Root awakening: Gardening tips

Besides providing food for birds, the pink banana (left) offers a peek into what seeded bananas taste like.
Huge green caterpillars (above).PHOTO: PATRICIA LAI
Iron plant (above).
Iron plant (above). PHOTO: YONG JIA HUI
Besides providing food for birds, the pink banana (left) offers a peek into what seeded bananas taste like.
This plant started out growing well, but the leaves began drooping (above) due to their weight.PHOTO: RICK YAP
Besides providing food for birds, the pink banana (left) offers a peek into what seeded bananas taste like.
Besides providing food for birds, the pink banana (above) offers a peek into what seeded bananas taste like.PHOTO: WILSON WONG

Move caterpillars to protect plant

I have found huge green caterpillars on my periwinkle plants. They can be as long as 7cm and eat a lot of the leaves. Will they grow into moths or butterflies? How do I remove them without harming my plant?

Patricia Lai

The caterpillar is the larvae of the oleander hawk moth. All moths and butterflies have an ecological role in the natural environment.

In this case, to reduce the damage to your periwinkle plant - it belongs to the same plant family as the oleander plant, which is known as the Apocynaceae - you can move the caterpillar to a small fish tank where you can rear it until it pupates and emerges as an adult moth. Then you can release it.

In the tank, you can have controlled feeding, where you can take new fresh leaves from your periwinkle plant to feed the caterpillar. This prevents it from indiscriminately defoliating your plant.

Remember to regularly clean the tank of the caterpillar's waste matter.

Such an activity can be educational, especially if you have young children at home to share with them the fascinating natural world.

Dried-out root zone

I bought this iron plant two years ago.

I water it every day and leave it on the balcony.

But its leaves started to turn yellow and brown. Why is this so and what should I do?

Yong Jia Hui

You may want to repot the plant in a larger container.

At present, the symptoms suggest that the root zone has dried out due to the small soil volume.

It is likely the pot is filled with roots now, with little soil to hold water.

Also, avoid placing the pot in an overly windy and sunny location. This increases the rate of water loss of the plant, leading to the lower leaves of your Dracaena turning yellow and drying out.

It is best to move the pot to a sheltered location where the plant can also be exposed to filtered sunlight for at least half a day.

Lack of light may be reason for droopy leaves

This plant started out growing well, but the leaves began drooping due to their weight. This makes the whole pot look sad and unattractive. Is it normal for the leaves to droop like that and is there something

I can do to improve it?

Rick Yap

The plant is botanically known as Spathiphyllum "Sensation", which is a large form of the Peace Lily. There can be two reasons that may have led to this observation.

First, a plant lacking in sufficient sunlight for growth will exhibit droopy leaves.

Although Spathiphyllum is known to tolerate low light, it does best, and will show more robust growth, if it can get some filtered sunlight for several hours a day.

It should not be placed in a dark corner, deep in the house or behind curtains.

Second, did you recently repot the plant or have not been watering it regularly? Also, check to see if the roots have filled the pot. All these point to the lack of water which can cause the plant to wilt.

When the repotting of a plant is not done properly, its roots will be damaged. When roots of a plant fill a pot, there is very little soil volume to hold water for the plant and it will dry out much more quickly.

Avoid overwatering too, especially if the plant is placed in a dark corner.

Water that does not evaporate quickly enough can lead to overly wet soil conditions which can cause the roots to rot.

The plant will not be able to take in water normally, causing the leaves to wilt as a result.

Hand-pollinate to help fruit set

I have a mature soursop-guanabana tree which was grown from a seed. The tree flowers abundantly. But when the flower blooms, it reveals a tiny fruit covered in numerous black bristles. After some time, the fruit falls off. I have used different types of pesticides. Why does this happen?

K.S. Nathen

The lack of fruit production by soursop plants is probably due to the lack of pollinators in the urban environment. In this case, consider hand-pollinating to encourage fruit set.

Soursop flowers are different from typical flowers as their flowers are described as protandrous - the stigma of each flower is not receptive until after the pollen has been shed.

First, identify the parts of the soursop flower before attempting hand-pollination. Next, collect the pollen from the flower when it first opens in the morning. This can be stored overnight in a refrigerator.

After the stigma has become receptive, dab a fine artist brush with some collected pollen and brush it against the stigma to transfer the pollen.

Dry air in an overly exposed area can also cause fruit production issues. To increase humidity, you can grow more plants around your soursop plant but without shading it, or by installing a misting system. But the duration and frequency of the mist needs to be adjusted to avoid creating an overly wet environment.

Tip: Pink banana a lesson in seeded fruit

Many people grow the edible banana which is seedless. Ornamental bananas such as the pink banana, known botanically as Musa velutina, is a species that produces short and fuzzy fruits with seeds.

The inflorescence has attractive pink bracts - a leaf-like plant part to protect embryo flowers - and appears on upright stalks.

The interesting characteristic of this plant is that when its fruits are ripe, the skin self-peels, revealing the banana flesh inside. The soft, sweet flesh can be eaten but contains many seeds.

It is an interesting plant you can grow in an outdoor garden. It has ecological uses where it can provide food for the birds and can teach urbanites about seeded bananas.

•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.

•Got a gardening query? E-mail it with clear pictures, if any, and your full name to

A version of this article appeared in the print edition of The Straits Times on July 11, 2015, with the headline 'RootAwakening'. Print Edition | Subscribe