Root Awakening: Yellowing leaves may point to heat stress

Yellowing leaves may point to heat stress

I bought a bread flower plant from a nursery three weeks ago. It was repotted at the nursery and I placed the pot on an open-roof terrace, which gets plenty of sun. I water the plant once in the morning. However, a few leaves turned yellowish- brown recently (below) and started falling. What happened?

Tan Hock Eng

It is likely your plant is still getting used to the new environment, which is vastly different from the nursery where it was propagated.

It is also recovering from the transplanting process. The yellowing of a few lower leaves is usually not cause for concern.


PHOTO: TAN HOCK ENG

Do take note of the concrete surface of your roof terrace. The material gets hot during the day and at night, and the surface radiates heat back into the environment.

The yellowing leaves could be a sign of heat and moisture stress even though thorough watering is done in the morning.

If the soil dries out by the end of the day, you may need to water the plant a second time.

Also, consider taking the pot off the ground and placing it on some bricks instead; and mulching the soil surface to help retain moisture and cool the root zone.

Growing the plant under light shade can also help reduce the amount of stress your plant experiences.


More sunlight needed for plant


PHOTO: JOHN KENNETH CHARLES DAVIES

What is this plant (above)? A few months ago, I moved it from a spot on the balcony that was getting partial sunlight to a more shady area inside. I moved the plant as the leaves started falling and it looked weak. But this did not help. I use a loose potting compound and a diluted nitrogen-based fertiliser about every 10 days.

John Kenneth Charles Davies

It is difficult to identify this plant without its flowers. It could be a type of Lipstick Vine which belongs to the genus Aeschynanthus and is a member of the African Violet family (Gesneriaceae).

Your plant is reacting to a lack of sunlight. In an apartment, sunlight is available only for several hours daily. Once the sun moves, the growing area is in the shade.

Depending on the species you are growing, it may be good to expose your plant to as much sunlight as possible. However, do ensure that the leaves do not get sunburnt.

In your case, you may want to expose your Lipstick Vine to at least four hours of filtered sunlight daily to promote healthy growth.

Also, ensure your plant is kept moist at all times - the Lipstick Vine does not like its roots to dry out completely for prolonged periods.


Elephant Apple's fruit reportedly edible


PHOTO: BEN LEE

What is this tree (above)?

Ben Lee

Its botanical name is Dillenia indica and it is commonly known as the Elephant Apple tree. The tree can be found in some parks in Singapore.

It is a relative of the common Simpoh Air, a shrub that grows in the sunny portions of Singapore's nature areas.

The large fruits of the Elephant Apple tree are reported to be edible and used as an ingredient in Indian curries.


Purple Simpoh shrub can grow to a 25m-tall tree


PHOTO: YEU ENG KIONG

What is this plant (above)?

Yeu Eng Kiong

The plant is likely the Purple Simpoh, which is also known as Simpoh Inggu and Simpoh Lak. Its botanical name is Dillenia excelsa and it is a native plant of Singapore.

It produces attractive yellow flowers and is available in some Singapore nurseries as a shrub.

With time and space, it can grow into a tree of up to 25m. It is a mid- canopy tree that grows in rainforests, occurring mainly in sunny areas with wet soil, such as freshwater swamps and riverbanks that flood periodically.


Tip: Banana shrub produces fragrant flowers


PHOTO: WILSON WONG

The banana shrub (above, its botanical name is Magnolia figo) is a shrub that has a moderate growth rate and a compact growth habit. Its flowers, which develop within fuzzy, brown bracts, have a sweet, banana-like scent. Flowers are produced sporadically.

The plant is widely cultivated as an ornamental plant in fragrance-themed gardens for its scented cream-white flowers. It thrives under full sun and the soil it is grown in should be moist and well drained.


• Answers by Dr Wilson Wong, a certified practising horticulturist and founder of Green Culture Singapore (www.greenculturesg.com). He is also an NParks-certified park manager. He will speak about growing succulents, starting a miniature garden and more at the Singapore Garden Festival this month. General admission to the festival applies (go to www.singaporegardenfestival.com).

• 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

A version of this article appeared in the print edition of The Straits Times on July 16, 2016, with the headline 'Root Awakening'. Print Edition | Subscribe