Keep plant alive by controlling population of sap-sucking insects

I grew this basil plant from a stem cutting. It was healthy at first, but its new leaves are smaller and curled. What is wrong?

Yeo Ee Sam Licia

Your basil plant is probably infested with sap-sucking insects such as aphids.

Pick a curled leaf and open it up to check for pests. As the curls protect pests from predators and insecticide, you will need to remove all the curled portions.

The population of sap-sucking pests can generally be controlled by spraying plants with summer oil or castile soap solution. Regular applications are required to keep the pest population low.

The small size of the plant could also be due to a lack of fertiliser, but avoid over-fertilising as it may also give rise to pest issues. Basil plants grow fast and become pot-bound quickly. You may want to move your plant to a larger pot.

The small size of the plant could also be due to a lack of fertiliser, but avoid over-fertilising as it may also give rise to pest issues.

Vine is the Madras pea pumpkin

What is this plant? It looks like bitter gourd, but it has yellow flowers and small, round green fruit that turn red when they are ripe.

Eng Tee

The plant is likely the Madras pea pumpkin and its botanical name is Cucumis maderaspatanus. Sources say the plant and its fruit are likely toxic, so do not eat them.

Check health of lemon tree’s roots

The leaves of my lemon tree have turned yellow and are shedding. The fruit’s skin is brown and leathery. What is wrong with my tree?

Chua Beng Ee

Your lemon tree appears to be drying up due to a lack of water. Has your plant not been watered for some time? In severe cases, the roots could have dried up and died, and the plant cannot be salvaged. 

However, lemon trees do not tolerate wet feet. Ensure the plant is grown in a well-draining mix and not planted too deeply. If you have applied mulch, ensure the collar at the base of the plant is not buried. Constant wet feet can lead to disease.

Plant is the noni

This unknown plant is getting taller. Will it take nutrients away from the other plants in the pot? Should I remove it?

Chua Li Lian

The broad-leafed plant is the noni, which is also called Mengkudu locally. Its botanical name is Morinda citrifolia, and its leaves and fruit have medicinal properties. It can grow into a small tree, so move it to a larger container if you want to keep it.

Plant is a Ficus species

I was planting lady’s fingers and found this plant instead. It grows very fast and became so big that it had to be repotted. What is this plant? Will it bear flowers and at this rate, will it grow into a tree?

Shirley Kwok

The plant is probably a Ficus species, commonly called fig trees. If you cut a leaf off a branch, the wound should produce a milky white sap. Some species grow into large trees, which can have aggressive root systems. Grow the plant in a large pot to contain it. 

Fig plants can be grown for their ornamental leaves, but they do not produce attractive flowers. Instead, they grow flowers in unique fleshy receptacles called syconia.

• Answers by Dr Wilson Wong, an NParks-certified practising horticulturist, parks manager and ISA-certified arborist. He is the founder of Green Culture Singapore and an adjunct assistant professor (Food Science & Technology) at the National University of Singapore.
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