Branch of StarApple with fruits
Photo by George Allen, Queensland

Star Apple

Chrysophyllum cainito

Origin:

West Indies. Now grown in many of the warm parts of the world.

Climate:

Best adapted to hot and humid tropical climates up to 800m with a definite dry season. Temperatures of 4°C and below will cause defoliation and then more severe damage and death.

Plant Description:

An ornamental, large, tropical evergreen tree, 8-25m tall.  The alternate oblong-elliptic leaves, 5-15 x 3-5cm, are glossy green on the upper side and golden brown underneath.

Relatives:

A member of the Sapotaceae Family which also includes the mamey sapote, sapodilla, canistel and abiu.

Soils:

The tree is not particular as to soil, but it needs perfect drainage and prefers slightly acid soils.

Propagation:

Mostly by seeds, which produce variable results. Cuttings of mature wood root well. Air-layers can be produced in 4 to 7 months and bear early. Budded or self-grafted trees have been known to fruit 1 year after being set in-ground.  It can be inarched on star apple seedlings and tip cuttings can be rooted under mist.

Cultivars:

There are a few named cultivars; some available in Australia are Haitian, Grimal and Pink.

Flowering and Pollination:

The inflorescence is axillary, ramiflorous or cauliflorous on current season's growth with 5-30 individual flowers.  These are hermaphrodite with a tubular 5-lobed corolla, 5-6 sepals, 5 stamens, a 7-11-lobed stigma and they’re usually self-fertile (autogamous).  Flowering occurs in late summer to early autumn.  Insects are the main pollinators.

Cultivation:

Young trees should be watered weekly.  Irrigation during and after the flowering period will improve yield.  They can survive without any fertiliser but productivity is improved, particularly in limestone and other infertile soils, if NPK is given from a young age, increasing to 3kg/tree/year as they mature.

Wind Tolerance:

Poor, needs shelter from wind.

Pruning:

Pruning is not extensive, with 3-4 main branches established when young, and dead or crossing branches removed and size containment when mature.

The Fruit:

Fruit are berries, almost spherical, 4-8cm in diameter and surrounded with a leathery skin that comes in two types when mature, green and purple. Flesh is white to purple depending on type, sweet and jelly-like and contains 3-10 small seeds. The common name star fruit derives from the pattern seen when the fruit is cut transversely. Perhaps their best nutritional feature is a reasonable Ca level; carbohydrate content of the flesh is about 15%.

Fruit Uses:

The skin and rind are not edible. Don't bite into the whole fruit or allow the bitter latex of the skin to contact the flesh.  Ripe fruit may be cut in half and the flesh spooned out. Fresh pulp may be mixed with other fruits or fruit juice.  The edible component is 50-60% of the whole fruit.

Fruit Production and Harvesting:

The juvenility period of seedlings is 5-12 years, grafted, 4-5.  Fruit keep better when picked with a slight stem remaining. Star apples are generally in season from late winter or early spring to early summer. They don't fall when ripe but must be hand-picked. Take care to pick only fully ripe fruits, soft to the touch, skin a trifle dull and wrinkled; otherwise, they will be gummy, astringent and inedible.  Examine from above to ensure it has only a very small ring of green (about as big as your thumb nail) around the stem.  Any greener than this and the star apple would contain unacceptable levels of latex and be lacking in flavour.  Ripe fruits will last up to 3 weeks in a refrigerator. A mature tree may bear up to 60 kg of fruits.

Pests and Diseases:

Birds, fruit fly, fungal infections, stem-end decay, leaf spots.

Comments:

This tree could be grown purely for its attractiveness. One of the tropical exotic fruits rarely seen in WA.