Root Awakening: Xiao Bai Cai infested with mites
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Roots that are too dry or wet can be prone to pest attacks.
PHOTO: MELVIN CHAN
Wilson Wong
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Use summer oil to get rid of spider mites
I have been growing organic xiao bai cai in mixed cocopeat soil, but recently noticed silvery white spots on the bigger leaves. I have checked the bottom of the leaves and found no insects. I fertilise once a week and water sparingly once a day. What is wrong?
Melvin Chan
Your vegetables seem to have been infested with spider mites, which are sap-sucking pests that appear as small dots. Use summer oil, which is available at local nurseries, to suffocate them. Repeated and thorough applications of the pesticide are required to keep the pest population in check.
Ensure your plant is not suffering from moisture stress. Plants with roots that are too dry or wet can be prone to pest attacks.
Euphorbia cannot be propagated via stem cuttings
This plant is a perennial and can grow for many years.
PHOTO: ADRIAN LING
My cactus is flowering. What is its expected lifespan and how can I propagate it?
Adrian Ling
Your plant is likely Euphorbia flanaganii, commonly known as Transkei Medusa’s Head. It is a perennial and, if well taken care of, can grow for many years.
This plant cannot be propagated via stem cuttings. You will need to pollinate the flowers and obtain seeds to grow into new plants that will develop the same radial, sprawling growth form.
Dwarf Yellow Mussaenda is a common shrub
This shrub is commonly planted in local landscapes.
PHOTO: TAN PIN HO
I spotted these flowering shrubs in Yishun. Under many clusters of small yellow flowers, there appears to be a pale green leaf. What is this plant?
Tan Pin Ho
This plant is the Dwarf Yellow Mussaenda (Pseudomussaenda flava), an ornamental shrub commonly planted in local landscapes. It produces bright yellow, five-petalled flowers.
The white, leaf-like structure is called a bract, which is a modified leaf.
Thai Dragon Tree needs nutrients
This plant may have to be repotted into a bigger container with fresh soil.
PHOTO: CHEW CHOONG CHEONG
Is this a cabbage tree and will it flower? The leaves are turning yellow. How can I restore their bright green colour?
Chew Choong Cheong
The plant could be the Thai Dragon Tree (Dracaena cochinchinensis). It may be lacking in nutrients if it has been grown in the same soil and pot for a long time.
Check if the growing media is compacted, as this can impede root development and nutrient intake. A pot-bound root system will also lead to frequent drying of the root zone.
In such situations, you will have to repot the plant into a bigger container with fresh soil. Be careful when doing this so you do not damage the roots.
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 . We reserve the right to edit and reject questions.

