Chewed leaves, yellow spots on jasmine plant caused by pests

What is the name of this plant (above) and what is happening to it?

E.C. Ong

The plant is likely the jasmine (Jasminum sambac). There appears to be at least two pest issues affecting the plant.

First, there are large chewed portions on the leaves. They could have been inflicted by pests such as grasshoppers and beetles. You have to monitor the plant closely to pinpoint the exact pest or pests that caused the damage. Note that some of them are nocturnal.

An appropriate control measure can be recommended only when the pest causing the damage has been identified.

Next, there are numerous tiny yellow spots on the leaves. They could be caused by small sucking pests such as spider mites, whiteflies and/or thrips. They suck sap from the plant, causing it to weaken over time.

The population of these pests can be managed by regular applications of summer oil or neem oil.

Firebush can be propagated via stem-cuttings

I grew this plant (above) many years ago after reading this column. What is it and how do I propagate it? Its flowers attract butterflies.

Ray Ming Chan

The plant is known by a number of common names, including Firebush, Scarlet Bush and Firecracker Bush.

Its botanical name is Hamelia patens and it can be propagated via stem-cuttings.

This plant needs to be grown under full sun and in moist, well-drained soil.

The variegated version of this plant has highly attractive leaves splashed with patches of cream against a green background.

Tips to grow herbs and vegetables successfully

I have been trying to grow herbs and vegetables. I bought soil and organic vegetable fertilisers from HortPark's Gardeners' Day Out events. However, my plants are small, the leaves are brown and dried and the flowers on my lady's finger drop off. What can I do to grow herbs and vegetables successfully?

Esther Toh

Poor growth of plants can be due to myriad factors.

First, ensure you have sufficient sunlight to grow your plants. In an apartment, edible plants would generally need four to six hours of direct sunlight daily to grow well. Some edible plants need an entire day's worth of direct sunlight to thrive.

The stunting of plants could be due to the lack of nutrients available for plant growth. A number of factors may contribute to the issue you faced.

One factor would be incorrect soil pH level, which leads to nutrients in the soil being locked up. You can measure the soil pH level using a soil pH probe and make the appropriate corrections.

Another factor could be the quality of ingredients used to make the soil mix. For instance, if compost that is not mature is used, it could draw nitrogen away from plants in a process called "nitrogen draw down", causing them to turn yellow and exhibit poor growth.

Finally, organic fertilisers, in general, do not contain the whole range of nutrients plants require for growth.

Also, nutrient levels tend to be low in organic fertilisers. Regular applications of a range of organic fertilisers are often required to ensure plants get the nutrients they need for robust growth.

Move root ball intact when repotting plant

I repotted my avocado plant (above) two weeks ago into a bigger container with new soil bought from a supermarket. After three days, the plant began to wilt. I watered it minimally and placed it under the sun, but its condition remained the same. After a few more days, the leaves started to turn brown as if they were burnt. What happened to my plant and can it be saved? The condition does not affect my other plants.

Branden Mohammad

When you were transplanting the avocado plant, did you ensure the root ball was moved intact?

If a lot of soil had fallen off the root ball, the roots of your plant may have been damaged. As a result, transplant shock would have occurred and the plant will not be able to absorb water properly. Subsequently, the plant wilts and leaves get damaged when it is placed under the sun.

For now, you may want to move the plant to a bright and cool location. Wrap the entire pot together with the plant with a clear plastic bag to reduce water loss. Ensure the soil is moist and does not dry out. Such an environment will allow the plant to recuperate.

If the plant improves, you can see leaves perking up and some growth. Once that happens, open the bag gradually and expose the plant to brighter light conditions over a period of two to three weeks to allow it to acclimatise to the environmental conditions of its final growing location.

Also, from the appearance of the leaves, it appears that your plant is suffering from a nutrient deficiency. The leaves are chlorotic, where the veins remain green against a largely yellow background.

Test the soil pH level, namely the acidity or alkalinity, to ascertain if it is in the right range for growing your plant. When the soil pH level is not in the right range, nutrients get locked up and become unavailable for absorption by your plant.

Lemon plant growing on calamansi lime may need to be pruned

I have a calamansi lime bush in my garden. There is another plant (above) growing from the base of the calamansi lime. This outgrowth has a lighter-coloured stem and bigger leaves. It probably belongs to the citrus family because it has thorns and the leaves, when rubbed, emit a citrus-like fragrance. What is the name of this plant? Does it bear fruit and, if it does, is the fruit edible?

Mah Yoke Yoong

The shoot that sprouted from the base of your plant is likely that of the lemon plant (Citrus x limon).

The lemon plant is often used as a grafting rootstock for many types of citrus species. Lemon rootstocks confer vigour to plant materials that have been grafted on them. They appear to also provide some tolerance to waterlogged soils.

You should prune the lemon portion if it gets too large as it may overtake the growth of your calamansi lime.

• 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