Monthly Archives: February 2009

The Beautiful Sandpaper Vine

Posted on February 6, 2009 | 1 Comment

Petrea volubilis, also known commonly as the sandpaper vine, Queen’s wreath or purple wreath, is a member of the Verbena family, Verbenaceae. It is a flowering climbing shrub that is grown for its beautiful blue flowers that are borne on pendulous racemes. Blue is a rare flower colour in the tropics and Petrea volubilis is considered by some gardeners as the substitute for the Wisteria in the tropics and subtropics. There is a version that bears white flowers which is rare and difficult to find.

Although this drought-tolerant plant will grow and flower without problems here in lowland Singapore, fellow local gardeners report that it is perhaps more rewarding to grow Petrea volubilis further up north of Malaysia and Thailand where there is a distinct dry season to induce more profuse flowering. The recent prolonged dry and hot spell in Singapore seemed to have triggered flowering in several potted specimens of Petrea volubilis located in NParks’ Pasir Panjang Nursery.

The genus name Petrea is derived from the name of Lord Petre who is a famous plantsman and collector of exotic plants in the 18th century. The specific name volubilis has the meaning of ”twining”, which refers to the climbing habit of this plant. A candidate for growing in an outdoor garden in a location with full sun or semi-shade, Petrea volubilis is usually grown against a strong support. When there is no support, plants will twine around themselves  and form a rounded shrub.

Each flower borne by Petrea volubilis has five, light blue and slender sepals which spread out almost equally like a star. The actual flower resides in the center of each of these star-like sepals. It is smaller but is quite impossible to miss when it opens as each flower is coloured with a more darker blue or purple colour. One will also notice a distinctive white spot on one of the petals.

The sepals are persistent, that is, they stay on the inflorescence for quite some time even after the flowers have faded. They will continue to possess the attractive light blue colour shortly after the flowers dropped off. However, in a rather gradual pace, these sepals will turn greyish as they age and finally become brown and dry before falling off. If the flowers have been pollinated earlier, each of these will bear a fruit capsule which is dispersed by the wind. The sepals take on the role of flight wings which assist in seed dispersal via wind. The sepals spin like a propeller when there is a breeze which help to keep the fruit in mid-air.

One may wonder why Petrea volubilis is called the sandpaper vine. It will only become apparent if one has access to the plant. This particular common name comes from the fact that the leaves of Petrea volubilis is rough to touch. The upperside of each leaf is rather coarse compared to the leaves of plants we usually come across.

It is interesting to note from the profile on Petrea volubilis published on ZipcodeZoo.com which mentioned the innovative uses of the elliptical leaves of this plant as a substitute for sandpaper for small handycraft work and emery board for filing finger or toe nails! They are also used by men who shave the hair off their head as an aid to provide a shiny look!

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Posted in Flowering plants, Tropical ornamentals

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Snakegourds in the Community Garden!

Posted on February 4, 2009 | Leave a comment

Snake gourds are interesting members of the melon family, Cucurbitaceae. Botanically, they are produced by a vine known as Trichosanthes cucumerina var. anguina. The nomenclature of this plant can be quite confusing. As stated in the Plant Resources of South East Asia (PROSEA), cultivated forms have been traditionally distinguished as a species (Trichosanthes anguina L.), subspecies (subsp. anguina (L.) Greb.) or variety (var. anguina (L.) Haines), though it seems more appropriate to classify these in a cultivar group (e.g. cv. group Snake Gourd).

Flowers of the snakegourd are very attractive and can be considered as rather unique in terms of their appearance among the cultivated cucurbits. Similar to those borne by the bottlegourd, the flowers of the snakegourd are white in colour but have fringed edges with fine filaments. They measure up to 3 cm in diameter and are hence large enough to be easily spotted from a distance.

It is interesting to note that although snake gourds have been documented to be night-blooming, the variety I have in my community garden is a day-blooming cultivar. There was one evening that I went down to the garden armed with my camera and was disappointed to find that the flowers have closed shut. I was surprised to discover that there are new flowers in bloom when I went back the following morning.

