Soursop

Other common names: Guanabana, Prickly Custard Apple, Durian Belanda, Graviola, Durian Europa, Durian Makkah, Durian Benggala, 红毛榴莲

Soursop trees are an uncommon crop that can occasionally be found in edible gardens in Singapore. The fruits are typically eaten raw and are a popular addition to juices and desserts.

As a perennial tree, it is found in edible gardens, permaculture gardens, and low maintenance beds.

Sun and soil needs:

This tree does best in full sun gardens with a minimum of 6 hours of direct sunlight.

Plants do best in pots with loamy soil at least 1m deep, or in true ground. These plants are vulnerable to root rot, so ensure that your pots drain well, and that your soil has plenty of organic matter to let the roots breathe. Keep your plants cool with mulch and plenty of water to encourage growth.

Sowing seeds

Seeds can be sown directly into pots or the ground. Because the plant eventually grows into a tree, it is easier to grow a few seedlings in separate pots before selecting the healthiest one to be grown in true ground.

The seedlings are generally resilient to most environmental factors but may be vulnerable to being eaten by snails or birds. Protect your young plants with a DIY cloche or netting.

Growing:

Soursop trees are steady growers but do benefit from being fed high potassium and phosphorus fertilisers once every two months after its first flower to encourage flowering and thus fruiting. Regular pruning to promote airflow will keep the plant healthy and neat.

This tree can grow up to 10m high. The tree is best maintained at roughly 2m high for easy maintenance and harvesting.

The tree will need to be around 3 years old before it starts producing fruit if grown from seed.

It is currently unclear what pollinates soursop trees in Singapore, but in their native range they are pollinated by beetles. Flowers can be hand-pollinated if male flowers are harvested from another tree.

Harvesting:

Fruits are considered ripe when the spines are far apart, and the skin of the fruit darkens to a dull green or yellowish green. Fruits should be harvested ripe for immediate consumption.

Propagation:

This tree is grown via seed, or via woody cuttings with rooting hormone. This tree can also be grafted.

Common problems & solutions:

If your plant has few to no flowers, you can try fertilising the plant with fertilisers high in phosphorus and potassium. These nutrients encourage root and flower growth, which are important for the plant to produce more fruit.

Many plants require pollinators to help them fruit. Bees, butterflies, birds and even beetles transport pollen from one flower to another, pollinating your crops and increasing their fruit yield. Attract some pollinators to your garden by growing pollinator-attracting crops, or become a pollinator yourself by hand-pollinating your plants.

Aphids, mealy bugs, and spider mites often infest the plant if it is sickly or overgrown. Prune off the infested parts, or apply horticultural oils like neem oil and white summer oil to suffocate the remaining pests. Regularly prune the plant to allow light and air to reach throughout the plant, and check the plant for underlying problems like root rot, lack of sunlight, and nutrient deficiencies.

Whiteflies can infest the plant and lay eggs under its leaves. Remove affected plant parts and catch remaining adults with yellow sticky paper or treat them with citrus spray.

Fruit flies can lay eggs in the fruit, resulting in larvae damaging the fruit and creating spots on the skin. Wrap your fruit in netting when it starts to develop from a fertilised flower, ideally after all the petals have dropped off.

Rodents and birds may eat unripe or ripe fruit. Wrap your fruit in netting when it starts to develop from a fertilised flower, ideally after all the petals have dropped off.