Root Awakening: Plant needs more light and a bigger pot

Clerodendrum chinense (Osbeck) with beige spots on it.

PHOTO: TEA ANN LEE

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Plant needs more light and a larger pot

I have a potted plant which I believe is Clerodendrum chinense (Osbeck). It once produced fragrant white blooms, but it attracted ants.

I gave it eggshells for calcium, which probably led to the yellowing of the leaves. I removed as much of the eggshells as I could, but the leaves continued to yellow and eventually withered.

I suspect the plant has been infested with pests, as there are beige spots on other parts of it. I scraped the spots off, but now it seems that very few leaves grow from the stem. These pests also appeared on my South Africa Bitter Leaf and Hoya Australis plants. How should I deal with them?

Tea Ann Lee

It appears that the area where your plant is being grown is a little too shady to support healthy growth. The pot may also be too small for the plant.

The leaves with brown spots appear to indicate infection with a fungal disease. Eggshells, depending on how much you have added and how finely they have been crushed, take very long to release calcium and should not pose an issue in most instances.

Move the plant to a larger pot with fresh potting mix and feed it with a water-soluble fertiliser that has the nutrients it needs to grow. Increase its exposure to light, but do so gradually to avoid burning the leaves. Clerodendrum chinense requires at least six hours of direct sunlight a day.

You can prune the severely infected leaves. Small sucking pests on the leaves can be managed by washing them away and spraying the leaves regularly with a diluted soap solution or summer oil.

Remove diseased chilli plant

This chilli padi plant was growing well in my garden until after the first harvest. The leaves then started to curl and turn yellow. Is this a disease? How can I treat this?

Chan How Kiat

Your plant appears to have been infected with a viral disease for which there is no cure. It is best to remove infected plants immediately to prevent the disease from spreading to other plants in the area. Viral diseases can be spread by cutting tools, as well as sucking insects such as aphids and white flies that are commonly found on chilli plants.

If you had used your cutting tools to prune your chilli plant, they must be sterilised. You can manage sucking insects by applying pesticides such as summer oil and pyrethrins to prevent the spread of disease.

Evaluate past growing practices

I have a Thai jambu plant that bore abundant fruit until about two years ago. It has since stopped. What should I do?

Phuah Swee Hoe

You may want to compare your current growing practices with those of the past in order to determine why your jambu tree is no longer fruiting.

Note that the tree produces flowers in its new growth phase. As such, pruning can keep the tree size manageable, and prevent the production of flowers and fruit. After pruning, the tree has to channel resources towards producing new growth before going back into reproduction.

For a healthy tree, keep the root zone free of weeds up to the dripline - the area directly located under the outer circumference of the tree branches - and turf and mulch the base with high-quality compost or dried leaves.

If space is an issue, grow grafted fruit trees in large flower pots. These will bear fruit at a smaller size and are easier to manage.

Bumps on tomato plant's stem are roots

Some hard white bumps are forming at the base of my cherry tomato plant. What are they?

Ang Sindy

The bumps along the stem of your tomato plant are adventitious roots, also known as aerial roots. They will produce normal roots if placed in contact with moist soil.

These roots are usually no cause for concern, but check their health below the soil level - you can do so by carefully taking the entire root ball out for inspection. Healthy roots should be white and firm.

The production of adventitious roots is sometimes associated with wet, compacted and poorly drained soils that may affect the plant's overall root health.

Dracaena Fragrans infested with sap-sucking pests

This plant has a waxy substance on the surfaces of almost all the new leaves. What is it and is it harmful?

Choy Ngai Mun

Your Dracaena fragrans has likely been infested with mealy bugs, sap-sucking pests which are covered in a sticky, cotton-like wax.

You can use a jet of water to wash them off and reduce the number of pests you need to deal with.

Summer oil or castile soap solution can be used to kill the remaining mealy bugs. Spray your plant thoroughly, especially the tight spaces between the leaves, which may serve as hiding spaces for these pests. Consistent, repeated pesticide applications are often needed to ensure all subsequent generations of the pests are eradicated.

Grow your plant under optimal conditions to reduce the likelihood of pest issues. The Dracaena fragrans fares best when it gets four to six hours of filtered sunlight a day. It is not an indoor plant and will grow poorly in deep shade.

Check your plant regularly for pests to nip any issues in the bud.

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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