Root Awakening: Lime plant lacks nutrients

A plant that lacks nutrients will not be in optimal health and, as a result, will not be productive. PHOTO: MICHELLE JAM

Lime plant lacks nutrients

My calamansi plant is about eight years old and produced an abundance of fruit for the first four years or so. It now flowers only occasionally; a few of the flowers develop into tiny fruit. It is placed in a spot which gets full afternoon sun. The plant is watered twice daily, fertilised with goat manure and has compost added every three months.

Michelle Jam

The leaves of your lime plant appear to be chlorotic, which is a sign of nutrient deficiency. A plant that lacks nutrients will not be in optimal health and, as a result, will not be productive.

Nutrient deficiency can be a result of several factors. Check if the soil is too compacted. In compacted and heavy soils, roots cannot grow and extend, as nutrient absorption will be impeded. Compacted soil will also lead to aeration and drainage issues during wet weather and can affect plant health. You need to incorporate high-quality organic matter into the soil to alleviate the issue.

Also, the soil pH level should be in the slightly acidic range. Nutrient availability is affected by soil pH level as they can become "locked up" or insoluble despite the addition of fertilisers. If the soil is too alkaline, you may need to add sulphur powder to bring down the pH level. If it is too acidic, the pH value can be raised by adding garden lime, which is essentially limestone. These can be bought from nurseries and added in small quantities. Do note that changes in soil pH levels will take time.


Epiphyllum is a cacti genus that produces large, scented blooms

PHOTO: CHIA YANG JIN

What is the name of this plant and what are the best methods of growing it?

Chia Yang Jin

The plant is likely a species of Epiphyllum. There are several species of Epiphyllum that are grown in Singapore. It appears to be either Epiphyllum strictum or Epiphyllum oxypetalum. The two species commonly grown here produce large, scented flowers that bloom at night. People often call it by its Hokkien name, "keng huay".

The plant will eventually grow bigger and require a larger pot to thrive. The growing mix should be well-draining and moisture-retentive as the plant is an epiphytic cactus. It needs at least four hours of direct sunlight a day and will produce flowers once it grows large enough, though not constantly.


Turkey berry fruit is an ingredient in thai green curry

PHOTO: PATRICIA LIM PEK HOON

Someone told me the green fruit from my potted plant is edible and can be used to make curry. What is it?

Patricia Lim Pek Hoon

The plant is commonly known as the Turkey Berry. Its botanical name is Solanum torvum. It grows as a large, prickly shrub and produces round green berries that are harvested and used as an ingredient in Thai green curry. It can be propagated from seeds and stem cuttings.


Wilting in tomato plant may be due to transplanting or disease

PHOTO: AUDREY NG

Why did the leaves of my tomato plant wilt suddenly?

Audrey Ng

Was the tomato plant recently transplanted? During transplanting, the roots of your plant may have been damaged and are unable to take up water. Newly transplanted plants should be left in a slightly shady area to recuperate. New roots are produced over time and the plant can be gradually moved to its final growing spot.

Another reason for wilting could be due to watering patterns. Under- or overwatering can damage the root system. Edible plants such as the tomato should be watered regularly to keep the root zone moist at all times. Generally, plants should not be allowed to dry out totally or grown in soggy soil.

Is your growing mix a new one or was it previously used to grow other plants? Depending on the cultivar, tomato plants are prone to soil-borne diseases, which infect the roots and vascular system in the stems, leading to the plants' inability to take up water, which will eventually kill them.

Infected plants may have discoloured stems. Once infected, it can be difficult to save it. It is best to grow varieties that are resistant to fungal and bacterial wilt diseases.


Leaves of limau purut infected

PHOTO: GRACIE TAN

What is ailing my limau perut plant and how do I treat it? It is grown in the ground in an open area and receives a fair amount of sunlight each day.

Gracie Tan

Your limau purut plant appears to have a fungal disease that affects the leaves. Ensure your plant gets at least six hours of direct sunlight a day with ample air circulation.

Reduce mechanical damage to the plant to limit the areas for infiltration by disease-causing organisms. Infected leaves should be pruned to prevent the spread of the disease. Also, apply preventive fungicides such as copper soap or lime sulphur. Do note that you should spray the chemical on a small part of the plant and check that it is not sensitive to the fungicide before applying it on the rest of the plant.

Always observe the withholding period - the time that needs to elapse after application before the produce can be harvested - and wash produce thoroughly before consumption.

  • 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.
  • Join Dr Wong at two online talks: Edible Rooftop Gardening (Feb 26, 2 to 2.45pm, free admission, register here.) and Gardening Q&A (Feb 26, 3 to 3.45pm, free admission, register here.)

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