What is sometimes called the thorned tomato is in fact the litchi tomato, Solanum sisymbriifolim, a member of the nightshade family. A close relative of the tomato and the potato, litchi tomato plants are covered by small thorns on both the stems and undersides of their leaves. Their dark red fruits, round and somewhat bullet-shaped, have yellow flesh.
The French botanist Michel Felix Dunal first reported the plant in the early 19th century after finding it in South America where it was used in local cuisine. He named it solanum balbisi in 1813; it was later renamed. It is sometimes called morelle de Balbis
The indented leaves of the litchi tomato resemble those of a true tomato. The plants grow from 3 to 4 feet tall, producing profuse, fluffy white flowers that look like those on an eggplant or potato vine. Litchi tomato vines can be caged like standard tomato plants.
Litchi tomato fruit droop in clusters. As the tomatoes ripen, their husks burst open. When a litchi tomato can be removed easily from the stem, it is ripe enough to eat. The fruits, about ½ inch in diameter, form inside husks like ground cherries or tomatillos; their seeds are arranged like that of a cherry tomatoes.
Litchi tomatoes are grown much like regular tomatoes. Start the seeds indoors in late February or early March. Put them into small pots and plant them outdoors when the danger of frost has passed. They grow into small bushes that require about 2½ feet between plants. You can put them into cages and prune them judiciously to produce more fruit. They like full sun, but can tolerate some shade; they can take frosts as low as 25degrees and develop woody stems that enable them to overwinter in protected areas where the ground does not freeze.
Disease and Insects
Litchi stems and leaves are rich in solasodine, a poisonous chemical that is used to make some varieties of contraceptive pills and steroids. While this makes the plant resist many diseases and pests, tomato worms will still attack it.
The opinion of those who have tasted litchi tomatoes is mixed. Some think the fruits are forgettable. Others think they can be usefully substituted for sour cherries in pies and also be made into preserves, jams and tarts.