Monthly Archives: January 2010

‘Learn About Perennial Leafy Vegetables’ Guided Tour

Posted on January 11, 2010 | 2 Comments

Last Saturday, my colleagues and I kicked start 2010′s first of a series of guided tours of selected theme gardens in HortPark. This first tour was conducted in HortPark’s ‘Kampong Daze’ or otherwise also known as the ‘Fruit and Vegetable Garden’. The name of this theme garden is self-explanatory and the guided tour served to showcase to visitors a range of perennial leafy vegetables that can be grown in here in Singapore. I was surprised by the turn-out and a rough estimate would put the number of participants to around fifty.

Most of us are familiar with leafy vegetables such as Chinese cabbage, Chinese kale and Chinese spinach. These are common edible leafy greens that need to be re-grown once they have been harvested. Once they reach the right size, these vegetables are usually pulled out from the ground and brought to the cooking pot. But do you know that there is a group of perennial, ‘cut-and-come-again’ leafy vegetable plants? These plants produce leaves that can be harvested over a longer period of time, without the need to quickly re-grow them. Some species of plants have a longer useful lives than others. For example, the horseradish tree will continue to grow and leaves can be harvested continuously whereas the wild cosmos and Indian lettuce plant need to be regrown once they have started to flower or set seed. One can delay flowering by regularly harvesting the leaves and cutting off the flower stalks once they appear.

In this tour, we also shared with our visitors how some of these plants are cooked and tips on how to grow them. I would like to thank all who came to support this guided tour and I hope it was a fruitful trip for all. At the time of writing of this post, we have the following plants growing in HortPark’s ‘Kampong Daze’ theme garden and we will be adding more in the future:

1. Jew’s Mallow (Corchorus olitorius)
2. Water Clover (Marsilea crenata)
3. Wild Pepper (Piper sarmentosum)
4. Ulam Raja or Wild Cosmos (Cosmos caudatus)
5. Green Sessile Joyweed (Alternanthera sessilis)
6. Ceylon Spinach (Basella alba)
7. Roselle (Hibiscus sabdariffa)
8. Waterleaf (Talinum triangulare)
9. Okinawan Spinach (Gynura bicolor)
10. Scrambling Gynura (Gynura procumbens)
11. Sawtooth Coriander (Ergynium foetidum)
12. Indian Lettuce (Lactuca indica)
13. False Roselle (Hibiscus acetosella)
14. White Mugwort (Artemisia lactiflora)
15. Sweet Leaf (Sauropus androgynous)
16. Rice Paddy Herb (Limnophila aromatica)
17. Water Celery (Oenanthe javanica)
18. Water Sensitive Plant (Neptunia oleracea)
19. Cassava (Manihot esculenta)
20. Spot Flower (Spilanthes paniculata)
21. Horseradish Tree (Moringa oleifera)
22. Chinese Chives (Allium tuberosum)
23. Water Spinach (Ipomoea aquatica)
24. Lasia (Lasia spinosa)
25. Sweet Potato (Ipomoea batatas)

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Root Awakening (9 Jan 2010)

Posted on January 9, 2010 | Leave a comment

The first instalment of the Root Awakening column for 2010 was published today.

The first question dealt with white insects on kangkong plants and this could be an infestation of white flies. To eradicate these pests, spray plants using white summer oil or neem oil. Make sure you cover every part of the plant thoroughly, including the leaf undersides as well as any spaces between leaves. There is also a need to repeat application of the pesticide several times to ensure all progeny that hatch from eggs laid earlier are also eradicated. Check surrounding plants for any signs of infestations as well. Pests from these plants can migrate over at times. They should be sprayed as well if there is any signs of infestation. Alternatively, this could be a fungal disease called white spot that commonly occur in kangkong plant. Note that the spots are not mobile and cause the upperside of leaves to have yellow spots.

