Watermelon

Watermelon (Citrullus lanatus)

Other common names: Tembikai, Semangka, 西瓜

Watermelons are popular fruits typically eaten raw, but they are also added to juices and desserts. There are many cultivars with flesh ranging from classic red to yellow and can grow to a variety of sizes.

An annual crop, these plants are often grown in rotation with other fruiting climbers.

This plant is part of the Cucurbita or melon family, which includes other popular edible fruits like bitter gourd, winter melon, and pumpkin.

Sun and soil needs:

This vine does best in full sun gardens with a minimum of 6 hours of sunlight. It can also be grown in areas with at least 6 hours of indirect sunlight but will produce less and smaller fruit.

Plants do best in pots with loamy soil at least 30cm deep, or in true ground. The plant can be grown in smaller pots about 20cm deep, but growth will be slower and the plant will produce less fruit.

Sowing seeds:

Seeds can be sown directly into pots or the ground around 15-30cm apart. Lightly water the soil until damp, once a day. Seeds should sprout within 10 days.

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:

This plant will produce more flowers and thus more fruit when fed with fertilisers high in phosphorus and potassium. Plants can be fertilised regularly once a month after germination for a fuller crop.

Because the vines will grow on top of each other, it is a good practice to prune regularly and remove dead leaves and vines to improve ventilation and allow light to reach more of the plant.

Young fruits might rot if they are left in contact with wet soil. They can be protected by being placed on well-draining waterproof materials like burlap sacks or small platforms.

As a fast-growing vine, this plant needs space to scramble on the ground or a sturdy trellis to scramble on.

Fruits are heavy and are vulnerable to rot if left in direct contact with the ground. Fruits can be protected from rotting be being placed on well-draining waterproof materials like burlap sacks or on small, elevated platforms. Fruits growing on trellises should be supported with a cradle to prevent the vine from snapping.

As with all members of the melon family, this plant is bee pollinated and produces male and female flowers. To encourage the formation of more fruits, it is best to have at least 3 separate plants growing in the same area to have both male and female flowers available, and to have bee-attracting plants within the garden to encourage pollination.

Harvesting:

Plants can be harvested for fruits around 4 months after sowing. The best time to harvest the fruit is in the early morning, before 9am.

Watermelons are ripe when then the underside turns yellowish. The skin will become dull, and sound “hollower” when thumped.

Harvest cycle:

Propagation:

This vine can be grown via seeds. Seeds can be taken from mature fruit for immediate planting.

Common problems & solutions:

Young plants have soft stems and can be completely eaten by slugs and snails. Grow seedlings till they are at least 10cm tall before planting them in true ground, or use DIY cloches or netting to protect young plants.

If your plant has few to no flowers, you can fertilise 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.

However, if your plant is producing lots of flowers but is not bearing fruit, you may not have female and male flowers present in the same area together. Pollen from the male flower needs to be transferred to the female flower before the female flower can become a fruit. This process is called pollination and is important or the formation of many edible fruits. Vines from the melon family generally produce male flowers before female flowers. Having at least three plants of varying ages in the garden will make both male and female flowers present for pollination to happen.

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.

Aphids, mealy bugs, whiteflies, and spider mites often infest the plant if it has underlying problems like repeated wilting from heat stress. Mechanical pest control methods like pruning the infested parts are the best methods for managing these pests in the short term, but resolving the underlying problem will prevent them in the long term.

Wilting leaves during hot weather is a sign of heat stress. Increase the number of times the plant is watered daily, and apply mulch at the base to prevent water loss.

Fruit flies, can lay eggs in the fruit, resulting in larvae damaging the fruit and creating spots on the skin. Squirrels 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.