Like most of the cultivated cucurbits, the snake gourd plant is a monoecious annual vine, bearing separate male flowers and female flowers on the same plant. Male and female flowers are borne between each leaf axil. Interestingly, several male pollen-bearing flowers grow in a bunch whereas the fruit- and seed-bearing female flowers occur singly, as shown in the photograph above. In the photo below, one can see a snakegourd fruit hanging from a leaf axil that was formed after a solidary female flower was pollinated. A bunch of male flowers occurring on the same leaf axil is still in bloom.

Depending on the variety, the slender and serpent-like fruits of the snakegourds can grow up to a length of 150 cm. Immature fruits are light green in colour with stripes which turn bright orange or red when mature. Fruits are harvested and eaten when they are still immature, when they are about 30 to 60 cm long. The flesh is soft but rather bland and are often cooked and favoured with spicy prawn paste (sambal) or curries. The somewhat mucilaginous flesh is similar to that of the luffa but has more a solid consistency. Mature fruits are inedible as they are fibrous and bitter to taste.

To ensure the snake gourd fruit will grow straight, some gardeners actually hang a stone that is actually tied to the blossom end. My community gardeners did not practise that. The free-hanging fruits have been noticed to grow relatively straight while there was one that grew near the a horizontal support in the trellis grid which we observed to have coiled around it like what a real snake would do as shown in the photograph below! How interesting! My community gardeners have actually recieved feedback from visitors to the garden that they got a fright at night when they came by. They have mistakened the fruits of the snakegourd to be real snakes!

Besides the young fruits, the young shoots, tendrils, and leaves of the snakegourd plant are also eaten as greens. Cucurbit leaves emit an odour when bruised and I discovered the leaves of the snakegourd plant actually emit a rather ‘pleasant’ smell that is reminiscent of a type of cheap chicken biscuits that I used to eat when I was a kid.

The snakegourd plant is definitely worthy of planting in a garden. It is best planted outdoors in the ground because of the large size it can grow to. A strong trellis is hence needed. It likes to be grown under sunny conditions but it must be well watered. The recent month-long drought experienced in Singapore has affected fruit set adversely. Plants should also be fertilised weekly to keep up with its growth rate as well as to ensure that high yields are obtained.

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Posted in Vegetables

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DIY Vegetable Gardening & Compost-making

Posted on February 2, 2009 | 5 Comments

In yesterday’s edition of the Sunday Times, a couple of pages were dedicated to a DIY projects feature and I found two articles in one of the pages that were put under a heading entitled ”DIY Gardening”. One was written on “how to make compost” that was contributed by my colleagues in HortPark while another that was submitted by Mr Rengarajan Premkumar from Far East Flora, focussed on “how to plant vegetables”.

The article by Mr Premkumar on planting vegetables recommended one to plant hybrid vegetable seeds because they are usually of a better quality and have improved growth characteristics than normal ones. The article mainly touched on seed raising only and I thought the reason behind it could be probably due to the lack of print space.

Mr Premkumar suggested that seedlings are best raised in a bright area to prevent them from burning under the heat. Brightness of light can be a difficult concept to grasp for novice. Duration of sunshine is another important aspect that was not mentioned. One may get unhealthy, elongated and etiolated growth instead of strong robust seedlings if light intensity and duration are not sufficient.

In general, edible plants must be grown under direct sunshine that last for at least 4 to 6 hours and under such conditions, they are big drinkers and must be watered at least twice a day. They must also be fed regularly to keep up with the plant’s nutrient needs. Depending on the type of fertiliser, they can be given in the diluted version and more often.

Large containers, such as those similar in size as laundry pails are preferred for growing larger growing edible plants, such as lady’s finger and cucumbers. A larger pot can hold more soil which in turn is able to hold more moisture and allow a more extensive root system to be developed. The lack of water at any one point can cause undue stress and cause plants to abort its flowers and fruits.

The composting method that was introduced in the second article by my colleagues working in HortPark was one that uses aerobic conditions. Aerobic composting is normally faster and produces less odour compared to anaerobic composting. Aerobic composting entails the use of a container with holes or gaps on the side that allow air to permeate into the compost heap.

