Root Awakening: Plant's curling leaves could be due to pests or stress
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Check the underside of curled leaves for sap-sucking pests, but note that some may be microscopic.
PHOTO: SOH GUAT HIONG
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Curling leaves could be due to pests or stress
I have three Guiana Chestnut plants and they have developed curled leaves. What is wrong? Can the condition spread to other plants? I have pruned the infected shoots, but they keep recurring.
Soh Guat Hiong
The first possibility is an infestation of sap-sucking pests. Check the underside of the curled leaves for pests, but note that some microscopic ones such as broad mites are not visible to the naked eye. Pests can also spread to nearby plants.
Pest damage can be seen in leaves that have become stiff and brittle with a shiny underside. If it is a pest infestation, regular applications with lime sulphur or abamectin may help control the situation. If you find other sap-sucking pests such as aphids, spray the plants thoroughly with diluted castile soap or summer oil. In both cases, you can prune deformed and infested leaves.
Another possibility is that the plants need a change in location - for example, the area near the exhaust vents of air-cooling systems is not ideal for plant growth. Environmental stress can damage young leaves, which are soft and tender, and lose moisture easily. Environmental stress-induced damage will not spread to other plants.
Happiness tree's fruit is edible
What plant is this? Is the fruit edible?
Chong Chiow Mooi
The tree is commonly known as the Happiness Tree (Garcinia subelliptica) and it is a relative of the common mangosteen. It is a slow-growing tree that is often planted in Singapore's urban gardens. The fruit, which turns orange and fragrant when ripe, is edible and has a sweet-sour flavour.
Orchid is a type of antelope dendrobium
What type of orchid is this?
Wong Mun Wai
From the two upright petals, your orchid appears to be an antelope Dendrobium hybrid. These plants usually require at least six hours a day of direct sunlight to thrive, and regular feeding with fertiliser to promote flowering. Orchids are epiphytes and usually need chunky charcoal growing media to flourish in Singapore's tropical climate.
Walidda plant may need to be repotted
My plant was growing well, almost doubling in height to 70cm and producing dark green leaves. However, in the past few months, the leaves have been turning yellow and falling off, and the plant has also stopped flowering. I added more soil to the pot and fertilised the plant, but to no avail. The undersides of the leaves also began to feel sandy and rough. What is wrong?
Kay Wong
The plant is botanically known as Wrightia antidysenterica and its common names include Walidda, Arctic Snow, Milky Way and Snowflakes.
This plant thrives in a spot which gets direct sunlight for at least six hours a day. If you had recently moved the plant to a darker location, the sudden change in light intensity might have caused the leaves to turn yellow and fall off.
Check if your plant's roots have filled the pot. In such a situation, the roots have little space to grow and nutrients in the growing medium may have been exhausted. The plant will also dry out quickly, even with regular watering. These factors can also lead to the yellowing and dropping of leaves. Topping off the soil will not be enough to remedy this.
Try moving the plant into a larger pot. During the process, gently untangle the circling roots and be careful not to break them. Put the plant in a slightly shady spot for it to recover for about a week before moving it back to a sunny location. Regular feeding and direct sunlight are both essential for the plant to flower.
Young okra plants need room to grow
What plant is this and is it edible?
Yeo Suat Lay
The plants are lady's finger (Abelmoschus esculentus), commonly known as okra.
Your pot is too crowded and the plants look lanky, which indicates a lack of sunlight. Lady's fingers are large shrubs, so it is best if you grow each plant in a pot measuring at least 50cm in diameter and depth.
At this stage, it is difficult to separate the young plants without damaging the roots. You can prune most of the plants, leaving the healthiest shoot. Move the remaining plant into a bigger pot for optimal growth.
Lady's fingers require at least six hours a day of direct sunlight to thrive and they grow best outdoors in sunny gardens.
- 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.
- Have a gardening query? E-mail it with clear, high-resolution pictures of at least 1MB, if any, and your full name to stlife@sph.com.sg. We reserve the right to edit and reject questions.
