the monsoon and again in winter. Insect attack is uncommon, but in the rainy season fungus can strike and make the fruit split. AIS likewise says tamarind is usually free of pests and disease but can be attacked by fungus in the monsoon. As a remedy, spray a good fungicide every 10 days starting before the rains arrive. Morton adds that heavy rain while the fruit is developing prevents bearing, and that elsewhere scale insects and mealybugs are the main pests of tamarind.

Photo: Jungle Rebel / Wikimedia Commons (CC BY-SA 3.0)

Sources: The Agro News (Staff Correspondent), Agricultural Information Service (AIS), Purdue University NewCROP (Julia Morton, Fruits of Warm Climates), Wikipedia