Yam bean may not grow well in compacted soil

I got seeds from a turnip plant and planted them. I grew two plants, about 50cm apart, and the leaves appear normal but the tubers look abnormal. What is the reason?

Kong Wah Beng

The plant with the edible underground tuber shown in the picture is botanically known as Pachyrhizus erosus. It is commonly mistaken for the turnip and should be correctly called the yam bean.

The tuberous root not developing ideally could be due to compacted soil that is rich in clay and with little organic matter. You may want to improve the soil structure by adding organic matter like mature compost.

Chilli plant infested by spider mites

What pests are infesting my chilli padi plant? What are the treatments available?

Adrian Ling

Your chilli plant seems to be infested by spider mites, which appear as small reddish dots. Their feeding habit will cause leaves to develop small yellow dots that coalesce into larger yellow patches.

Summer oil is a suitable pesticide that can be used to manage a spider mite infestation. Spray all parts of the plant as thorough coverage is needed to suffocate the pests. Repeated weekly applications, for a start, are required to manage the pest population and minimise plant damage. You can also routinely gently wash your plant whenever you water it to dislodge pests from the plant. Ensure your plant is given sufficient sunlight and water throughout its growing cycle.

Different fruit tree species, different growing methods

I would like to know more about growing fruit trees. How do I fertilise or treat the plants to encourage fruiting while keeping them short? What else can I do besides fertilising?

For fruit trees which are potted or grown in the ground, how do I keep them short, about 2m tall? Is it possible for durian, rambutan and mango trees to fruit if they are constrained? How do gardeners treat their plants to fruit in pots?

Fonzie Teo

Fruit trees vary in terms of their growth habits and management regimen, depending on the species. In general, fruit trees, when grown from seed, need to be given space outdoors and time, where they will grow quite large to attain reproductive maturity before they start to flower and fruit.

It is, therefore, not practical to constrain seed-grown trees in pots with constant pruning to keep them small and expecting them to fruit.

Horticulturists and farmers devised the grafting technique to obtain plants that can flower and fruit at a much smaller size. This involves taking a mature flowering and fruiting branch and grafting it onto a rootstock. This has been done with many popular fruit tree species, such as jambu, lemon and mango.

Grafted specimens can be grown in large pots to constrain their size and will flower when the season arrives.

Do note that if a grafted plant is planted in the ground, it has the potential to grow into a large tree.

You can consider precocious fruit tree species that flower and fruit at a young age and at a smaller stature. These include papaya, guava, soursop and custard apple and are a more practical choice for small Singapore gardens. Depending on the variety, they can grow to 2m to 3m tall.

Plant could be a weed from the aroid family

What’s the plant growing from my pot of fern? Some of my other potted plants also have that. I think it came with the potting mix I used.

Andrew Wong

The plant shown in the picture appears to be a Typhonium species which belongs to the aroid family (Araceae). It features an underground corm and grows as a spontaneous weed in local gardens, on roadsides and in open fields. 

In Singapore, three species – namely, Typhonium trilobatum, Typhonium roxburghii and Typhonium flagelliforme – have been observed. At present, the identity of the plant you have cannot be easily discerned at the juvenile stage. Features like the mature leaf shapes and flower characteristics are needed to distinguish the species.

Ferns can grow big and compete for resources

My water jasmine is more than a decade old. A year ago, a small fern started growing at the base of the plant. I left it alone and now it has become a huge fern. Will it harm my water jasmine if I leave it alone? Should I try to remove it?

Teo Chia Hsia

The ferns that are growing at the base of your water jasmine (Wrightia religiosa) are bird’s nest ferns (Asplenium nidus). As the fern-water jasmine combination can appear messy to some people, you may want to remove the ferns now while they are small. It will also be an easier task to perform. You can plant the ferns in separate pots if you want to keep them.

The ferns will grow much larger in time. Its fronds will shade out the water jasmine and there will be competition for water and nutrients. Their roots will get intertwined as well. It will become more difficult to separate the plants later on without causing damage to the roots of the water jasmine.