Monthly Archives: August 2009

Root Awakening (8 Aug 09)

The second instalment of the Root Awakening column was published on Singapore’s National Day eve. Answers were provided to three questions that were sent in by Straits Times Life! readers.

The first question asked about the yellowing in some common species of palms that were grown in containers. Palms grown in pots showing such a symptom may be suffering from nutrient deficiency. To correct it quickly, it is recommended to water plants with a water-soluble fertiliser such as Phostrogen that contains not only the three major elements (nitrogen, phosphorus and potassium), it also contains the much needed macro- and micro-nutrients.

Plants should not be solely be potted up using burnt earth as it is poor in nutrients. A recommended mix should contain some organic matter such as compost which will decompose to release nutreints and help to retain some moisture in the root zone.

The second question asked about the usage of systemic pesticides on edible plants. For such a case, one has to know what is the active ingredient that is used to make the product, find out more about its suitability to be used on edible plants and the withholding period one has to observe. The withholding period refers to the time that must be allowed to elpapse after application of the chemical before the crop can be harvested and eaten.

The last question asked where one can find the cast iron plant in Singapore. The only nursery that I can find this plant all the time for sale is World Farm that is located at 15, Bah Soon Pah Road. It is a slow-growing plant that is best appreciated for its form and foliage as it does not produce flowers in Singapore.

The Garlic Vine

The garlic vine is a woody, flowering climber that is often featured in tropical garden books. A member of the Bignoniaceae family, known via a range of synonymous botanical names but best referred to as Mansoa hymenaea. This flowering vine is native to tropical South America, from Mexico to Brazil. In Costa Rica, it can be found growing from sea level to 900 m in elevation. Interestingly, it is not related to the common edible onion or garlic at all!

In its native habitat, it is said that the garlic vine attaches itself around the trunk of a large tree for support as it climbs skywards to reach for sunlight. The terminal leaflet of this plant is often modified into a tendril that helps the vine to cling onto a support. Because of its large size, it is only practical to grow the garlic vine in outdoor gardens with a trellis. It is a vine with a moderate growth rate and one need not worry that is will become an unruly resident in the garden.

The garlic vine is well known for its leaves that emit a garlicky smell only when crushed. Its blossoms also give off a faint garlic odour but one need not worry about the garden smelling like the kitchen spice when in flower. Because of this characteristic, it is not surprising that the plant can be used as a substitute for garlic in the kitchen. The entire plant such as roots, stems and leaves have medicinal uses and are used to reduce fevers, treat colds, throat, and respiratory troubles.

The plant is a climbing vine that turns woody and heavy over time. Hence it is recommended to grow it on a strong timber trellis in an exposed area where it can receive direct sunshine for most of the day. It is best to grow it in well-drained soil that is mulched at the base with compost to keep the roots cool and moist. Keep it well-watered so that plants do not shed its lower leaves which can make vines look straggly. 

Like many other flowering vines, the garlic vine should not be overly pruned as flower buds appear on new growth. Many gardeners make this mistake by pruning away the vines to keep new growth in check and as a result, plants refuse to produce flowers. Semi-hardwood cuttings can be taken for propagation. Each stem should have at least 3 nodes and can be stuck into a mixture of sand and compost to start the rooting process, after removing some leaves to reduce water loss. Rooting hormone powder is usually not needed.

This vine is not a constant bloomer. It occasionally produces flowers here in Singapore and whenever it decides to do so, the flowering is often described as profuse. The entire vine can be covered with flowers. Flowers are trumpet-shaped and produced in dense clusters. Each starts off purple and changes to a lighter shade of lavender with age and finally fading to white before it turns brown and drops off from the vine. At any one time, one can see three different floral colours on the plant.

Home Concepts Magazine (Aug 09)

 I contributed yet another article to the Garden Treats column in the Singapore Home Concepts magazine. In the Aug 09 issue, the topic of the article was on water plants. For those of us who are blessed with an outdoor garden, one can construct a pond in a sunny spot. For those of us who are apartment dwellers, we can still enjoy a water garden by having a simple, water-tight container to house some fish and grow a couple of small water plants.

I introduced five water plants that can be grown in a water garden. They include species that can be classified as floating, submerged and marginal water plants. A beautiful floating water plant that I introduced was the water hyacinth (Eichhornia crassipes) which is a sun-worshipper. It does best in an area with direct sunshine. Otherwise, a plant can be observed to melt away and that can happen in less than a week.

I introduced a number of marginal water plants which include the pennywort (Hydrocotyle species), water celery (Oenanthe javanica) and star grass (Dichromena colorata syn. Rhynchospora colorata). These are best in soil that is kept moist at all times. They can be grown inside a container or at the edge of a pond and thrive in a sunny to semi-shaded location. Pennywort and water celery are two aquatic plants that have food and medicinal uses.

For the submerged water plant candidate, I featured the infamous marimo ball (Aegagropila linnaei) which is a species of aquatic algae that grows in a spherical mass that are well known to have originated from Lake Akan in Hokkaido, Japan. Because of its temperate origins, this algae (not a true moss) ball is best kept in a jar of water placed in an airconditioned area (< 25 deg C) and hence makes a good plant for the office executive to grow. It is exceptionally slow-growing and one does not have much to do other than to make weekly water changes. One more plus point is that it does not need a lot of light to thrive.

Root Awakening (1 Aug 09)

 The first Root Awakening column for August 09 was published yesterday. As usual, answers to three gardening questions were given.

The first question wanted recommendations for common food plants such as mint and fruit trees like lime and starfruit. Since such plants are edible plants, I thought using contact, less toxic and more environmentally friendly alternatives to synthetic pesticides would be a better idea. White summer oil and neem oil can be used to suffocate small sucking insects at an early stage while the latter is also effective in some instances to deter chewing insect pests. 

The second question asked why the leaves of a iron tree (Dracaena fragrans) are drying up. In general, this popular houseplant would benefit if it is grown in a bright location such as a windowsill, balcony or corridor that has some filtered sunshine for 6 h daily. Dried leaves may indicate an accumulation of fertiliser salts in the soil or moisture stress. For the former case, one is advised to flush the root zone and soil with water to reduce the amount of accumulated fertiliser salts. A plant that is growing in dry soil for long periods may exhibit lower leaves that turn yellow which are eventually shed away. It is recommended to grow this houseplant in soil that is friable and kept moist at all times.

The last question asked why the tips of the inflorescences of an orchid plant grown in a windy area had turned yellow and dry. Developing orchid buds are susceptible to excessive heat and dryness. In an area that is windy and sunny, the developing young flower buds can turn dry and this can be aggravated by the lack of watering. Increase frequency of watering may also help to reduce the likelihood of moisture stress. Apply a mulch of sawdust to reduce the rate of evaporation.

It may be a good idea to grow orchids that are prone to such problems in a cooler and shadier location. Note that not all orchids are shade-lovers. There are orchids that need to be grown in full sunshine to flower.

Additionally, pests such as thrips and spidermites can also cause similar problems on developing flower buds. Hence, it is recommended to apply a preventive spray of white summer oil (for mites) and Confidor (for thrips) when buds are forming. These two pests are problematic in hot and dry areas.