Annona squamosa

Sugar apple, sweetsop, custard apple


Native to the neotropics and in these areas is the most widely grown species in the genus. Now grown in many other tropical and sub-tropical regions worldwide, including Australia.


In Colombia it grows mainly in lowlands and less frequently up to 1300m. It is the most drought tolerant of the fruiting Annonas and grows well with more than 700mm pa, but poorly if excessive. They will survive extended dry conditions when mature but at the cost of yield. Trees have little tolerance to frost, especially when young, and ideal prevailing temperatures and relative humidity are 15-30°C and 70% resp, especially during flowering and fruit set through to maturity.

Plant Description

A small low spreading tree with a shallow root system, thin grey-brown bark and a dense canopy, 3-6m high. Simple entire alternate semi-deciduous leaves on short peitioles (0.4-1cm long) are oblong-lanceolate to narrowly elliptic, 7-17 X 3-5cm, glabrous above, slightly pubescent below, and have brochidodromous venation. Growth is by vegetative flushes, and lateral buds may consist of up to 2 vegetative and 3 flower buds.


Sugar apple is a species in the Annonaceae family that contains 130 genera and around 2500 species. The genus Annona has about 120 species including several that produce valued fruit, namely cherimoya, atemoya (a hybrid of cherimoya and sugar apple), pond apple, soursop, mountain soursop, bullock’s heart and rollinia. It is a diploid species with 2n = 14.


It tolerates sandy soils to clay loams but is sensitive to salinity, whether coastal wind-borne or in the soil. Well drained soils with pH 6-6.5 are preferred.


Usually by seeds that are orthodox; storage at ambient temperature for 2-4 months appears to break any apparent seed dormancy/immaturity and gives best germination results. Soak for 3-4 days to allow sufficient imbibition & they should then germinate in 20-30 days if maintained at 25-30°C. There seems to be little sexual variation between parents & their seedlings (although plants from different regions show considerable heterozygosity), but they are preferably used as rootstocks for scions from good performing trees. Buds are sub-petiolar, so for best results branches chosen for scion material should be defoliated while still on the tree to induce bud-swelling over the following 1-2 weeks, and then grafted afterwards. Sugar apple can also be grafted on cherimoya with good results as the 2 species are close taxonomically. Rootstocks can have a big effect on yield. Low success rates have been reported with cuttings and marcotting; inarching is possible but not preferred.


No proper breeding work has been conducted but some varieties have been selected elsewhere in the world such as Mammoth, Arka, Washington, Barbados, Thai Lessard, several red/purple skinned varieties, and some that have far fewer seeds than normal eg Cuban, Brazilian and Thai Seedless – never as big or flavoursome as normally seeded fruit. They are all difficult to source in WA and none has all the desirable properties sought by breeders.

Flowering and Pollination

Supra-axillary leaf-opposed inflorescences have pendent slightly fragrant hermaphrodite flowers (2-3cm long), single or 2-3 fasciculate. Outcrossing is promoted by protogynous dichogamy. Small triangular sepals (3-4) are deciduous, and petals (6-8, 1.5-3 X 0.5-0.8cm) are arranged in two whorls, the outer fleshy yellow-green forming a narrow floral chamber at anthesis, and the inner inconspicuous. Numerous carpels surround the central conical receptacle with many tightly-packed stamens (<1mm long) at the lower periphery. Pistils with partially connate styles and distinct stigmas contain a single ovule. There is an interesting twist to pollination and fertilisation. Pollen grains (many thousands) are released singly or in groups of up to 4 which separate when deposited on stigmas; these are of the wet type, and copious secretions triggered by anthesis totally engulf the pollen. This pool of pollen grains can then pollinate adjacent stigmas resulting in multiple ovules being fertilised, providing an understanding of the many-seeded fruit characteristic. There is effectively no chill hour requirement. With normal anthesis (temperature and humidity 22-30°C and >80% resp) the stigmas are receptive mid-morning and pollen is released 24 hrs later, but with lower temperatures and high humidity, stigma receptivity may be extended sufficiently for considerable self-pollination to occur. Natural fruit set is low (1-4%) but this can be markedly improved with hand and/or cross-pollination; fertile pollen can be collected from fully open flowers when the pollen sacs have turned from white to cream. High temperatures (>30°C), low humidity (<30%), and rain will compromise pollination and fruit set. Flowering can continue over an extended period (3-6 months), and various types of small beetles are the natural but not very efficient pollinators, with wind playing a much smaller role.