The second question was about the growing of the rangoon creeper in a container. Note that the Rangoon creeper is a big vine and it may not be a good idea to constrain it in a pot as it will be likely to suffer from water stress. A plant that has grown larger with a dense crown of foliage tend to have a higher demand for water as it transpires more. The amount of water that can be retained by the soil in a pot may not be sufficient for the plant’s needs. A plant that has been allowed to dry out may show yellowing leaves or shed its lower leaves. It is hence necessary to transplant your vine into a larger pot. One may want to transplant your plant into ground if it has grown too big. For plants grown inside a small pot, do increase the frequency of watering and apply a layer of compost on top of the soil surface to act as a mulch, which can help to retain water and reduce rate of evaporation.

The last question was about the growing of orchids. It is definitely not true that orchids do not require fertiliser. In fact, many species and hybrids need to be feed to grow healthily and produce flowers. Some fertilisers that are good for orchids include Gaviota (available from Far East Flora).

This orchid is an epiphyte and it is likely to be grown in a porous mixture such as  charcoal chips and this dries out quite quickly. Depending on the growing conditions, it may be necessary to water it at least twice daily, especially it is grown under direct sunshine. The problem described by the reader seemed to suggest that his/her orchid plant may be suffering from heat and moisture stress. One can consider adding a little sphagnum moss around the root zone to help retain some moisture. It may be necessary to increase the frequency of watering too. Do also try to relocate the plant to a less windy area or provide some protection by putting up a barrier to wind by growing them amongst some plants.

Do check out the book published by the Orchid Society of South East Asia entitled ‘Orchid Growing in the Tropics’ for more information on how to grow various orchids in Singapore.

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Posted in Root Awakening in ST Life!

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A Sensitive Plant that Swims!

Posted on January 7, 2010 | 3 Comments

Neptunia oleracea is the aquatic equivalent of the common sensitive plant (Mimosa pudica). Commonly known as the water sensitive plant, it grows via long stems and sports the same pinnate leaves like its terrestrial counterpart, which closes up when disturbed.

Unlike the common sensitive plant, Neptunia oleracea does not have thorns and produces flowers that are yellow in colour rather than pink. Interestingly, the mature stems of Neptunia oleracea that are in contact with water develop somewhat differently as they will have a layer of white spongy tissue around the stems formed between the leaves to help them float on water.

Because of these characteristics, I find this plant an ideal and interesting candidate to show as an example to children of a plant that moves, much like the common ones that we now know that include the common mimosa, the dancing plant (Desmodium gyrans) and Venus fly trap (Dionaea muscipula). Without thorns, Neptunia oleracea is safe to handle by children and what’s more, its a mimosa that wears a float to swim in water! It is an edible plant too and children can cook it as a fun activity!

According to Plant Resources of South East Asia (PROSEA), Neptunia oleracea is widely distributed in the tropics of both hemispheres but the origin of the species is uncertain. It occurs wild and cultivated as a vegetable throughout South-East Asia, particularly in Thailand and Indochina.  Neptunia oleracea can be found growing in inundated ricefields and in other fresh water bodies and sometimes becomes a weed which choke up waterways in some countries. A member of the bean family, Fabaceae, this plant has nitrifying capability and releases nitrogen into the water.

In Singapore, this plant is not easily found, perhaps due to the fact that our country has been urbanised to a great big extent and all our waterways have been cleared and paved with concrete over the past few decades of rapid development. It cannot be purchased from local nurseries as well. I managed to find some on sale in a Thai supermarket in Golden Mile Complex, which is known here as the ‘Little Thailand’. Stems of this plant of about 30 cm are sold in bundles. It is best to buy them when they first arrive before they dehydrate over time.

The fresh stems of this plant can be used for propagation. After several tries, I succeeded in propagating Neptunia oleracea and what I did was to simply throw the stems into a pond. The stems rooted rather quickly and the plant started to extend its stems in just a week in water! Plants are best grown inside a pond that is exposed to full sun or semi-shade. Now I have some being grown in the natural pond located nearby HortPark’s Kampong Daze theme garden.

