Palms may have fungal disease and nutrient deficiency

I have had two pots of red palm in my garden. They were both more than 20 years old. One plant grew very quickly and became about 10m tall. The other was transplanted from a vase and, until today, remains quite small. The big palm started to dry up and die from a disease several months ago. The small palm, which was grown about 4m away, seems to be suffering from the same disease. How can I save the palm and "sanitise" the soil in my garden?

Philip Lim Yoon Hock

Your sealing wax palm (Cyrtostachys renda) may be affected by a fungal disease called the Ganoderma butt rot. A confirmation of an infection is the appearance of fungal fruiting bodies that resemble the common lingzhi fungus and affected stems will show an internal discoloration when cut.

This fungus resides in the root zone and there is currently no effective way to manage the disease. As the fungus survives in the soil, planting another palm in that same location is not recommended. It is best to practise "crop rotation" by planting another unrelated plant species in the affected site.

For your surviving palm, the yellowing of fronds points to a nutrient deficiency. From the picture, it appears that your palm is lacking in potassium. It is a nutrient that is not held by the soil and easily leached during heavy rain.

Start a fertilising regimen that provides more potassium for your palm on a regular basis. New leaves should appear green later on.

Your palm is also probably under moisture stress. It needs to be well watered and organic mulch should be applied around the base of the palm to conserve moisture.

Monstera affected by fungal disease

There are brown spots on the underside of a few leaves on my monstera plant. The leaves are also slightly yellow. What is causing the brown spots and what can I do to prevent them? The plant is kept indoors in an area with at least four to six hours of indirect sunlight daily and watered thoroughly once a week.

Y.M. Ng

A fungal disease is likely to be affecting your plant. If it is just a leaf that is infected, you can prune and discard it with your household trash.

Ensure that the plant is receiving sufficient sunlight and air circulation. The lack of light and moist conditions can lead to fungal infections.

Protect Amazon Elephant's Ear from drying winds

Why do the leaves on my plant look burnt?

Choo Kim Lai

The plant is commonly known as the Amazon Elephant's Ear (Alocasia x amazonica).

There are a number of reasons for the symptom. If it is an old leaf, it is normal for it to turn brown because it will eventually be shed by the plant.

If there are new leaves that look normal, then there is no cause for concern.

This plant is sensitive to a dry and sunny environment, which can cause leaves to exhibit burnt symptoms. It is best grown in a semi-shaded location where it is protected from drying winds.

You will probably need to grow several plants around it to provide a more humid micro-climate.

The soil used to grow this plant should be kept moist. It should not be allowed to dry out and do not over-fertilise it.

Malayan Eyebright and Pepper Elder occur as weeds

What are these two plants?

Andrew Wong

Both are common plants that occur as weeds in flower pots and garden beds.

The first plant is commonly known as Malayan Eyebright and its botanical name is Legazpia polygonoides.

The second plant is commonly known as the Pepper Elder and Common Peperomia. It is botanically known as Peperomia pellucida. It is sometimes harvested and consumed as a salad vegetable and has medicinal properties too.

Hibiscus has iron deficiency

What is wrong with my plants? The one on the right looks less healthy than the one on the left.

K.L. Goh

Your hibiscus plant appears to be suffering from iron deficiency, which is very common in Singapore.

The common cases for iron deficiency can be due to alkaline soil and soil that is compacted and hence not well-drained. You will need to check the pH level of your soil using a soil pH test kit.

Alkaline soil can be correctedwith the addition of sulphur into the soil, but the process can be slow. Good quality organic matter can also be added to help improve drainage and aeration in the soil for healthy roots.

At the same time, you can look for water-soluble fertilisers that have chelated iron for easier absorption by the plant, which temporarily alleviates the symptom.

• Answers by Dr Wilson Wong, an NParks-certified practising horticulturist and park 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