Cherimoya (Annona cherimola). Flower and fruit.

Cherimoya - Annona cherimola

The cherimoya, (Annona cherimola)  is an edible fruit-bearing species of the genus Annona from the family Annonaceae. which generally is thought to be native to the Andes, although an alternative hypothesis proposes Central America as the origin of cherimoya because many of its wild relatives occur in this area. Today cherimoya is grown throughout South Asia, South Europe, North Africa, Australia, Central America, and South America, and in Southern California.

Annona cherimola is a fairly dense, fast-growing, evergreen tree, erect but low branched and somewhat shrubby or spreading; ranging from 5 to 9 m in height; and its young branchlets are rusty-hairy. The attractive leaves are single and alternate, 2-ranked, with minutely hairy petioles 6 to 12.5 mm long; ovate to elliptic or ovate-lanceolate, short blunt-pointed at the apex; dark green and slightly hairy on the upper surface, velvety on the underside; 7.5-15 cm long, 3.8-8.9 cm wide.  The leaves are briefly deciduous (just before spring flowering). The fragrant flowers are borne solitary or in groups of 2 or 3, on short, hairy stalks along the branches, have 3 outer, greenish, fleshy, oblong, downy petals to 3 cm long and 3 smaller, pinkish inner petals. 

The compound fruit is conical or somewhat heart-shaped, 10-20 cm long and up to 10 cm in width, weighing on the average 150-500 g but extra large specimens may weigh 2.7 kg or more. The skin may be smooth or slightly tuberculated  or covered with conical or rounded protuberances. The fruit opens to expose the snow-white, juicy flesh, of pleasing aroma and delicious, subacid flavor; and containing numerous hard, brown or black, beanlike, glossy seeds, 1-2 cm long. Mark Twain called the cherimoya "the most delicious fruit known to men". The fruit is fleshy and soft, sweet, white in color, with a sherbet-like texture, which gives it its secondary name, custard apple. Some characterize the flavor as a blend of banana, pineapple, papaya, peach, and strawberry. Others describe it as tasting like commercial bubblegum. Similar in size to a grapefruit, it has large, glossy, dark seeds that are easily removed. When ripe, the skin is green and gives slightly to pressure, similar to the avocado. Many people often chill the cherimoya and eat it with a spoon, which has earned it another nickname; the ice cream fruit.

The name originates from the Quechua word chirimuya, which means "cold seeds," because the plant grows at high altitudes and the seeds will germinate at higher altitudes. In Peru, Ecuador and Colombia the fruit is commonly known as chirimoya, a mixture of the modern and Quechua names.

The cherimoya is believed indigenous to the interandean valleys of Ecuador, Colombia and Bolivia. In Bolivia, it flourishes best around Mizque and Ayopaya, in the Department of Cochabamba, and around Luribay, Sapahaqui and Rio Abajo in the Department of La Paz. Its cultivation must have spread in ancient times to Chile and Brazil for it has become naturalized in highlands throughout these countries. Many authors include Peru as a center of origin but others assert that the fruit was unknown in Peru until after seeds were sent by P. Bernabe Cobo from Guatemala in 1629 and that thirteen years after this introduction the cherimoya was observed in cultivation and sold in the markets of Lima. The often-cited representations of the cherimoya on ancient Peruvian pottery are actually images of the soursop, A. muricata L. Cobo sent seeds to Mexico also in 1629. There it thrives between 4,000 and 5,000 ft (1312-1640 m) elevations.

The cherimoya is subtropical or mild-temperate and does not succeed in the lowland tropics. It requires long days. In Colombia and Ecuador, it grows naturally at elevations between 1 400-2 000 m where the temperature ranges between 17-20 deg. C. In Peru, the ideal climate for the cherimoya lies between 18-25 deg. C in the summer and 18-5 deg. C in winter. In Guatemala, naturalized trees are common between 1 200-2 500 m though the tree produces best between 1 200-1 800 m and can be grown at elevations as low as 900 m. The tree cannot survive the cold in the Valle de Mexico at 2 195 m. In Argentina, young trees are wrapped with dry grass or burlap during the winter. The cherimoya can tolerate light frosts. Young trees can withstand a temperature of –3 deg. C, but a few degrees lower severely injures or kills mature trees. The tree prefers a rather dry environment as in southern Guatemala where the rainfall is 127 cm and there is a long dry season. The tree should be protected from strong winds that interfere with pollination and fruit set.

The tree thrives throughout the tropics at altitudes of 1,300 to 2,600 m (4,300 to 8,500 ft). Though sensitive to frost, it must have periods of cool temperatures or the tree will gradually go dormant. The indigenous inhabitants of the Andes say although the cherimoya cannot stand snow, it does like to see it in the distance. It is cultivated in many places throughout the Americas, including California, where it was introduced in 1871, and Hawaii. In the Mediterranean region, it is cultivated mainly in southern Spain, where it was introduced before 1751 in the Motril, Almunecar and Malaga areas, from where it was carried to Italy and lsla de Madeira (Portugal), but now can be also found in Morocco, Tunisia (only in the orchards of Hammamet), Lebanon, Egypt, Cyprus, and Israel. The first planting in Italy was in 1797, and it became a favored crop in the Province of Reggio Calabria. It is also grown in Taiwan, Australia and New Zealand.

The flowers are hermaphroditic and have a mechanism to avoid self pollination. The short-lived flowers open as female, then progress to a later, male stage in a matter of hours. This requires a separate pollinator that not only can collect the pollen from flowers in the male stage, but also deposit it in flowers in the female stage. Studies of insects in the cherimoya's native region as its natural pollinator have been inconclusive; some form of beetle is suspected. Quite often, the female flower is receptive in the early part of the first day, but pollen is not produced in the male stage until the late afternoon of the second day. Honey bees are not good pollinators, for example, because their bodies are too large to fit between the fleshy petals of the female flower. Female flowers have the petals only partially separated, and the petals separate widely when they become male flowers. So, the bees pick up pollen from the male flowers, but are unable to transfer this pollen to the female flowers. The small beetles which are suspected to pollinate cherimoya in its land of origin are much smaller than bees.

For fruit production outside the cherimoya's native region, cultivators must either rely upon the wind to spread pollen in dense orchards or else use hand pollination. Pollinating by hand requires a paint brush. Briefly, to increase the fruit production, growers collect the pollen from the male plants with the brush, and then transfer it to the female flowers immediately or store it in the refrigerator overnight. Cherimoya pollen has a short life, but it can be extended with refrigeration.

Source:
http://en.wikipedia.org/wiki/Cherimoya
http://www.hort.purdue.edu/newcrop/morton/cherimoya.html
http://www.worldagroforestrycentre.org/sea/products/
afdbases/af/asp/SpeciesInfo.asp?SpID=1728