Do you know that the roots of this plant are used medicinally? The people of Kelantan, Malaysia) use the root as an external remedy for necrosis of the bones of the nose and hard palate. The juice of the stem is squeezed into the ear to cure earache and the root is used in the advanced stage of syphilis in Malaysia. An infusion of its roots is rubbed all over the body with rice flour to reduce fever. A common ingredient of Thai cuisine, the leaves and young shoots are said to have a nutty cabbage-like flavour and can be eaten raw (such as after being dipped in sambal blachan) or cooked (added to soups).

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Appreciate the beauty of Alstonias

Posted on January 5, 2010 | 3 Comments

Anyone living in Singapore who visited our local parks and gardens or drives along the expressways would have noticed the gregarious flowering of two species of trees lately. The trees in flower belong to the genus Alstonia and there are two species widely planted in Singapore.  I managed to capture some pictures of one of the flowering A. scholaris that was flowering in HortPark before I left home from work.

They include A. scholaris and A. angustiloba. Both species are native to this part of the world and are members of the frangipani family, Apocynaceae (and expectedly, they exude a white milky sap when any part of the plant is injured). The fruits of Alstonia occur as a pair of long, narrow cylindrical pods that are joined at the base. Seeds are small and flat. Alstonia scholaris is commonly known as the Common Pulai while A. angustiloba is known as Indian Pulai.

In the latest edition of Trees of our Garden City edited by Mr Tee Swee Ping, Alstonias are described to be tall trees that can grow up to 25 m tall and feature a large, pagoda-shaped crown with distinct tiered branching. The leaves of Alstonia are borne in whorls of up to 8 leaves. Each leaflet is oval-shaped. The two common species can be distinguished via their leaf and fruit sizes. The leaves and fruits of A. angustiloba are slightly larger.

The colour of their flowers varies also. The flowers of Alstonia are produced in clusters of 3 to 8 and each flower is rather small. Alstonia angustiloba’s flowers are white in colour whereas those of A. scholaris are greenish yellow . They are both heavily scented and flowering is triggered by a marked dry season. 2009′s December, I find, is unusually dry in Singapore.

Besides being valued as handsome trees that profusely produce scented flowers, Alstonia has various other uses. The sap, which contain alkaloids, exuded from the bark of Alstonia has medicinal properties. The rather light timber from Alstonia is used to make a range of products, from posts, coffins, corks, household utensils, floats to boards. In particular, timber from A. scholaris is used in the past to make writing slates for schools, which gave rise to the species name scholaris.

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The Balsam in the Water

Posted on January 3, 2010 | Leave a comment

Waterlogged areas can be a headache for many gardeners as they can be expensive to improve for growing plants that demand a well-draining location. Ever since I joined the National Parks Board (NParks) and got stationed in HortPark (the gardening hub of Singapore), I got to face the challenges of having to plant up waterlogged areas. One of the plants I got acquainted with was Hydrocera trifolia, commonly known as the water balsam or marsh henna. My colleagues from the Hort Management section planted a grove of Hydrocera trifolia in a waterlogged area near the prototype glasshouses located near the back of HortPark.

Hydrocera trifolia is native to lowland areas stretching from Southern India, Sri Lanka, southern China, Indo-China, Thailand, Peninsular Malaysia to Indonesia and is found growing in ditches, pools, rice fields and marshy places. From its ability to grow in stagnant water and the picture of its flowers shown above, it is clear why Hydrocera trifolia is called a water balsam. According to a Kew Bulletin paper by Grey-Wilson, this plant can grow in water with its stems submerged in water to a depth of 70 cm! For those of us who are familiar with the common garden balsam, Impatiens balsamina, it is a plant that loves to grow in moist areas but never waterlogged!

