Use medicinal herbs under supervision
Are these plants (pictured) edible and do they have medicinal properties?
Lau Lin Soon
Photo 1 is Rhinacanthus nasutus and is commonly known as the Snake Jasmine. Photo 2 is Persicaria chinensis or the Chinese Knotweed.
Photo 3 is Achyranthes aspera and its common name is Prickly Chaff Flower; and Photo 4 is Talinum paniculatum, commonly known as Jewels of Opar.
These plants are common medicinal herbs. They need a sunny location to thrive and are best grown in fertile, moist and well-drained soil.
These plants are best used with supervision from a certified medical practitioner.
Young fruit of Hyacinth Bean are edible
I grew this plant (pictured) from a seedling. It flowered in a planter box and has bean-like pods.
What is this plant and are the "beans" edible?
The plant appears to be the Hyacinth Bean, which is also known as the Lablab Bean. Its botanical name is Lablab purpureus.
While there are many cultivars, the one you have produces attractive purple fruit. The immature, tender fruit are edible and can be stir-fried or sauteed.
The mature dried beans contain high concentrations of toxins. They must be boiled for prolonged periods, with changes to the water, to make them safe for consumption.
Consider hydroponics method for edible plants
I have grown a basil plant (left) from seeds and have transplanted and propagated the plant twice.
I usually buy my soil from a nursery in Thomson Road, a wet market flower stall and a neighbourhood florist.
How do I know if the soil is pesticide-free and are the basil leaves safe to consume? Also, why does my basil grow upwards instead of sideways?
There is no way to make sure the soil is free from pesticides unless you send it to a laboratory to test for chemicals. Also, there are no effective methods to decontaminate soil.
If you are worried, you may want to use hydroponics to grow your plants. Here, water-soluble fertiliser is added to inert growing media to grow edible plants.
As for your basil, you may want to prune it every now and then.
This will encourage stems to produce side shoots that will lead to a bushier and more compact plant.
Tip: Showy, fragrant blooms from Odontadenia macrantha
Odontadenia macrantha (pictured) is a member of the frangipani family (Apocynaceae). It is a climber that can be used to cover a trellis in an outdoor garden.
This plant produces clusters of large, showy, light orange flowers which are fragrant.
It prefers fertile, moist and well-drained soil to thrive. It can be propagated by air-layering.
Root or stem rot affecting zinnias
Why do my zinnias (pictured) die when flowers sprout? The seeds came from Malang in East Java, Indonesia.
The plants could be affected by root or stem rot, brought about by overly wet soil - excessive watering does not allow roots to dry out. It could also be due to the growing medium, such as heavy clay soil, that drains poorly and retains too much water.
Grow zinnias in full sun. The plants should also be spaced out as crowded plants are prone to disease. Soil should be moist and well-drained.
You may want to grow your plants in a long trough or flower pot with a suitable growing mix, if soil conditions in the ground cannot be easily improved.
•Answers by Dr Wilson Wong, a certified practising horticulturist and founder of Green Culture Singapore (www.greenculturesg.com). He is also an NParks-certified park manager.
•Have a gardening query? E-mail it with clear, high-resolution pictures of at least 1MB, if any, and your full name to email@example.com.