Citronella needs well-draining media

I bought this plant from a nursery a few months ago. I have been watering it once a day and giving it fertiliser once a week. I place it on my balcony, where it is sunny and sometimes windy. However, the leaves keep turning brown. I trim these, resulting in a bare plant. How do I get the plant to grow bushy?

Joe Hioa

The Mosquito Plant (Pelargonium "Citrosum") is not an easy plant to grow as it prefers a cooler and drier climate.

Pelargoniums originate from Australia, the southern African region and the north of New Zealand.

Overly wet soil often causes the lower leaves of the plant to become infected and die. The heat in Singapore can reduce the plant's vigour.

To make the environment more conducive for the plant's growth, grow it in a well-draining media that contains coarse, gritty components such as pumice and fine expanded clay pellets.

The media that is commonly used to grow this plant is often cocopeat-based, which retains too much water.

You may also want to propagate it and grow it in a more suitable media. It should be given sufficient ventilation and direct sunlight for four to six hours daily to thrive.

Compost a source of food for millipedes

In the past month, my garden has been infested by millipedes. Following the recent heavy rain, hundreds of these bugs crawled out of the soil and into my home. Are they harmful to plants and is there any way to get rid of them?

Jonathan Lim

Did you recently apply some compost to your garden? Millipede infestation is a common problem in Singapore because of the compost often sold in nurseries here.

Made from shredded tree branches, the compost is often not mature enough and has high carbon content, making it a source of food for millipedes. The compost may also already have the eggs of millipedes. Existing millipedes in the garden can feed on the newly applied compost and breed.

In large numbers, millipedes are a nuisance to humans and may also consume plant roots and small seedlings.

There is no short cut when it comes to managing millipedes. As the compost slowly matures, the millipede population will gradually decrease. There are chemical pesticides you can use to kill them, but they may be harmful to plants and soil.

You may want to make your own pitfall trap that is fitted with a light source. Bury a container in the ground - deep enough until the rim is level with the soil surface. Fill the container partially with an insecticide mix.

Millipedes will be attracted to the light and fall into the trap where they either drown or get poisoned by the insecticide.

There are online tutorials explaining how to build such a trap.

Creeper plant is a parasite

I saw this creeper plant hanging from a casuarina tree near Nicoll Drive. What is it? The plant has tendrils, but no leaves or roots. How does it get its nourishment and can it be propagated?

Hassan Ali

The plant is a parasite, which obtains its nourishment from its host plant through a sucker-like attachment called a haustoria.

It is hard to identify what parasite it is as the picture is not clear. It could either be the Southern Dodder (Cuscuta australis) or Dodder-Laurel (Cassytha filiformis).

They can be differentiated via their flowers: Southern Dodder flowers are borne on a globose clump while Dodder-Laurel flowers are produced on a short spike. They grow from seeds.

Butterfly pea plant lacks sunlight

Why does my butterfly pea plant not flower?

Chong Moi Thye

The plant could be suffering from a lack of sunlight. The butterfly pea plant (Clitoria ternatea) grows best under full sun to thrive and flower.

In an apartment, ensure that the plant is exposed to at least four hours of direct sunlight daily.

Prune affected leaves of curry tree to get rid of pests

My curry tree plant is infested with pests, which are found on the underside of the leaves. How do I get rid of them?

Vivien Khoo

The larvae of the Tortoise Beetle (Silana farinosa) are commonly found on the curry tree (Bergera koenigii). These larvae have a unique protective covering made from debris, discarded skin and faeces.

The easiest and safest way to remove them is to prune affected portions promptly. Check the plant regularly and remove pests when you see them so that damage can be prevented early.

•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