This plant is a perennial and can grow up to 1 m in the tropics. The part that grows above water is leafy and unbranched and its stems are held erect. Interestingly, the submerged portion do not have leaves and will thicken and become spongy, which I think is an effort by the plant to prevent itself from sinking! How interesting!

However,  Hydrocera trifolia and Impatiens balsamina differ in two ways, in terms of the structures of their flowers and fruits, according to Grey-Wilson. In a Hydrocera trifolia flower, one will be able to observe that there are five sepals and petals, where the latter are all free from one another. In  Impatiens balsamina, the flower usually have 3 sepals and the four petals instead come in two pairs, with the dorsal petal free.

The fruits of Hydrocera trifolia do not split open like those found in Impatiens balsamina which we learn from primary school textbooks that they burst open when ripe to disperse seeds via explosive action. Each fruit of Hydrocera trifolia contain about 5 seeds whereas one can find many more in Impatiens balsamina.

Like Impatiens balsamina, the flowers of Hydrocera trifolia yield a dye and the flowers of the latter are used to prepare a red dye for fingernails which serves as a substitute for henna (Lawsonia inermis). This use is behind Hydrocera trifolia’s alternative common name, water henna.

This plant is easy to grow that are suited for growing inside or near the edge of ponds. Although aquatic in growth habit, one can also grow it in a pot of soil that is kept moist at all times. It thrives in semi-shaded areas to locations with full sunshine and can be propagated easily via stem-cuttings or via layering.

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A Pretty Mint to Grow – Pineapple Mint

Posted on January 1, 2010 | 1 Comment

For a long time, I wasn’t too interested in culinary herbs like mint. However, via a fellow gardening friend from Green Culture Singapore, my perspective about mint took a dramatic turn and I got hooked to the range of mint cultivars that exist. This is perhaps the first time I am ‘declaring’ my love for this group of edible and very aromatic group of plants.

One of the favourite mints is the pineapple mint. Commonly known via the botanical name Mentha suaveolens ‘Variegata’, pineapple mint features very attractive, oval leaves that are variegated. According to the wonderful book ‘The Encyclopedia of Herbs’ by Tucker and Debaggio, this pretty mint should be botanically named as Mentha suaveolens var. suaveolens.

I got this mint via raising stem-cuttings obtained from material purchased from the supermarket. Fresh stem-cuttings root easily in water. Although called the pineapple mint, the leaves of this mint, when rubbed, do not emit a smell similar in any way to the fruit it was named after. In my opinion, its scent is somewhat sweet and fruity compared to the sharp menthol odour expected from a typical mint plant and this property makes this mint more acceptable to those of us who find the usual mint too strong for the senses. 

The soft, furry and wrinkled leaves of this particular mint cultivar are edged with white or cream which makes it a great garnishing material for desserts and ice-cream. Like most variegated plants, the variegation seen on its leaves depends very much on the light conditions it is grown under. Pineapple mint must not be grown under full sunshine in the tropics as an entire day’s worth of exposure to intense sun’s rays has been observed to burn the leaves. It thrives better if given filtered sunshine for half a day. Sufficient light exposure is still essential to reduce the likelihood of etiolation of stems.

Compared to other mints, the pineapple mint is not one of the easier plants to grow. Besides the light factor, its grower has to know that it is not really suitable for growing outdoors without protection from rain. Rainfall in the tropics can be very heavy and all it takes is one very heavy downpour to flatten a colony of this rather fragile mint. Because of its variegation, the pineapple mint is considerably less vigorous compared to other all green mint cultivars.  Under good light, the stems of this mint can become quite thick and grows upright. Under dimmer conditions, it is seen to take on a sprawling growth habit.

I prune it often to keep the growth of the plant compact and neat. Grow it in well draining soil that is rich in organic matter and kept moist at all times. Remember to feed it often to promote robust growth. Lastly, never allow a mint to dry out!

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