So many of our most interesting and useful tender crops and flowers are closely related and in the Solanum family. All the daturas and petunias, brunfelsias and nierembergias, cropping and sweet scented tobaccos, tomatoes and potatoes, peppers, physalis and aubergines, and even that oddly popular Goji berry.
I really cannot bring myself to recommend this last, it’s a lax shrub, effectively almost hardy, easy to grow and the fruit may be rich in vitamins and anthocyanins but so are rose hips and choke berries. Okay perhaps it deserves a place as a herb bed item but the Goji for me does not rate very highly as a tasty fruit. The Tree Tomato, Cyphomandra betacea, has large plum size crimson purple fruits almost resembling tomatoes and which can replace them in most savoury or even sweet dishes. This deserves a place in any frost free edible fruit collection. A small tree it can be easily grown in a big tub when it will be usefully cropping in winter under cover.
Another though more tender relative is even more tasty and that’s Solanum quitoense. I doubt if once you’ve ever seen this you can forget such an architectural plant. The large leaves and stems, dark green often with purple overtones, are strangely datura like but one on steroids. Then you notice the thorns sticking out over every surface and it starts to look more menacing. The flowers, recognisably potato like as with most solanums are not very showy, but are followed by spherical yellow balls most resembling fuzzy tomatoes and with a tart orange juice type flavour. And that is their use- for an orange juice like squash, and very tasty. Easy to grow from seed or slip these can quickly get quite large in a tub of ordinary compost. They only need to be kept warm and well fed and watered and when too big can be cut back hard, carefully.
Small specimens make delightful table plants and can be cropped later once bigger. Another interesting relative is Solanum muricatum, or Alligator pear, (so sometimes confused with an avocado) popular in warmer Mediterranean and Canary Island gardens this is a lax semi shrubby perennial, again undemanding as to conditions and with potato like flowers. And these turn into large green plum tomato come avocado shaped, often purple striped, fruits. These are remarkably similar to a succulent aubergine with a far more palatable taste and even the aroma of a melon though not getting quite as sweet. Well worth growing for the novelty.