Root Awakening: Rosemary plant infested with lace bugs

Rosemary (left) and Champaca. PHOTOS: ASAD SHIRAZ, THAVA PARAMANATHAN

Rosemary plant infested with lace bugs

I keep getting these sap-sucking tiny insects on my rosemary. They turn the leaves brown and eventually kill my plants. Would neem oil spray work to get rid of them? Is there another organic option I can try?

Asad Shiraz

Your rosemary plant (Salvia rosmarinus) has been infested with lace bugs, a sap-sucking pest that can be found on rosemary and its relatives such as basil. Organic remedies like neem oil are not as effective in eradicating this pest. You can use pyrethrins or matrine, which are derived from botanical sources.

Synthetic derivatives like cypermethrin, commonly available for sale in plant nurseries, are also effective. Follow the instructions on the label and wear protective gear while spraying the plant.

Observe the withholding period - the time that needs to elapse after application before the produce can be harvested - before harvesting the plant for consumption.

If needed, repeat applications to ensure subsequent generations of the pest are eradicated.

Champaca needs direct sunlight to thrive

I bought this plant about 10 months ago. It came with a bud and two flowers, but produced no flowers thereafter. How can I get it to bloom?

Thava Paramanathan

The champaca plant (Magnolia champaca) needs at least six hours a day of direct sunlight daily to thrive and flower. A lack of sunlight will lead to a weak plant with sluggish growth and flower production will be halted.

This plant is capable of growing into a tree, so you may need to move it to a larger pot if its roots have filled the pot. A pot-bound plant will have limited root space, which will affect its growth over time. Fertilise it periodically to keep it healthy.

If you plant it in the ground, ensure that the soil is well drained and does not become waterlogged during the rainy season. Do not plant it too near the boundaries of your property as its branches may grow over walls and intrude on your neighbour's residence.

Christmas poinsettia in poor health

PHOTO: DYLAN HO

I got this plant last year. Its leaves recently started to shrivel. How can I revive it and what is it called?

Dylan Ho

The plant in the picture is the Christmas poinsettia (Euphorbia pulcherrima). From its yellow leaves, it seems to be suffering from nutrient deficiencies. It may be pot-bound, having exhausted nutrients in its growing medium.

You can try to move it to a larger pot with fresh media and add some pelleted fertiliser with a balanced NPK (nitrogen, phosphorus and potassium) ratio. It should be placed in a location which gets filtered sunlight for at least six hours a day.

Note that the plant may remain vegetative - a growth characteristic of foliage production in tropical Singapore - if you have managed to keep it alive. Its bracts may not turn red and flowers may not be produced as the temperatures in Singapore are too high and the days here are not long enough to start the flowering process.

Plant is the variegated Indian borage

PHOTO: JACQUELINE LIM

Is this plant edible?

Jacqueline Lim

The plant in the picture is the variegated version of the Indian borage (Coleus amboinicus). It is often mistaken for the mint plant, though both plants belong to the same plant family, Lamiaceae.

This plant has thick furry leaves with a distinctive scent and can be used as a substitute for oregano. The leaves can be boiled to make a beverage that can soothe the throat and reduce coughing. They can also be coated in batter and fried as vegetable tempura.

Plant is a cultivar of Capsicum chinense

PHOTO: CHEAH CHEW PING

Our condominium gardeners said this is a chilli plant. What chilli is it and how can it be used in cooking?

Cheah Chew Ping

The plant is indeed a type of chilli. It is likely a Capsicum chinense and the cultivar could be Naga Morich, which is often sold in local plant nurseries. It is a very hot chilli that reportedly measures one million SHU on the Scoville scale (a measurement of the spiciness of chilli peppers, recorded in Scoville Heat Units).

Wear gloves when handling this plant if you are using it in cooking. It can be used to make hot sauces. Only tiny amounts are needed to flavour food for those who have lowerspice tolerance.

  • 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.

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