Anaerobic composting, on the other hand, takes place inside a sealed container. Normally, a container is first charged with compostable waste to its brim and then shut tight to allow breakdown to take place. Fermentation then occurs and rather strong odour can be released from the container. The product that result is usually more acidic and wet to touch.

In contrast, aerobic composting usually results in a drier and more pH neutral product. But it requires ’turning’ (mixing) of the compost heap’s contents on a regular basis to introduce air into the mixture. The usage of a container with holes can be problematic because pests such as ants and other critters would be attracted and have access to the heap’s contents.

To prevent pests from being attracted to the compost heap, individuals who are  high-rise apartment dwllers prefer to use a closed container to do composting at home. Their approach is like a hybrid between the two mentioned above. 

My fellow members from the Green Culture Singapore discussion forum used large ceramic jars for this purpose. They covered the mouth of the jar with a lid that seals it shut. After they added fresh kitchen waste into the heap, they turned the heap to introduce air into it, which also helps to mix its contents evenly.

Because kitchen waste is generated and added to the container everyday, this turning procedure is done on a daily basis. Turning is necessary even after the container is filled to its brim to allow air to get into the heap. Depending on the ratio of green and brown waste in the heap and prevailing environmental conditions, usable compost can be ready for use in one month!

It is important to cut up the organic waste into fine bits before adding them to the heap! When cut up, they break down much easily and faster.

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Posted in Newspaper features, Recycling in the Garden, Vegetables

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Andrew’s Article on the Variegated Costus

Posted on February 1, 2009 | Leave a comment

A gardening-related article that was written by Andrew Tan appeared alongside the Root Awakening column yesterday. This time, Andrew touched on a favourite plant group of mine – Costus – or more commonly referred to as the ‘spiral gingers’. 

Spiral gingers are classified in a family of their own, Costaceae. They are related to the true gingers that belong to the Zingiberaceae family, where several of its members are what we are familiar with, one of which, is the cooking ginger. Spiral gingers differ from the true gingers via their lack of aromatic oils in their sap and adopt a strange but attractive spiralling growth habit.

Spiral gingers are perhaps the most adaptable to high-rise apartment growing conditions. Many other gingers are particular with the windy and dry air conditions encountered in the high-rise indoor environment. Spiral gingers with their either waxy or hairy thick leaves seem to be able to grow well.

Many of these spiral gingers can flower when grown in the ground, but I have yet to see them bloom profusely and regularly when grown inside pots in the high-rise environment. To date, I have only one reliable flowering costus that I would like recommend to the high-rise gardener – Costus woodsonii. It is one not very fussy flowering costus that produces dark red flowering cones on a regular basis that look like fat lip sticks.

There are also spiral gingers that are admired for their foliage, such as the one featured by Andrew, Costus arabicus variegata. It is sometimes called C. amazonicus and is not commonly found locally and so far, I saw some on sale in Ang Mo Kio Floral and Landscape, a nursery that is located just next to the Ang Mo Kio Community Library. Another variegated costus relative, Cheilocostus speciosus, also has a variegated version that is very attractive but taller growing. Below is a link to the post I wrote about the latter on this blog:

http://gardeningwithwilson.com/2008/08/11/variegated-cheilocostus-speciosus-in-bloom/

I noticed also that spiral gingers tend to be attacked by mealy bugs, thrips and aphids when they are grown in the high-rise apartment. They are most effectively eradicated using the insecticide called Confidor which is one that is systemic.

Spiral gingers are best grown in a location where they can receive filtered to direct sunshine for at least 4 to 6 hours daily in the high-rise apartment.  Hence if you have a sunny East- or West-facing balcony, the spiral ginger is for you. Outdoors, spiral gingers prefer to be grown in a location that is sheltered from winds where they can also receive filtered sunshine for most of the day. They must be well-watered and prefer to be grown inside a medium that is moisture-retaining, free-draining and rich in organic matter.

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Posted in Flowering plants, Gardening People in Singapore

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