Root Awakening

 Indian Spurge Tree and its botanical name is Euphorbia neriifolia
Indian Spurge Tree and its botanical name is Euphorbia neriifoliaPHOTO: GERRY CHNG
ZZ plant (Zamioculcas zamiifolia)
ZZ plant (Zamioculcas zamiifolia) PHOTO: W.L. HOR

Heliconia lacks potassium

The edges of the leaves on my heliconia are yellow (above). I have fed it with chicken manure and NPK fertiliser and I give it compost regularly. The plant is grown under semi-shade and is slow-growing - it has produced only one bloom so far. This cultivar has dark-red pendulous blooms. What is wrong with it?

Charlotte Yung

Your heliconia appears to be lacking in potassium. Symptoms first appear on mature leaves and an inward marginal yellowing of the leaf, followed by marginal necrosis.

Potassium is highly soluble. It is not held well by soil and is leached. Its deficiency frequently happens during the rainy season.

To alleviate the deficiency, ensure that your soil is rich in organic matter, aerated and kept moist at all times. Feed your plant regularly with a fertiliser rich in potassium.

Heliconias need to be healthy before they flower. You need to first ensure that the soil conditions and nutritional needs are fulfilled.

It is a misconception that heliconias grow in the shade. You should grow the plant under direct sunlight with sufficient water in the root zone - many species and cultivars thrive under such conditions.

Indian Spurge Tree needs full sun exposure

Is this plant an Euphorbia milii? I bought it because I needed something more "resistant" to the bad mealy bug infestation on my white jasmine. I was using nonorganic pesticides and neem oil for 11/2 years to no avail. The seller told me this Euphorbia milii is "resistant" to mealy bugs. Is this true? I grow it on my window planter. How do I care for it?

Gerry Chng

The plant is commonly known as Indian Spurge Tree and its botanical name is Euphorbia neriifolia.

Like many Euphorbia species, this one needs a location with well-drained soil and full sun exposure.

The presence of sub-optimal growing conditions, which could be the lack of sunlight, will lead to a weakened plant that is prone to pests and diseases.

It is advisable to select the right plant for the right location.

For pest management, it is necessary to spray pesticide repeatedly several days apart to ensure pests and their young that hatch from the eggs are eradicated.

Neem oil, which is a contact pesticide, needs to be applied on all parts of the plant such as the underside of leaves to be effective.

You will also need to manually or use a strong jet of water to remove the remaining pests hiding in the plant's tight pockets. These areas are hard to reach by spraying pesticide alone.

ZZ plant (Zamioculcas zamiifolia) PHOTO: W.L. HOR

ZZ plant needs more sunlight to thrive

My ZZ plant is usually kept indoors and is taken outdoors on weekends. I have had the plant for a year, but it does not seem to be growing. Its leaves are turning yellow at the tips and curling. How can I help my plant thrive?

W.L. Hor

Your ZZ plant (Zamioculcas zamiifolia) may not be receiving sufficient sunlight for it to grow. Although it is shade-tolerant, it prefers to be exposed to at least four hours of filtered sunlight daily.

When there is insufficient light and the plant is grown in soil that is wet most of the time, its leaves develop a yellow halo. Hence, it is best to move it to a bright window sill or corridor for long-term growing. You can take it indoors briefly for a few days for display - that should not be detrimental to the plant's health.

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A version of this article appeared in the print edition of The Straits Times on May 12, 2018, with the headline 'Root Awakening'. Subscribe