Root Awakening

Gunshot holes caused by bagworms
Gunshot holes caused by bagwormsPHOTOS: DENNIS LEE, GREG CHONG, NATHANIEL FOO, SHEENA GOH, TAN QIU LING

Lemon Cypress difficult to grow in Singapore

This plant looks like a Christmas tree. What is its botanical name? Does it need strong sunlight or should it be placed indoors? Also, what kind of soil does it need and how much fertiliser should I add?

Nathaniel Foo

This plant is commonly known as the Lemon Cypress (Cupressus macrocarpa "Goldcrest"), which has a distinctive chartreuse foliage. It is best treated as a festive display plant in tropical Singapore.

It thrives in cooler temperate climates and hence is difficult to keep alive here.

For display, you can place it in a location with filtered sunlight for at least four hours daily. Rotate it periodically so that all sides of the plant get exposed to sunlight.

Keep the root zone just barely moist, as an overly wet condition can lead to root rot and/or dying of lower leaves.


Murraya paniculata lacks light for growth

My Murraya paniculata plants stopped flowering a few months ago, even though I use fertilisers regularly. Do such plants produce flowers all year round?

Sheena Goh

This plant has various common names such as orange jessamine, Chinese box, mock orange and mock lime. It is relatively free-flowering if it is grown under full sun and fed regularly.

The reason your plants are not flowering is likely because they are not receiving sufficient direct sunlight for growth. The lack of light is also evident from the rather lanky growth of the plants.


Gunshot holes caused by bagworms

Our 30-year-old jambu ayer tree has had almost all its leaves eaten by a type of pest. The pest sticks on the underside of the leaves and makes circular holes on them. What can I do to eradicate the pest?

Dennis Lee

The tree appears to have been attacked by bagworms, which are larvae (caterpillar) of certain moths.

They build a protective case out of the leaf tissues of the plant they are feeding on. They feed on the undersides of leaves.

When the top portion dries and falls off, it creates openings that look like gunshot holes. Leaves that have been damaged will not recover.

You can use Dipel, an organic, bacteria-based pesticide that is highly effective against caterpillars.

Dipel is derived from Bacillus thuringiensis var. kurstaki, known as BTK for short.


Four Seasons Lime more than a festive plant

This plant started blooming two months ago. I have been told it is a lime plant. Can you help identify it?

Greg Chong

Based on the shape of the leaves and fruit, the plant could be the Four Seasons Lime that is a popular citrus festive plant for Chinese New Year.

Botanically, it is known as x Citrofortunella microcarpa. There are numerous hybrids being created and identification can be difficult as these plants have very similar morphological characteristics.

This citrus can be quite rewarding to grow in Singapore as it can fruit relatively well. The fruit can be harvested and used for various culinary purposes.


Dracaena fragrans affected by growing location

I bought a pot of Dracaena three months ago from the nursery. I have been watering it regularly and giving it epsom salt fertiliser, as directed by the nursery, on a monthly basis. However, I noticed that the leaves are not as green as before. What could be wrong?

Tan Qiu Ling

Your Dracaena fragrans (commonly known as "Tie Shu" or Metal Tree in Singapore) may be placed in a brighter location at home. Under more intense light, the leaves often take on a less green appearance. During production in a nursery, this plant could have been grown under shadier conditions.

Avoid the excessive feeding of magnesium via epsom salts which is essentially magnesium sulphate.

I suggest that you test the soil pH level first with a reliable probe to decide whether you need to feed the plant with magnesium.

• 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@sph.com.sg

A version of this article appeared in the print edition of The Straits Times on December 23, 2017, with the headline 'Root Awakening'. Print Edition | Subscribe