Spiders are natural pest control

I often see spiders on my mint leaves. What is causing it and how do I treat it?

Adrian Ling

Spiders do not harm your plants. You should leave them alone, as they are predators of common garden pests.

Their presence is an indicator of a healthy ecosystem in your garden that is free of toxic pesticides.

Nitrogen-rich fertilisers encourage foliage growth

It has been two years and my guava plant has yet to flower. Pruning it resulted in more vegetative growth; spraying it with urea solution resulted in some defoliation. I have tried other methods, but to no avail. How can I get it to flower?

Ho Wai Meng

Ensure your guava plant is growing in full sun and is not in shade during the day. A lack of light will cause it to remain vegetative and not flower.

Do you know the cultivar of your guava plant? If it was grown from seeds taken from a fruit, it will not breed true and it will be difficult to pinpoint its growth pattern and flowering characteristics.

Note that urea is a fertiliser that supplies nitrogen, which will encourage the production of leaves over flowers. Use this sparingly, as it can injure sensitive plants. Instead, try products containing low amounts of biuret.

Guava plants can produce flowers off-season with a brief drought, but do not let the plant dry out excessively, especially since it is being grown in a pot.

You may want to put a concrete slab below the pot to prevent your plant from taking root in the ground. Also note that frequent pruning will make the plant keep producing new growth to replace what was removed.

Do not let olive tree dry out

My olive tree was doing fine with weekly watering until recently. Its leaves have curled and browned over the last three weeks. What is wrong?

Rashmi Krishna

Your olive tree seems to be grown in a pot. During hot and dry weather, this plant will need to be watered more regularly. A plant grown in a small pot will dry out much faster than a plant in a bigger pot, as the larger container holds more soil and retains more water.

When a plant dries out, its roots will become damaged or die, and the plant will be unable to take up water. When this happens, the aerial parts of the plant will dry out as well.

Check if the branches are still alive by bending them gently. If they snap easily and feel dry inside, the branches are dead and should be discarded. Do this with the rest of the plant until you reach live tissue, which is pliable when gently bent. 

Kokedama contains Asian bayberry

What is this plant? I was told it needs only a little water.

Lim Lay Nah

The seedling in your kokedama (ball of moss-covered soil) is the Asian bayberry, botanically known as Nageia nagi. It is a slow-growing species and will eventually become a tree with a tiered conical canopy that can be seen in local parks, gardens and streets. 

You may want to move it into a pot of soil. The growing mix should be well-draining and moist, and the plant will need at least six hours of direct sunlight a day. Under sunny conditions, ensure the plant has enough water and is not allowed to dry out.

Tree is covered in dragon scales

I have lost two trees to this parasite weed. How can I save the remaining tree?

Lim Hui Lian

Your tree is covered with dragon scales, an epiphytic fern botanically known as Pyrrosia piloselloides.

You will have to manually remove the fern from your tree. Engage the services of a landscape company if you cannot reach the higher parts of the tree. 

Any dead parts of the tree that are revealed after the fern’s removal will need to be pruned. If the tree is still in good form after pruning, you will need to work on improving its overall health and vigour, including regular checks for, and removal of, dragon scales. A weak and unhealthy tree will easily be colonised by the fern.

• 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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