(Solanum pseudocapsicum, syn. S. capsicastrum)
No, it’s not a cherry (Prunus), but a member of the Solanaceae (tomato) family. This beautiful plant from South and Central America is often offered as gift plant during the fall and winter months, when it is covered with attractive orange-red berries. The fruits can last almost all winter, but when they do fall off, the plant tends to deteriorate. This is less true where it is grown outdoors year round (in zones 9-12): under those conditions, it survives several years to become a small shrub (and—warning!—can even prove invasive!). When grown as a houseplant, though, it is often in poor shape by spring. In this case,
It’s usually easier to start new plants from seed than to try and maintain the original plant. Just harvest a few seeds from mature fruits and sow them indoors in mid-spring, exactly like you would start tomato or pepper plants (they’re very close relatives) and they’ll be in bloom by next winter.
If you want to keep the original plant, at least give it a harsh pruning in March or April, cutting it back by about two thirds. This will help rejuvenate it and stimulate better bloom.
Give the Jerusalem cherry moderate to intense light, normal indoor temperatures and routine houseplant maintenance (water when the soil is dry to the touch, fertilizer from March to September, increased air humidity in winter, etc.). Watch out for whiteflies (the most common problem), aphids and spider mites and treat with insecticidal soap as needed. The flowers are self-pollinating and thus produce fruits even in the absence of any pollinator. However, more fruits are produced when the plant is placed outside during the summer, suggesting that the action of pollinating insects is still useful.
Note that the berries, even if they are highly appreciated by many birds and mammals in the wild, are slightly toxic to humans, dogs, cats and parrots, especially when they are green. Severe poisonings are rare, however, because it is necessary to consume many unripe berries before symptoms occur. Even so, it is always wise to place this plant out of the reach of children and pets.