Root Awakening

Yucca plant
Curry tree

Rose-Flowered Jatropha may be lacking water

The leaves of my Jatropha plants turn limp and yellow before they shrivel and drop off . Why is this so?

Sheena Goh

Your Jatropha integerrima (common name is Rose-Flowered Jatropha) looks like it is dehydrated, with its yellow, shrivelled leaves.

Ensure the plant is watered regularly so that it is hydrated at all times. This is especially so if it has just been planted.

Make sure the soil is not overly compacted, as water may not be able to permeate to the roots below.

Was there construction work done near the plant recently? If there was, it might lead to root disturbance.

Root injury can also affect the uptake of water by the plant. If the injury is not too intensive, the plant will recover if given time.

If you have been watering regularly, you may want to check the health of the plant's roots.

Jatropha plant

Soil-dwelling pests such as soil mealy bugs and beetle grubs may be feeding on the roots which prevent the plant from absorbing water. Use chemical pesticide drenches to eradicate such pests.

Last but not least, ensure your soil is not waterlogged as such a condition will lead to the roots dying.

The Rose-Flowered Jatropha requires a well-drained site to thrive.

Curry tree is dehydrated

I have been growing this plant for more than a year in my balcony. Its growth is stunted and the plant has turned yellow. How can I salvage it?

Seah Guek Eng

Your curry tree (Bergera koenigii) looks dehydrated with its yellow, shrivelled leaves. Check if your plant is pot-bound, a situation where the roots have filled the pot. You may want to move it to a larger pot.

The soil may also be compacted and lacking in organic matter. Use a fork and add some good quality, mature compost into the soil of the plant. Take care not to damage the roots of the plant. Also, ensure that you water your plant regularly to keep it hydrated at all times.

There seems to be yellow spots on the leaves. They may indicate an infestation of spider mites. These sucking pests appear as small red dots on the underside of leaves. They affect stressed plants that are grown in dry environments.

You may want to prune the affected leaves. If the growing conditions improve and are optimal, new leaves will be healthy. You should grow your curry tree in a well-lit location and increase the humidity around the plant.

Also, the soil mix should be aerated, of good quality and containorganic matter.

Scale insects infesting yucca plant

I bought this yucca plant years ago and kept it in my balcony. As it grew taller, the leaves turned brown and withered. What is wrong with it and how can I save it?

Ang Beng Yew

The yucca plant (likely Yucca aloifolia) is suffering from a bad scale insect infestation.

You may want to remove the badly infested leaves.

The remaining foliage will need to be sprayed thoroughly with summer oil or neem oil. The oil will suffocate the insects. Repeated applications will be needed to keep the pest population under control.

The yucca plant is a light-demanding plant that requires at least six hours of direct sunlight a day to grow well. The lack of light will lead to an unhealthy plant that is prone to pests and diseases.

To help your plant grow better, consider improving the growing conditions.

• Answers by Dr Wilson Wong, a certified practising horticulturist and founder of Green Culture Singapore (www. greenculturesg. com). He is also an NParks-certified park manager.

• Have a gardening query? E-mail it with clear, high-resolution pictures of at least 1MB, if any, and your full name to stlife@

A version of this article appeared in the print edition of The Straits Times on January 20, 2018, with the headline 'Root Awakening'. Print Edition | Subscribe