Plants too close to each another

A few months ago, I planted Jatropha integerrima and Murraya paniculata plants next to each other. I pruned them regularly to encourage denser growth. I noticed the Jatropha integerrima grows faster and taller than the Murraya paniculata. Are there any advantages to growing different species of plants side by side?

Sheena Goh

From your pictures, the plants may be planted too close to each other. Your Jatropha integerrima plants are blocking sunlight from your Murraya paniculata plants.

As your plants are grown in a sheltered area where sunlight comes from only one direction, move the planter box so that the plants are exposed to the maximum amount of sunlight. Space them out well so that they do not block each other.

Different plants have varying growth rates. Some gardeners like to grow a range of plants together mainly for aesthetic reasons.

A mixture of plants can provide a visually attractive contrast of leaf textures, colours and growth forms. However, this needs to be done carefully, taking into account each plant's growth rates and requirements. Competition can do more harm than good.

However, companion planting may help to deter certain pests from particular plants.

Hand-pollinate soursop plant to encourage fruit growth

I bought a small soursop tree from a nursery about five years ago and planted it in my garden. I watered the tree and added fertiliser to the ground. About two years ago, I found two small fruit growing, when the tree was about 4m tall. Many flowers started growing after, but they eventually shrivelled and dropped. Since then, there has not been any fruit. What happened?

Philip Tan

The lack of fruit could be due to the lack of pollinators in the urban environment. In this case, consider hand-pollinating to encourage fruit to grow.

You will need to learn to identify the parts of the soursop flower before attempting hand-pollination. Soursop flowers are different from typical flowers - the stigma of each flower is not receptive until after the pollen has been shed.

The soursop flower sheds pollen in the evening, when the flowers first open. Collect the pollen and store it overnight in a refrigerator. The stigma should be receptive by the following day. Dab a fine artist brush with some pollen and dust the sticky part of the flower's stigma to transfer the pollen.

Beetles are known to pollinate soursop flowers. It is best not to use a large amount of chemical pesticides to control pests. Mosquito fogging may also be detrimental in this case.

Ensure the tree is well-watered as the lack of water any time during fruit development can lead to the abortion of young, developing fruit.

Water Hyssop needs to be constantly moist

I have had this plant for about a year. Recently, its leaves turned brown. The pot sits on my porch, where the plant gets the full sun all day. Why does this happen?

Yap Hwee Pin

The plant you have has various names, such as the Giant Red Bacopa, Lemon Bacopa and Water Hyssop. Its botanical name is Bacopa caroliniana.

This aquatic plant can grow wholly underwater or as a marginal plant, where its roots grow in moist or wet soil next to a water body. It grows best when it gets full sun.

The leaves of your plant could have turned brown because it is getting insufficient water. The plant might have dried out because of the hot weather.

Its roots have to be constantly moist, so try immersing them in some water. To prevent mosquitoes breeding, you can add anti-mosquito granules or small fish in the water.

Hawaii Woodnettle has stinging hairs

Is this plant a weed?

Freda Tee

The plant is botanically known as Laportea interrupta (above). Its common name is Hawaii Woodnettle.

It grows as a small shrub, often as a weed in garden beds outdoors. Sometimes, its seeds land randomly in flower pots.

The top part of the plant has stinging hairs, so wear gloves if you have sensitive skin and need to remove the plant from the pot.

Strawberry plants need at least four to six hours of filtered sunlight

The leaf tips of my strawberry plants dried up before they died. I watered them once every two days. They were placed near a window that has bright, though not direct sunlight. What happened?

Henri Tan

The probable reason for the burnt leaf edges could be a lack of calcium for plant growth. You may want to spray a diluted water-soluble fertiliser that has calcium in it on the leaves.

Follow the directions on the label of the fertiliser bottle to avoid damaging the leaves.

Also ensure the strawberry plants are not in an area that has particularly low humidity or is windy. They should also get at least four to six hours of filtered sunlight. The lack of sunlight can render the plants weak and susceptible to diseases. Soil that is often soggy can cause the plants to rot.

• 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