Root Awakening: Lemon plants best grown in outdoor environment

Lemon flowers thrive under direct sunlight

My lemon tree, even after three years of cultivation, has not produced fruit. What should I do?

Ricky Lee Cheng Kee

Lemon is a plant that demands a sunny spot to grow well. It should get at least six hours of direct sunlight and is more suitable for growing in an open outdoor environment. The lack of light, especially in high-rise apartments, may lead to a plant that is largely vegetative.

Chilli needs sufficient light and water to produce fruit, kaffir lime leaves infested by mealy bugs

My chilli plants seem to support the growth of only one fruit at any time. There were a few flowers in one of the pots, but only one bore fruit while the rest fell off. My potted plants were also eaten by caterpillars in the preceding weeks. When I exposed the pots to five to six hours of sunlight daily, the leaves seemed to be lighter green than when the pots were hung over the ledge and the sunrays were partially blocked. I also think they are not getting enough nutrients from the crushed eggshells that I add once a month or so.

What is the white stuff on the reverse side of my kaffir lime leaves and what can I do to protect the plant? Also, are the young leaves naturally a shade lighter than the matured ones? How can I fertilise the plant to boost its growth?

Oh Choon Yean

Chilli plants thrive when they are grown in a sunny spot. Fruit production can be hampered when the plants are not receiving sufficient sunlight and water.

When leaves turn yellow under sunny conditions, it could be due to lack of water, especially if the plant is grown in a pot.

When plants are pot-bound, their roots fill the container and the growing media may not hold sufficient water for the plant’s needs. As such, the plant suffers from stress, and flowers and fruit can be aborted.

Also, a limited soil volume may not have sufficient nutrients required for plant growth, especially if fertilisers have not been added regularly.

You may have to perform hand pollination by using a small paintbrush or an electric toothbrush to help increase the chance of fruit production. There are numerous videos online that you can refer to for more details.

The cotton-like patches on the leaves of the kaffir lime plant may be mealy bugs or scale insects, which are sap-sucking pests. If there are only a few insects, they can be removed easily by washing them off your plant.

Inspect your plants regularly and take action promptly before the pest population becomes too big and detrimental to your plant’s health. Scales and mealy bugs can be managed by spraying your plants with summer oil, which suffocates them. Thorough coverage is essential to provide adequate control.

Orchid seed germination requires specialised equipment

Do you have any recommended resources for germinating and growing orchid seeds in agar-based media?

Samantha Pradeep Rajarathna

Although there are videos and other resources online, orchid seed germination courses are not commonly available. This is because the procedure involves an aseptic technique that requires equipment not readily available to the average hobbyist. The risk of contaminating the plant is also high.

If you need help germinating seeds from a pod, you can seek out commercial orchid nurseries in Singapore as well as Temasek Polytechnic’s Horticulture Services Facility, which provide such services for a fee.

Caterpillar of the oleander hawk-moth eats leaves of oleander plant

I have had this plant for many years. Most of the time, its leaves are eaten by insects. I have managed to catch a caterpillar so far. What can I do to prevent this from happening again?

Richard Lim Lai Huat 

The damage to your oleander plant appears to be caused by the larvae of the oleander hawk-moth. The caterpillars of this moth consume leaves of plants belonging to the frangipani family (Apocynaceae), of which the oleander plant is a member.

Inspect the plant regularly to check for caterpillars and their waste, which appears as black pellets, and signs of eaten leaves. Remove the caterpillars once you see them and give them to enthusiasts to rear. This method requires no pesticides, which is safer for you and the environment.