Spots on leaves are a sign of injury

My snake plant’s leaves have some brown spots. What are they? I recently applied Confidor on the plant.

Adrian Ling

Did the spots appear after you sprayed the pesticide on your snake plant (Dracaena trifasciata)? Pesticides may damage leaves if the dosage is too concentrated or applied during hot weather. Try applying a more diluted version during the cooler part of the day. Spray on a small part of the plant to test the effects before spraying the entire plant.

Another cause could be exposure to rain. Rain can injure the leaves and pathogens in the environment can infect the site, causing spots to appear.

This plant may grow better under a shelter to protect it from the elements, provided it is still exposed to some sunlight. A lack of sunlight can lead to soft, floppy growth and vulnerability to disease. Ensure there is proper air circulation as well.

Bonsai needs sunlight to thrive

The leaves on the lowest branch of my plant are turning brown, though those on other branches are green and healthy. What is wrong?

Yeo Khoon Kee

Your bonsai looks like a Juniperus, which is a sun-loving species that needs direct sunlight for at least six hours a day. A shaded location such as that shown in the picture is not suitable, as the lack of light will kill the leaves.

Also, ensure that the soil is neither too compacted nor too clay-like, as roots that are too wet or dry will die and be unable to take up water. Wet feet can also lead to disease.

In an apartment setting, which is not as sunny as the outdoors, the root zone may not dry out quickly enough, so you may need more aerated and well-draining soil.

Pineapple plants fruit only once

I have pots of pineapple plants, one of which (pictured) has not fruited for nearly two years. How long does a pineapple plant take to bear fruit and can it do so again after being harvested? Are there pineapple plants that do not bear fruit at all?

Lim Gail

Most pineapple plants are expected to fruit when they are at least two years old. Some may take longer, depending on the cultivar and growing conditions. Note that each pineapple plant flowers and fruits only once in its lifetime.

After the fruit is harvested, the plant will stop growing and suckers will appear between the leaf axils. Once large enough, these suckers can be separated from the mother plant and planted separately.

Baby rubberplant is a common houseplant

What plant is this and is it flowering?

Shia Yang Lik

Your plant is commonly known as the Baby Rubberplant (Peperomia obtusifolia) and it is indeed flowering. It is a common foliage houseplant and has several different cultivars with variegated leaves.

This plant is best grown in well-drained media under filtered sunlight and should be allowed to dry out slightly between watering sessions, as wet feet can cause the rest of the plant to rot.

Ensure rosemary gets enough light

What is wrong with my plant and how do I fix it?

William Teo

Your rosemary (Salvia rosmarinus) needs to be grown somewhere sunny. This herb does not thrive in a shaded spot. Ensure that all parts of the plant, including the base, are exposed to sunlight – rotate the pot periodically if you are growing it in an apartment.

Keep the surface of the soil dry. Water the plant thoroughly each time and let the root zone dry out slightly before watering again. Moist or wet soil around the crown can cause the lower leaves to rot and die.

• Answers by Dr Wilson Wong, an NParks-certified practising horticulturist and parks 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.
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