Desert rose needs sun to thrive, but do not let it dry out
My plant's leaves have been turning yellow and then brown in some parts before dropping. I water it about once a week or when the soil feels dry. It is placed in a bright balcony that does not get direct sunlight. What should I do?
The desert rose plant (Adenium obesum) is a succulent that thrives and flowers only when grown under direct sunlight.
A desert rose that does not get enough sunlight will flower less, develop lanky growth, turn yellow and die. Try moving the plant to a sunnier spot.
Although it is a drought-tolerant plant, do not let its roots dry out totally. The plant will dry out faster if it is grown under direct sunlight and will need to be watered accordingly. Feel the soil below the surface to gauge the moisture level.
Philodendron infested with spider mites
My plant's leaves have turned yellow. How can I save it?
Danny Phang Fook Ghay
Your plant is a Philodendron and, looking at the small specks on its leaves, probably infested with spider mites. These sap-sucking pests appear as small red dots that move via a protective, water-repellent web structure. They are commonly found on plants that are grown in a low-humidity indoor environment.
The Philodendron is a foliage plant and will fare better when grown under filtered sunlight in a humid environment.
Wipe the pests off both sides of the leaves with a wet cloth. Apply summer oil, which can suffocate the remaining pests, on a regular basis. Mist the plant regularly to wash off pests and dust.
You may need to use a broad-spectrum insecticide such as abamectin if the infestation is severe, but this should be rotated and used sparingly to reduce the likelihood of the pests developing a resistance.
Lemon trees infested with mistletoe
I grew some lemon trees from seeds. Now and then, I see a parasitic plant growing from the young branches. What plant is it and how can I prevent it from attaching itself to my trees?
Your lemon trees are infested with mistletoe, which is a parasitic plant that can grow quite large over time if left alone. You can prune the mistletoe at the point where it is attached to your trees.
Mistletoe seeds are dispersed by bird droppings, so try removing new mistletoe growth manually as it emerges. Alternatively - depending on the size of the plants and garden - grow your trees in a netted enclosure to keep birds away.
Orchid needs water and filtered light
My plant's leaves turned yellow and fell off. Have I over- or underwatered the plant? Do I need to repot it?
The orchid is likely the Aranda Moonlight. It is not an indoor plant, but is best grown under filtered sunlight for at least six hours a day.
As it is an epiphytic orchid, it is best to grow it in coarse charcoal chunks, which provide an anchor for the roots, and promote aeration and water drainage. Avoid planting it in a potting mix for terrestrial plants or sphagnum moss, as these retain too much moisture and may cause the roots to rot. Water your plant daily so it does not dry out. If the plant is underwatered, its leaves will develop wrinkles, turn yellow and die. Once the growing conditions are met, feed it with a water-soluble fertiliser to promote flowering.
Millipedes decompose organic matter
I am making compost and found these creatures in it. They seem to have shells on their bodies, and coil up when disturbed. Will they harm my plants?
Thomas Lee Chee Chee
The creatures are millipedes, which break down organic matter in gardens. They are natural decomposers and, in small numbers, will not harm most plants. Butthey may accidentally consume the roots of young seedlings. To prevent this, grow seedlings in separate, raised trays and transplant them into the ground only when they are large enough.
Use high-quality, mature compost to reduce the likelihood of the millipede population overgrowing in the future, which tends to happen if carbon-rich immature compost is used.
- 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.
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