Lichen is harmless

My old belimbing tree has white spots all over the trunk and branches. What are they and are the fruit still safe to eat?

Audra Ruyters

The grey patches are likely lichen, a combination of a fungus and an algae. It is harmless to you and the tree. It is common to see lichen on older trees growing in moist environments.

Garlic vine needs bigger pot

Avoid spraying new chemicals on plants without first testing them on a small part.

PHOTO: SIN CHEY CHENG

My garlic vine grows up a vertical trellis outdoors. It gets more than half a day’s worth of sunlight and last bloomed in January. How often does it flower?

Recently, its leaves have been turning yellow and patchy, and eventually fall off. I sprayed the plant with a solution of diluted vinegar and orange peels. What is wrong?

Sin Chey Cheng

Did the plant start shedding leaves at a hotter time of the year? If so, it could be due to dehydration and heat stress.

Your plant has limited root space in its current pot, and may lack nutrients. If it has been grown in the same container for some time, it may have used up all the nutrients in the growing mix. 

Avoid spraying new chemicals on plants without first testing its reaction. Some plants may react adversely and their leaves may get damaged. Always test a chemical on a small part of the plant before applying it elsewhere.

You may want to move the plant to a larger pot so its roots have more room to grow. Fertilise and water it regularly, and prune excessive growth periodically to reduce water loss.

The garlic vine usually flowers after a dry spell. In Singapore, this occurs once or twice a year. 

Fiddle-leaf Fig is a slow grower

This plant also looks to be pot-bound.

PHOTO: ADRIAN LING

What is the correct method of pruning this plant?

Adrian Ling 

Grown under optimal conditions, the Fiddle-leaf Fig is a robust species that produces new growth readily when pruned.

Prune your plant at a point high enough that it still has enough leaves to photosynthesise and grow. Some woody plants die when they are cut back to older, bare parts.

This species grows slowly, and the plant will take time to produce new growth. It also appears that your plant is pot-bound and should be moved to a bigger container.

Umbrella tree can be propagated via air-layering

The top half of this plant is producing more leaves as it gets more light than the lower half, which is blocked by a wall.

PHOTO: DANIEL LING

Can I shorten my umbrella tree by cutting off the portion in the photo and replanting the cutting elsewhere? There are hardly any leaves on the bottom half of the trunk and I want them to spread out more evenly.

Daniel Ling

You are correct to propagate a section of your tree to restart as a smaller plant. Stem cuttings can also be done, but thick woody cuttings from your tree may take time to root.

The umbrella tree can be propagated via an air-layering method, also called marcotting. There are numerous instructional videos that you can refer to. Once the propagated section has established a root system, you can discard or give away the original plant.

Your tree’s lack of leaves in its bottom half is likely due to a lack of light at that section, where sunlight is blocked by the parapet wall. Exposure to light is essential for plants to maintain healthy leaves.

Over-pruning a woody plant to an older, bare section can cause it to decline. The plant may not have enough buds if the growing conditions are not optimal or the plant is not strong enough.

Cut the plant in such a way that some leaves are still attached to the original plant, so it can continue to photosynthesise and produce the energy needed for new growth. 

Curry tree seeds can be dispersed by animals

This plant is likely the Gamthi variety of the curry plant.

PHOTO: LEONARD TAN

This plant of unknown origin has been growing in my pot. It seems to be a curry tree, but the branches are pinkish-red, while typical curry branches are green. It has white flowers and green, berry-like fruit which turn black over time.

Leonard Tan

Your description of the plant fits the Curry Tree (Bergera koenigii) – namely, the Gamthi variety, due to its pinkish rachis.

Its fruit turn black when they ripen, and are ready to eat at this stage, but avoid consuming the seeds.

The fruit are eaten by birds and dispersed through their droppings. Your plant may have emerged in your garden through this dispersal mode.

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.

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