Cherimoya

The cherimoya is regarded by many as being among the best of tropical fruits.  The cherimoya has a texture of a soft, non-gritty pear and a delicate, highly appealing fruit flavor with little acidity. Cherimoyas usually are eaten fresh; however they are excellent in ice cream and sherbets.  The seeds, leaves, and limbs contain poisonous alkaloids that have been used to kill lice.  Taken internally, these alkaloids act as an emetic and cathartic and should be regarded as poisonous. The biggest drawbacks in production in California are that the flowers usually require hand pollination to ensure a good set of fruit, and ripen over an extended period; however, from a marketing standpoint these shortcomings can be turned into advantages.  A recent appearance or introduction into the Santa Barbara area, of the trash beetle or Rove beetle (Staphylinidae), may provide sufficient pollination to eliminate the need for hand pollination.  The species is not readily grown outside of its native (high elevation tropics) habitat. In the United States, only the southern California coastal climates are conducive to cherimoya production.  Southeast Asians and Hispanics prize the fruit and a national market has been established in gourmet groceries. The fruit commands a premium price in these limited market places.

Botany

The Annonaceae family consists of 50 genera of which Annona (about 100 species) and Rollinia (about 50 species) are the most important commercially.  The most esteemed of the fruits of this family is the Annona cherimola.  The family is tropical and semi-deciduous in habit. The cherimoya drops its leaves in late spring (or early summer) after which it blooms. Its leaves are alternate, ovate to elliptical (1.5 to 3.5 inches wide by 3 to 6 inches long) with a slightly hairy upper surface.

The family exhibits a protogynous dichogamous flowering habit, that is, complete flowers in which the stigma is receptive before the pollen is ready to shed from the anthers.  This condition is very important in cherimoya since the configuration of its flowers is not conducive to pollination by natural means.  Therefore, pollination is done by hand: pollen is usually collected in the late afternoon or evening, stored in a cool place, and applied to the mature stigmas which are usually receptive in the morning.  Cherimoya flowers, borne solitary or in groups of 2 or 3, are pendulous having three fleshy petals, a green to brown exterior, white interior, and are 1 to 2 inches in length.

As is typical of the family, the cherimoya fruit is formed by the fusion or partial fusion of the carpels resulting in a more or less bumpy fruit with many seeds.  Cherimoyas ripen in 5 to 8 months after pollination changing in color from a darker to a light green or greenish tan, 3 to 8 inch ovoid weighing  1/2 to 6 lbs. In California fruit ripens from November to June.

Other members of the family that are grown for their fruit are:

• Sugar apple or custard apple (Annona squamosa)
• Atemoya (A. squamosa & A. cherimola)
• Soursop (Annona muricata)
• Ilama (Annona diversifolia)
• Bullock's heart (Annona reticulata)
• Biriba (Rollinia deliciosa)
• Pawpaw (Asimina triloba)

Annona squamosa resembles the cherimoya in texture and flavor and, since it is the more widely adaptable to humid conditions, it is the most widely planted in the more tropical parts of the world.

Climatic requirements

All of the species grown for fruit require a tropical or semitropical climate except for the pawpaw which is native to temperate North America.  Moreover, all but the cherimoya are better adapted to wet tropical conditions.  The cherimoya's home is the highland tropics which are often characterized as areas of eternal spring with temperatures seldom straying from the 60's^o (F). There are wet and dry seasons with typical annual rainfalls being about 50 inches.

The cherimoya is adaptable to Mediterranean climates. In addition to San Diego and Santa Barbara and Ventura counties in the United States, significant commercial plantings have been made in Chile, Spain, Peru, Israel, New Zealand, Australia and Italy.

The cherimoya requires a relatively frost-free environment similar to lemons (short periods of 26^oF for mature trees of hardy varieties). Some chilling seems beneficial (50 to 100 hours between 32^oF and 45^oF).  However, a sunny location is needed since sufficient heat is required to develop a good flavor (inland, protection from extremely hot temperatures and dry winds is more important). In California most varieties do well extending 3 to 15 miles inland from the ocean. Further inland, care must be exercised in selecting a variety that will do well. The cherimoya will not tolerate prolonged high humidity, such as is encountered in Florida.

Soil Requirements

The most critical soil requirement is that of good drainage. Sandy loam or decomposed granite is preferred, but  cherimoyas will succeed on many soil types with pH 5 to 8.

Cultural Requirements

Spacing

Trees are normally planted on 20 to 25 foot centers in California.  Tighter centers are used where intensive pruning is employed.

Fertilization

Cherimoyas respond to fertilizer applications generally provided every 3 months with a balanced fertilizer such as 8-8-8.  Yellow leaves may not indicate a need for fertilizer but may be a response to cold temperatures or to the soil being too dry or wet.

Pruning

Train to 2 scaffold branches. Severe pruning (2/3 of new growth) is popular in order to aid in picking. Only shoots that are approximately 60 degrees from trunk are normally saved.

Pests and Diseases

Cherimoyas are generally disease free.  They are susceptible to Armillaria (oak root fungus) and Verticillium wilt.  Good drainage and watering practices will minimize these problems.  Similarly crown rot can occur if care is not taken in keeping the crown of the tree relatively dry.  Ants are a problem since they promote mealy bugs on the fruit.  Ants are most easily controlled by limiting access from the ground by placing a mechanical or acceptable chemical barrier on the trunk of the tree.

Propagation

Although seedlings have a good probability of producing acceptable fruit, trees are normally grafted or budded on seedling rootstock to ensure reliable results.  Grafting is done in the spring at or before leaf drop.  Scion wood should be collected just before leaf drop.  Plants also can be rooted from cuttings, although it is somewhat difficult.  Seed has good viability for 2 to 3 years if stored properly.

Harvesting and Storage

Harvesting is done by hand while the fruit is still firm on the tree (February to April depending on location). The crop is normally hand pollinated to ensure a long harvest season.  Ripeness of fruit must be determined by the color of fruit.  Depending on the variety, the fruit turns from a deep green to a light green or greenish tan.

The fruit is packed in single layer containers to prevent bruising.  If stored, temperatures should not go below 50° F.

Fiscal

The fiscal aspects of orchard investment are similar to that of lemons.

Market

Market has exceeded demand and supported a significantly higher market price which offsets the need for hand pollination and picking.

Compiled by Robert Vieth, Master Gardener