Pollination of only some carpels results in small and malformed fruit.


A full sunlight position is preferred. Fertilisation practice should be little and often. Watering should be reduced in the period before flowering, and then ample should be provided during flowering, fruit set and growth through to maturity.

The total amount of NPK should increase commensurately with tree size, but too much will favour vegetative growth over reproductive. Humidity within the canopy during flowering can be improved by under-tree sprinklers or over-head misters. Micronutrients may need attention – B and Ca deficiencies are common and can be addressed by foliar sprays.

Wind Tolerance

The soft wood makes the tree vulnerable to strong winds, which also can cause fruit blemishes due to rubbing. Wind can also reduce humidity within the canopy, negatively affecting pollination.


If the tree is not opened out, light penetration to lower levels of the dense canopy will be low, resulting in low fruit set. Tree shaping should start when the plant is young and appropriately spaced main scaffold branches can be selected; subsequent growth and pruning should endeavour to keep the canopy open. Trees should be maintained at no more than 3m high for ease of management and harvesting. Annual pruning is best when trees have been dormant and are just coming into spring, but summer pruning can delay harvest by a few months if this is desired. If fruit set is high, then thinning should aim for 1-2 fruit per lateral.

The Fruit

The fruit is a globose-ovoid syncarp, 100-500g and 5-10cm long and wide, formed by many loosely connected carpels and a fleshy receptacle. The thin knobbly skin is separated by deep grooves that become yellow-green with maturity, and the white slightly cream pleasantly sweet aromatic flesh contains 30-40 poisonous shiny black bean-shaped seeds, 10-14mm long. Adjacent carpels are not completely fused and sometimes those closest to the peduncle can separate on ripening, exposing the underlying white flesh. Seeds and skin represent up to 40% of fruit weight. It has reasonable levels of Vitamin C, acidity is mainly due to citric and malic acids, and carbohydrate content of fully ripened fruit is 20-28%, the highest of all the fruiting Annonas.

Fruit Production and Harvesting

The juvenility period for seedlings is 2-3 years, and full production may take 5-6 years. As usual while plants are young, remove any fruit that may form within the first 1-2 years with the goal of rapidly establishing mature tree size. Fruit growth exhibit a double sigmoid pattern taking 15-18 weeks from anthesis to maturity in the tropics, and are usually picked in late summer autumn for best flavour while mature but still firm. With approach to harvest times, fruit splitting is more prevalent with variations in moisture content, and low temperature and humidity can cause fruit russeting. Good management and pollination with mature trees may produce 50 or more fruit/tree/year. Fruit should be cut from the tree with about 1cm of the peduncle to minimise disease development during ripening, and care needs to be exercised as the thin skin is easily bruised. Sugar apple is a climacteric fruit and final ripening at ambient temperature (ideal 20-25°C) usually takes 3-6 days. Fruit are highly perishable and if stored fresh for too long, declining acid and sugar levels result in a bland taste. Storage below 15°C will cause chilling injury.

Fruit Uses

Usually eaten fresh, or as nectars, milkshakes and smoothies after seed removal. Flesh can also be frozen to extend storage for a few months, longer if some lemon juice is added.

Pests and Diseases

Problems are usually minimal in our dry climate, but diseases reported elsewhere include bacterial wilt, anthracnose, black canker causing mummified fruit and Armillaria root rot. Possible pests include Medfly (rare) and mealy bugs.

Competing weeds should be removed.


Sugar apple is well suited to our climate and seedlings have a relatively short juvenility period. As a small tree, those without acreage can contemplate growing one. It is more self-fertile than the most commonly grown Annona in Australia (atemoya), but still benefits from high humidity at flowering time to minimise stigma desiccation. Commercial opportunities for the species are limited because of high perishability and low transportability, but these factors are not a problem for the home grower. It could be grown in a pot for some years.