Root awakening: White patches are lichens

White patches are lichens
White patches are lichensPHOTO: CASLIN LEE
Fruit from passionfruit plant is edible
Fruit from passionfruit plant is ediblePHOTO: WILLIAM CHAN
The Vine Spikemoss or Willdenow’s Spikemoss (above) is an attractive spikemoss species that is native to Singapore.
The Vine Spikemoss or Willdenow’s Spikemoss (above) is an attractive spikemoss species that is native to Singapore.PHOTO: WILSON WONG
Scale insects likely cause of spots on lemongrass
Scale insects likely cause of spots on lemongrassPHOTO: STARRY CHAN

White patches are lichens

I found white spots on my frangipani tree. What caused them and what can I do to prevent their spread?

Caslin Lee

The white patches on the trunk and branches are lichens, which grow when the ambient humidity is high. The lichen does not affect the health of the tree as it is a non- parasitic organism.

It is a good indicator of air quality in your garden, as lichens rarely grow in polluted areas.

Fruit from passionfruit plant is edible


I bought this plant from a nursery 11/2 years ago and was told it was a Taiwanese passionfruit plant. It has many flowers, but never produced any fruit. I used a brush to dust the pollen onto the stigma and the plant produced a weird- looking fruit (pictured). Is it edible?

William Chan

The plant is commonly known as the Giant Granadilla. Its botanical name is Passiflora quadrangularis.

Its fruits are edible and one of the largest among passionfruits.

Depending on the variety you have, its flesh may have a sweet- and-sour flavour and can be consumed fresh or enjoyed in drinks.

Tip: Vine Spikemoss' iridescent blue leaves a rarity in plant world

The Vine Spikemoss or Willdenow's Spikemoss is an attractive spikemoss species that is native to Singapore. Its botanical name is Selaginella willdenowii.

The plant is admired for its iridescent blue leaves that are uncommon in the plant world. It has a scrambling growth habit and is best grown in a moist environment with filtered sunlight and protected from strong winds.

Grow it in moist and well-drained soil. This species can add colour to a shady corner of an outdoor garden.

More sunlight needed for Cambodian Dragon Tree


I have had this plant (pictured) for six months and was told it would grow well indoors and need little watering. It is in my common corridor and fertilisers are given monthly. Lately, the leaves turn brown fast. How do I care for this plant?

Chia Kum Khuen

The plant is the Cambodian Dragon Tree. Its botanical name is Dracaena cambodiana.

Make sure you are growing it in a well-lit location - it is not a shade- tolerant indoor plant. It should get at least six hours of direct sunlight and the soil should be kept moist.

The plant should not be allowed to dry out excessively at the roots.

Also, do not apply an excessive amount of fertiliser.

Excessive fertiliser can burn the leaves and roots. To be safe, you can halve the dose recommended on the label.

Scale insects likely cause of spots on lemongrass

I have a lemongrass plant growing in my lawn. It is exposed to full sunlight and rain. Now, there are brown and white spots on the leaves. What caused them and are they harmful? How do I get rid of them?

Starry Chan

The pests on your lemongrass appear to be scale insects. Cut off the badly infested leaves to reduce the population of these pests.

As this is an edible plant, it is best to use less toxic pesticides such as neem or summer oil. These oils suffocate the pests by smothering them.

Apply the oil periodically to ensure the population is kept under control.

Lemongrass thrives best if it is grown in the ground and outdoors under full sun. If it is grown in a pot, the plant will be subjected to stress from a lack of water due to the small root and soil volume. This causes it to be prone to pests and diseases.

•Answers by Dr Wilson Wong, a certified practising horticulturist and founder of Green Culture Singapore ( He is also an NParks-certified park manager.

•Have a gardening query? E-mail it with clear, high-resolution pictures of at least 1MB, if any, and your full name to

A version of this article appeared in the print edition of The Straits Times on October 15, 2016, with the headline 'Root Awakening'. Print Edition | Subscribe