Plant is likely a Euphorbia hybrid

My plant has not flowered since I bought it two years ago. What is it and how do I get it to flower again?

Pamelin Ho

The plant is likely a Euphorbia hybrid from the Poysean series. To encourage the plant to flower, put it in a sunny spot and withhold watering. If it is given plenty of water and shade, the plant produces large, fleshy leaves in abundance.

Avoid feeding it with a nitrogen-rich fertiliser, as this encourages the production of foliage over flowers.

Lavender plants cannot be saved 

When I bought these lavender plants, they were lively and green. I transferred them into bigger pots without removing their original soil, and topped up with new potting mix. I keep them by a window where they get a lot of sun, and water sparingly. Both plants are drooping and brown leaves are appearing. What is wrong? Can I salvage the plants?

Jeffrey Chua

Lavender plants sold in local nurseries are grown in an organic matter-based growing mix which retains a lot of moisture. This can cause plants to experience wet feet and they will succumb easily to disease, which will rapidly lead to plant death.

Your plants cannot be saved. Should you buy another potted plant, try propagating new plants by taking stem-cuttings. Use a growing mix that is more porous, such as one that contains equal proportions of fine expanded clay pellets, perlite and vermiculite. However, the ratio of ingredients can be adjusted according to your growing conditions. 

Ensure your plants get at least four hours a day of direct sunlight with adequate air circulation. Water them thoroughly and let the root zone dry out slightly before watering again. Sunlight exposure and root-zone moisture management are essential for growing lavender successfully in the tropics.

Longevity Spinach could be infested with pests

Why are there yellow spots on my Longevity Spinach’s leaves? Can they still be eaten?

Megan Chen

The leaves of your Longevity Spinach may be infested with sap-sucking pests, possibly scale insects. You can use your fingernail to try to scratch the spots off. The affected leaves do not look palatable and should not be eaten.

Prune the affected leaves and spray your plant thoroughly with summer oil. This pesticide will suffocate any remaining pests, and repeated applications are required to keep the population in check. Observe the withholding period – the duration that needs to elapse after pesticide application before plant parts can be harvested and safely consumed.

Do not allow aloe vera to dry out

I bought this aloe vera from a nursery, where it had been kept outdoors with no protective shelter. The tip of one leaf appeared flat and reddish-brown at the time, and has stayed that way even after several days. I keep the plant indoors by a north-facing floor-to-ceiling window with plenty of direct sun. Can the browning leaf recover or should I prune it?

Sam Yeo

Although the aloe vera plant is drought-tolerant and rots easily if the root zone is kept moist, it should not be left dry for long periods. This will cause the older leaves to dry out and die, which is starting to occur in your plant.

Water your plant thoroughly each time, to the point excess water flows out from the drainage holes found at the base of the pot. Allow the root zone to dry out slightly before watering again.

The aloe vera is a sun-loving plant and should be located in a spot with direct sunlight for at least six hours daily if you are living in a high-rise apartment.

Inspect plants at night for pest activities

My Alternanthera and Coleus look like something is feeding on them. I have checked day and night, but there are no signs of any pests. I have been spraying the plants with chilli padi mixed into dish soap for about a week, but the pest appears to be doing more damage. What could it be and how should I treat the plants?

Also, how can I help my frangipani tree flower again?

Tan Mei Lin

The bite marks on your Alternanthera and Coleus could be due to pests feeding on the young developing leaves before they unfurl. Some chewing pests are small and active only at night, so it is essential to inspect plants during different times of the day. You may want to install a yellow sticky trap to monitor for pests. Also, your chilli concoction may not be an effective deterrent for pests, as it will be washed away when watering.

The absence of flowers on your frangipani could be due to a lack of light. It is a sun-loving plant and needs to be grown in a site with plenty of direct sunlight, though this can vary depending on where in your garden the plant is situated. The growing site may be in shade, depending on the time of year.

• 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.