Sweet potato likely infested with spider mites

The leaves of my sweet potato plant have white patches. What is the cause? Are the leaves still edible?

Goh Xun

Your sweet potato (botanical name: Ipomoea batatas) may be infested with spider mites. The yellow dots and patches may be a result of the sucking damage caused by these pests. Turn a leaf over to check if there are spider mites, which appear as very tiny red dots.

The damaged leaves are safe to eat.

The most environment-friendly way to deal with this is to prune and discard the infested portions.

As the plant produces new growth, mist it regularly to keep the environment humid and to wash away spider mites and their eggs. This can help to keep the population in check.

You may want to spray summer oil or neem oil if the infestation worsens. These oils need to be applied thoroughly on all parts of the plant to suffocate existing pests.

If you do not see spider mites, the yellowing may be due to a nutrient deficiency. Ensure the soil is well-draining and the pH level is between 5.6 and 6.5 so that nutrients are available for the plant. Keep fertilising your plant as it grows.

Also, make sure it is grown in a sunny spot so that it is in good health and can deter pests from attacking it.

Common Bauhinia grows into a large woody climber

I found this interesting-looking plant in the nature reserve. What is it?

Andrew Wong

The plant is botanically known as Bauhinia semibifida and is commonly known as the Common Bauhinia.

It is a native plant of Singapore and can be seen growing in the nature areas. It grows as a large woody climber. The silver marking on the leaves tend to occur in younger plants and disappears as the plant grows larger and matures.

Indian Spurge Tree, Bird's Nest Sansevieria may need repotting

I plucked a small piece of this plant (left photo, above) from my mother's home more than five years ago and it has grown. But now, part of it is grey and brown. Is it dying? Also, another plant grew (left photo, below) beside the first one - what is it and should I repot it? My third plant (right photo) was given to me and it has grown so fast, the long pot is now full. What is its name? These two pots are placed on the small balcony outside my hall and they get afternoon sun.

Sandra Kuah

In the left photo, the plant at the top is the Euphorbia neriifolia and its common name is Indian Spurge Tree.

Next to it is a Bird's Nest Fern (botanical name: Asplenium nidus).

The latter is fast taking over the pot and should be promptly removed if you want to keep the Indian Spurge Tree.

The reason the Indian Spurge Tree is declining could be due to the competition with the Bird's Nest Fern.

The latter's roots grow fast and could be robbing the Indian Spurge Tree's water, nutrients and space to grow.

After you remove the fern, check the soil below to see if this is the case. You may have to remove all the fern's roots and pot the Indian Spurge Tree up with fresh soil.

In the right photo, the plant is the Bird's Nest Sansevieria. Its botanical name is Sansevieria trifasciata and this particular cultivar is called Hahnii.

The plant prefers to be grown in a well-draining mix and under good light to develop a stout-looking rosette with rather firm leaves.

It spreads by sending up suckers, which eventually grow and fill a pot.

What you can do is to carefully take the plant out of its pot, divide it into several sections and pot them accordingly.

Amazonian Elephant Ear grows best in semi-shade

What is the name of this plant and how do I take care of it?

Irene Sng

The plant is botanically known as Alocasia amazonica and its common name is Amazonian Elephant Ear. The brown patches on its leaves are caused by sunburn due to exposure to direct sunlight.

The plant is best suited for growing under semi-shaded conditions. In an apartment setting, it grows best when it gets at least four hours of filtered sunlight.

It needs a well-draining, aerated and moisture-retentive growing mix.

If a soil-based media is used, the media needs to be amended with lots of organic matter such as peat moss, which retains moisture, and coarse gritty material, which helps to open up the mix so the roots of the plant do not experience prolonged wet feet. Wet feet can cause the roots and crown of the plant to rot.

Tembusu tree produces scented flowers

There is a lingering fragrance when I run past this stretch of the park connector. This particular tree is in full bloom. Is the scent coming from it?

Ng Tze Yik

The tree is the Tembusu (botanical name: Cyrtophyllum fragrans). It is a slow-growing, evergreen tree that is native to Singapore. Its flowers are scented and when they open, they are pale yellow or cream in colour and turn orange-yellow as they age. The tree yields durable timber.

There are several Tembusu trees listed as Heritage Trees in Singapore. To find out more, go to the National Parks Board's Heritage Tree Register (bit.ly/2Kr89gF).

The most famous Heritage Tembusu tree is perhaps the one shown at the back of the Singapore $5 note that is typified by its almost horizontal, low-lying branch. The tree can be seen in the Tanglin Core of the Singapore Botanic Gardens.

• Answers by Dr Wilson Wong, an NParks-certified practising horticulturist and park manager. He is the founder of Green Culture Singapore and an adjunct assistant professor (Food Science & Technology) at the National University of Singapore.

• 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. We reserve the right to edit and reject questions.