Annona muricata is a species of the genus Annona of the custard apple tree family, Annonaceae, which has edible fruit. The fruit is usually called soursop due to its slightly acidic taste when ripe. Annona muricata is native to the Caribbean, India and Central America but is now widely cultivated – and in some areas, becoming invasive – in tropical and subtropical climates throughout the world.
Annona muricata is known as sirsak in Indonesia. Annona muricata is also the main host plant for tailed jay (Graphium agamemnon) caterpillars. They eat the leaves voraciously and usually stick under the leaves to pupate.
Annona muricata is a small, upright, evergreen tree that can grow to about 30 feet (9.1 m) tall. Its young branches are hairy. Leaves are oblong to oval, 8 centimetres (3.1 in) to 16 centimetres (6.3 in) long and 3 centimetres (1.2 in) to 7 centimetres (2.8 in) wide. They are a glossy dark green with no hairs above, and paler and minutely hairy to no hairs below. The leaf stalks are 4 millimetres (0.16 in) to 13 millimetres (0.51 in) long and without hairs.
Flower stalks (peduncles) are 2 millimetres (0.079 in) to 5 millimetres (0.20 in) long and woody. They appear opposite from the leaves or as an extra from near the leaf stalk, each with one or two flowers, occasionally a third. Stalks for the individual flowers (pedicels) are stout and woody, minutely hairy to hairless and 15 millimetres (0.59 in) to 20 millimetres (0.79 in) with small bractlets nearer to the base which are densely hairy.
The petals are thick and yellowish. Outer petals meet at the edges without overlapping and are broadly ovate, 2.8 centimetres (1.1 in) to 3.3 centimetres (1.3 in) by 2.1 centimetres (0.83 in) to 2.5 centimetres (0.98 in), tapering to a point with a heart shaped base. They are evenly thick, and are covered with long, slender, soft hairs externally and matted finely with soft hairs within. Inner petals are oval shaped and overlap. They measure roughly 2.5 centimetres (0.98 in) to 2.8 centimetres (1.1 in) by 2 centimetres (0.79 in), and are sharply angled and tapering at the base. Margins are comparatively thin, with fine matted soft hairs on both sides. The receptacle is conical and hairy. The stamens are 4.5 millimetres (0.18 in) long and narrowly wedge-shaped. The connective-tip terminate abruptly and anther hollows are unequal. Sepals are quite thick and do not overlap. Carpels are linear and basally growing from one base. The ovaries are covered with dense reddish brown hairs, 1-ovuled, style short and stigma truncate. Its pollen is shed as permanent tetrads.
The fruits are dark green and prickly. They are ovoid and can be up to 30 centimetres (12 in) long, with a moderately firm texture. Their flesh is juicy, acidic, whitish and aromatic.