Connoisseurs of tropical fruit consider ripe cherimoyas (Annona cherimola) one of the ultimate indulgences. The trees are hardy in U.S. Department of Agriculture plant hardiness zones 9 and 10, and need the unusual combination of cool, frost-free and dry weather to grow and produce well. The harvest season depends on the variety, as well as the intervention of the grower to hand-pollinate the flowers and initiate fruit formation at the right time.
As a tree from tropical latitudes, cherimoyas exhibit a wide fluctuation in flowering and fruiting times that corresponds more to rainfall patterns than temperature. The climate of Southern California -- which is the only area in the continental United States where the plant grows well -- results in cherimoyas ripening between November and early June. The exact ripening time depends on the cherimoya variety and other variables, but the fruit generally matures five to eight months after pollination.
The harvest period is really a function of when the trees flower or, more precisely, when the flowers are pollinated. Cherimoyas are pollinated by specially adapted insects in their native habitats, but in the U.S. they are reliant on hand-pollination to set fruit. The trees have the unusual habit of losing their leaves in late spring or early summer, with the flowers developing when they recover from dormancy a short time later. Then, it is up to the grower to pollinate each flower. Cherimoyas don't bloom all at once, giving the option to hand-pollinate over an extended period. This practice results in an extended ripening period, corresponding to the time of pollination.
Signs of Ripeness
The main sign of ripeness in cherimoyas is a slight color change from green to yellow-green. The fruit gives slightly under pressure when ripe on the tree, though it should be picked while still firm. It is best to clip the fruit from the tree with a short piece of stem attached, because plucking it by hand can result in bruising. The harvested fruit will finish ripening indoors at room temperature for several days. It will emit a sweet, fruity fragrance when perfectly ripe.
The exact ripening time depends, in part, on the variety. "Ryerson" is an early-ripening variety with smooth or slightly indented skin and excellent flavor. "Deliciosa" is an example of a mid-season variety that does well away from the coast. It has exceptionally large fruit and thin, bumpy skin. "Carter" ripens toward the end of the cherimoya season. This variety has elongated, conical fruit, and the trees have unusual twisted foliage.