Fans of Thai green curry (like myself) would be familiar with firm, pea-like fruits that are one of the ingredients of the savoury dish. Those fruits are produced by a plant that is botanically known as Solanum torvum, which is a relative of the common tomato and eggplant where all belong to the Solanaceae family. The plant is known via a range of common names which include devil’s fig, prickly nightshade, wild eggplant, turkey berry and pea eggplant.
Native to the Antilles, Solanum torvum is a slightly hairy but spiny, perennial plant, which adopts a shrubby growth habit. The plant can grow up to 3 m tall and features leaves that resemble those found on the eggplant (S. melongena). Flowers are produced in clusters and each blossom is white, in contrast those which are yellow produced by the tomato or violet by the eggplant. Fruits are small round berries which harvested for food in the immature stage when they are firm and green. Besides Thai cuisine, they are also used in Lao and Indian cuisines. When ripe, the fruits turn yellow.
It is also grown as a medicinal plant where the roots are traditionally used for poulticing cracks in the feet and seeds for the treatment of toothache in Malaysia. In Vietnam, the leaves are used to treat insomia and menstrual disorders. Extracts of the plant are used in India as an antidote for snakebite and insect stings and fruits are eaten to relieve stomachache. The fruits and leaves of this plant yield a steriodal alkaloid, solasodine, which is a precursor used for the manufacture of oral contraceptives.
Solanum torvum is a weed in tropical areas where it is common to find it in disturbed areas such as wastelands and construction sites. Birds which consume the fruits help to spread the seeds. It can also be introduced to new areas via equipment or transfer of contaminated soil. This plant is not usually available for sale in local nurseries and packeted seeds are also hard to come by (I have only come across a nursery selling its seeds in packets imported from Thailand). Since it is a food plant, I have been wanting to introduce this plant to the Fruit and Vegetable Garden in HortPark but before I got to do so, two individuals appeared miraculously between the fruit trees in theme garden!
Besides useful being a source of food and medicine, this plant is valuable as a rootstock source to confer resistance towards bacterial and verticillium wilts in economic solanaceous crops such as tomato, eggplant and naranjilla. Grafted plants are said to be more vigorous and able to tolerate diseases affecting the root system.
As mentioned before, Solanum torvum can be grown from seeds but new plants can also be raised from stem-cuttings. If more than one plant are grown, they should be spaced about 2 m apart. They thrive in a sunny spot that is well-drained and fertile. It is rather drought-tolerant and relatively free from pests and diseases but may succumb to attack by soil nematodes. Note that heavy rainfall will affect fruit set adversely.