Root Awakening

Rose Painted Calathea needs a more humid environment.
Rose Painted Calathea needs a more humid environment.PHOTO: IVAN TAN
Unhealthy root system of dwarf umbrella tree may cause leaves to drop.
Unhealthy root system of dwarf umbrella tree may cause leaves to drop.PHOTO: KONG WANPEI
Root zone of rosemary plants needs well-drained media and to dry out before watering again.
Root zone of rosemary plants needs well-drained media and to dry out before watering again.PHOTO: FRANCIS CHIA
Water dumbcane regularly to ensure the root zone is moist at all times .
Water dumbcane regularly to ensure the root zone is moist at all times .PHOTO: TOK SOH KHIM

Rose Painted Calathea needs a more humid environment 

I water this plant every two days, but the leaves appear to be drying up. The plant is grown indoors and gets morning sun till around 11am. This is my second plant in four months. The first one withered in the same manner. The nursery repotted this plant when I bought it. I do not see any pests or insects on the plant or in the soil. What is wrong with the plant?

Ivan Tan

The plant is commonly known as the Rose Painted Calathea and its botanical name is Calathea roseopicta. The rolling and drying of leaves is a sign the plant is grown in a location lacking in humidity.

High-rise conditions can be too windy and dry. Excessive sunlight can burn the leaves. Calathea plants require a humid location and they do well under filtered sunlight for four to six hours daily.

Also, check the health of the roots and that the plant is not too deeply potted. Root rot can occur due to prolonged wet feet while crown rot can arise when a plant is planted too deeply. Either case will lead to an unhealthy root system that does not allow the plant to take in water normally.

If there are rotten and dead roots, trim them. Repot the plant with fresh soil, bag it with a clear plastic bag and place it in a cool, bright corner of the home.

The plant may be able to produce new roots later and the plastic bag can be gradually removed to acclimatise the plant to ambient conditions.

Unhealthy root system of dwarf umbrella tree may cause leaves to drop

I recently bought a schefflera. After a week, it started to develop spotty leaves which turned brown and dropped off. Its stalks started to droop too. I water till water drains out from the bottom of the pot. In two weeks, I have been watering it thrice when the top 5 to 10cm of the soil felt dry. The water is from the tap which has been left to stand for one to two nights. I place the plant by the window, which gets the morning sun. It remains there in the afternoon when there is no direct sunlight, but the area remains bright. I rotate its position every few days. I gave it two teaspoons of organic fertiliser a few days ago, but there are no improvements. Why do the leaves continue to drop or develop spots? I cannot see any insects on the plants.

Kong Wanpei

Check if your dwarf umbrella tree (Schefflera arboricola) is well-rooted. Some of these potted plants on sale may be newly rooted and placing them in a sunny area will burn and stress them, leading to the symptoms you have observed.

If the plant is not well rooted, move it to a cooler and shadier spot for it to develop a good root system before acclimatising it to its final growing location.

You may also want to check the health of the root system.

An unhealthy root system will prevent the plant from taking up water properly. The lack of water will lead to wilting of the plant and loss of lower leaves over time.

You may want to cut the stem and root it again if the root system is unhealthy.

Adjust your watering frequency or change the soil to something that is more well-drained to avoid root rot resulting from wet feet.

Finally, the spots may be due to sunburn.

As newly propagated plants may be produced under shadier conditions, the exposure to direct sunlight for your plant may be causing the leaves to be burnt.

While the burnt leaves will not recover, the plant will acclimatise over time and produce new leaves that can take more light.

Root zone of rosemary plants needs well-drained media and to dry out before watering again

This is my second pot of rosemary in two months. I was told by the shopkeeper to water and sun it every day. The first time, I kept the pot in the kitchen toilet to avoid direct sunlight, but it did not survive. This new pot has direct afternoon sun. What can I do to save it?

Francis Chia

Locally sold rosemary plants are often grown in a coco peat-based mix which retains water at the roots.

The root zone has to be allowed to dry out sufficiently before you water again. However, do not allow plants to dry out totally until they wilt. Under tropical conditions, prolonged wet feet will lead to disease in rosemary plants and cause them to die.

The plants should be grown protected from the rain and in a spot which gets four to six hours of filtered sunlight.

Some gardeners have resorted to taking tip cuttings from existing rosemary plants and rooting them to start new plants, which are then potted up in a well-drained growing mix that is more aerated and dries up quickly in the tropics.

Such a mix can be made by mixing two parts of gritty material such as fine expanded clay pellets with one part of compost.

Water dumbcane regularly to ensure the root zone is moist at all times

I have this plant where the leaves at the bottom seem to be drying up. What is wrong?

Tok Soh Khim

The plant is a cultivar of dumbcane called "Galaxy". Dumbcane plants belong to the yam family (Araceae) and are classified in the genus Dieffenbachia.

The drying of leaves may be due to watering issues. Did you allow the plant to dry out totally before? The lack of water can cause the older leaves to dry out.

As such, when growing the dumbcane, it is recommended you keep the root zone moist at all times.

Repot the plant into a larger pot if you find the roots of the plant filling up the existing container. Also, grow the dumbcane in a spot where it can get four to six hours of filtered sunlight daily.

Do note that the plant produces a sap that may irritate the skin of sensitive individuals and no part of the plant should be ingested.

• Answers by Dr Wilson Wong, an NParks-certified practising horticulturist, parks manager and ISA-certified arborist. 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.

A version of this article appeared in the print edition of The Straits Times on February 22, 2020, with the headline 'Root Awakening'. Print Edition | Subscribe