The pale green hue suggests a lack of nitrogen.
PHOTO: EDWIN HAN
Wilson Wong
I have been trying to minimise watering my basil plants, leaving them outdoors to get sunlight and rainwater. The plants are still thriving, but the leaves are turning yellow. What is wrong and how can I improve their health?
Edwin Han
The pale green hue of your plants indicates a possible lack of nitrogen. Feed them with a fertiliser containing this nutrient. Nitrogen-rich fertilisers are available in chemical, pelleted or water-soluble forms, and can be bought at local nurseries.
Ensure the soil is well-draining and properly aerated, as well as rich in organic matter. Check that the container has drainage holes at the base, as a waterlogged growing mix will suffocate a plant’s roots and prevent the take-up of essential nutrients.
Succulent is a Kalanchoe
This could be the Lavender Scallops plant, which is native to Madagascar.
PHOTO: ALBERT LIM
What is this plant and which country does it originate from?
Albert Lim
This succulent belongs to the genus Kalanchoe and could be the Lavender Scallops plant (Kalanchoe fedtschenkoi). It is a popular houseplant native to Madagascar.
Give it direct sunlight to maintain its colour and compact growth habit, and keep it in a well-draining growing mix. Water periodically when the mix is dry.
Prune growth from rootstock on grafted plants
If not pruned, the new growth may overtake the Finger Lime plant.
PHOTO: CASLIN LEE
My Finger Lime plant was infested with caterpillars, so I pruned it. It now has two types of leaves: small ones and much bigger ones branching out from a new stem. Why is this so? The leaves smell the same.
Caslin Lee
Your Finger Lime was likely grafted onto a citrus rootstock. Grafting is a propagation method with various advantages, such as a healthier and more robust root system.
The new growth should be pruned promptly to prevent it from overtaking the Finger Lime plant.
Plant is Sulfur Cosmos
The plant’s seeds appear in brown clusters.
PHOTO: VINCENT KOH
I have a plant with bright yellow-orange flowers, but do not recall its name. What is it?
Vincent Koh
This plant is commonly known as Sulfur Cosmos (Cosmos sulphureus). It produces seeds readily, which appear in brown clusters after the flowers fade. You can collect the seeds and plant them separately.
Prune plants regularly to extend their lifespan, as they will slowly die if allowed to produce seeds.
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.
