The term custard apple tree is applied in two different ways: Some use it to describe all members of the genus Annona, while others only apply the name to the species Annona reticulata. Fortunately, while the genus Annona is quite large (with approximately 150 to 175 species, depending on the authority consulted), the species all share a variety of similar traits.
Most custard apple tree species are native to Central America and Africa, although several species have been domesticated and are grown in suitable climates the world over. The fruit of several species has significant commercial value, particularly in the developing world.
Size and Shape
Custard apples are medium-sized trees that usually reach heights of between 15 and 40 feet. They aren’t considered especially attractive trees, so they are typically grown for food production rather than as ornamentals. Additionally, custard apple trees have very soft wood that breaks easily – particularly when the branches are weighed down with a full fruit crop. Most commercial custard apple farms utilize wind breaks to help protect their trees and maximize their crop.
Nevertheless, custard apple trees can be planted ornamentally, although they only thrive in U.S. Hardiness Zones 7 through 9. Skillful pruning can improve their appearance and help keep them looking their best. Despite the fact that they aren’t ideal shade trees, they do offer most of the same benefits that similarly sized trees do (such as providing shade and wildlife habitat as well as reducing local temperatures).
Their deciduous leaves are about 5 to 8 inches long and rather narrow. They are typically dark green on their top surface and lighter green beneath.
Fruits and Flowers
The flowers of custard apple trees are somewhat bizarre-looking. In fact, they never open completely the way most other flowers do. They bear three extraordinarily long outer petals and three smaller inner petals (the inner petals are very difficult to see). This flower construction belies their close relationship with paw paws (Asimina spp.). Large horned beetles appear to be the primary pollinators of most Annona species.
The resulting fruit is somewhat large and equally strange. Varying in shape from oblong to spherical (and occasionally heart-shaped), the ripe fruit varies between yellow and red in color. The taste is described as being custard-like, which is the reason for their common name.
Custard apples grow best in very well drained soils. Although they do produce a significant taproot extending vertically below the trunk, the bulk of the absorbing roots reside in the upper layers of the soil. However, these trees are very susceptible to root rots and bacterial wilt. In fact, The Queensland Department of Agriculture and Fisheries recommends that growers refrain from planting custard apple trees in soils that formerly harbored tomatoes, potatoes, eggplant and several other common crops, due to the likelihood that bacterial spores may already lurk in the soil. However, root-zone issues aside, custard apples do not often succumb to many pests and diseases that afflict other fruiting trees.
Custard apple trees require warm temperatures to thrive, and they grow best in areas with long, humid summers and mild, dry winters. Established custard apple trees can survive moderate droughts, but without ample rainfall and relative humidity levels of 70 percent or more, custard apple trees may shed their leaves and produce a minimal crop.
Several components within custard apple trees are potentially bioactive, and several primitive cultures use different parts of the plants for medicinal purposes. Some of the plants in this genus produce toxic seeds, which can cause a degenerative neurological condition in humans. Strangely, this only seems to occur on the island of Guadeloupe.
The leaves of custard apple trees also bear several bioactive compounds. They not only possess insecticidal chemicals; their tannins are used to make dyes.