Root Awakening: Rose Cactus grown as medicinal plant in S'pore

The raw leaves of the Rose Cactus are used in folk medicine to treat cancer, rheumatism and ulcers.

PHOTO: ALAN TOK

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Rose Cactus grown as a medicinal plant

I have had this plant for almost a year and it flowered recently. The flower opened for a few hours, but closed up by late afternoon. It did not open again and fell off the stem a few days later. Is this normal? Also, are the leaves edible?

Alan Tok

Your plant is known as the Seven Star Needle in Chinese or Rose Cactus in English. Its botanical name is Leuenbergeria bleo. Its flowers are short-lived as described.

This plant is a leafy cactus that is grown for its medicinal properties. Its raw leaves can be eaten in small amounts, and are used in folk medicine to treat cancer, rheumatism and ulcers.

Miniature orchid needs more light

My orchid has flowered twice this year. It grows in a coconut husk and I fertilise it weekly with liquid fertiliser. Roots are sprouting from new shoots.

How do I repot the new shoots? Also, how can I help my plant grow bigger?

Janis Tan

Your miniature Dendrobium appears to be filling its pot. After the flowers have faded, move it to a larger pot. Remove the coconut husk's chunks - they break down and retain too much water, which may cause roots to rot. Instead, pot the plant in coarse charcoal chunks, which will provide an aerated environment for the roots.

Your orchid's new growth is much larger and taller - this is a sign that it is being grown in a shady spot. Grow this orchid in a location which gets filtered sunlight for four to six hours a day. Regular feeding with a water-soluble fertiliser and exposure to light will promote robust growth and frequent flowering.

Kaffir lime may need nutrients, better soil

The leaves of my kaffir lime plant are turning yellow. What can I do?

Goh Boon Leng

The yellowing of your plant's older leaves may be a sign that it lacks nutrients such as nitrogen.

Have you been fertilising your plant regularly? If it has been growing in the same pot for a long time, it may have exhausted the nutrients of its growing medium. The soil could have also become compacted, meaning that the drainage and aeration are poor, which will negatively impact root health and prevent the plant from taking up nutrients. The pH of the soil may no longer be optimal as well.

You may need to move the plant to a larger pot with a fresh, well-draining and friable potting mix. Note that citrus plants do not like waterlogged soils.

Periwinkle plants not edible, banana plants still young

What plant is this? It bears purplish-pink flowers and looks like a periwinkle. Is it edible and what are its growing conditions?

I also have two banana saplings. When will they bear fruit and what stage of growth have they reached?

Sarish Rian Kalai Mahran

The first picture is of a young Madagascar periwinkle (Catharanthus roseus). It is generally regarded as a toxic plant and is not edible, although it has medicinal uses.

Ensure your plant is in a sunny spot with well-draining growing media, as it is not tolerant of waterlogged soil and succumbs easily to disease under such conditions.

Your banana plants are still young. If they have been grown from seeds, they are likely to be a species banana - rather than cultivars grown for their edible fruit - so their fruits will also contain many seeds and be generally unsuitable for consumption.

Depending on the species or cultivar, most banana plants can grow quite large, so the size at which a plant produces fruit will vary.

A single banana plant needs a pot of at least 60cm in diameter and depth to thrive.

Potted plant likely the Longan

What plant is this and how do I care for it? I see two types of leaves - could there be two plants in the pot?

Lin Huifang

Your plants appear to be the Longan (Dimocarpus longan). You may want to move them into a larger pot and place them outdoors in a spot which gets direct sunlight for at least six hours a day, as the Longan is not an indoor plant.

It will be difficult to separate the two plants without damaging their roots. You may want to focus on growing the more vigorous one. Longan will not be able to grow large enough to flower and fruit if they are planted in a small pot as shown in the pictures.

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 Hands-on Workshop: Grow Your Edibles Indoors - Understanding Your Plants And Your Space, Part 1 (Aug 27, 9.30am to 12.30pm, Singapore Botanic Gardens, Centre for Education & Outreach, House 1F). Fees are $50 a participant. Register here
Dr Wong is also hosting two free online talks: How To Set Up A Beautiful Outdoor Edible Garden (Aug 27, 2 to 3pm, register here) and Gardening Q&A for August (Aug 27, 3 to 3.45pm, register here)