Gardening with Wilson

Most Chinese would be familiar with the edible arrowhead that comes around during the Chinese New Year period early in the calendar year. Some families buy the corms of that particular arrowhead (Sagittaria latifolia) which are then sliced and fried to make arrowhead chips. Some of us grow them in a shallow tub of pebbles and watch them send up upright shoots that end with arrowhead-shaped leaves.

There are a number of ornamental arrowhead species which are grown by aquatic gardeners. There is one that caught my attention but this species is not commonly available in Singapore. It’s supply is sporadic at best. Botanically known as Sagittaria montevidensis, this plant has common names that range from Spongy Arrowhead, Hooded Arrowhead, Long-lobed Arrowhead, Mississippi Arrowhead, Giant Arrowhead and Aztec Arrowhead.

Note that this plant has been reported to be a weed. Sagittaria montevidensis began invading rice fields in southern Brazil in the 1980s. It was discovered at that time, that a herbicide-resistant biotype had developed within the populations found in agricultural areas.

Sometimes stated as a native of the United States or Brazil, Sagittaria montevidensis is one arrowhead species with large showy flowers. Its flowers are borne in whorls or pairs at nodes. Like other Sagittaria species, the flowers each has three petals, each of which is white with a yellow base, and three green sepals. What’s quite different is that there is a large dark red spot at the bottom of each petal.

In my research about this plant, I found out that Sagittaria are monoecious plants. The pistillate (female) flowers are borne low on the inflorescence while staminate (male) flowers produced higher up. The fruit is said to look like a flattened winged achene with a single seed. Female flowers are said to produce numerous seeds which have a high germination rate.

It grows as a marginal aquatic plant, thriving in boggy areas with shallow water. The large, sagitatte leaves of Sagittaria montevidensis are borne on upright spongy petioles (they bruise easily, so handle them with care!) which may reach a length of more than 0.75 m, depending on the growing conditions. Unfortunately, its attractive inflorescences are typically borne lower than the leaves and take on a decumbent growth habit (lying on the sides).

Sagittaria montevidensis is best planted in muck inside a large water-tight container with about 15 cm of water depth. Place this plant in direct sun or semi-shade outdoors. I would prefer the latter situation as the tropical sun can be far too intense.

Most Singaporeans are familiar with the Fragrant Pandan (Pandanus amaryllifolius) which produces fragrant leaves that find numerous uses in our local cuisine. That plant adopts a clumping growth habit and lives happily both in dry land or in water. In the Pandanaceae family, which the Fragrant Pandan belongs to, contains numerous other plants. One of which is Freycinetia cumingiana, which is also commonly called the Climbing Pandan. 

Freycinetia cumingiana is an evergreen climber that feature stems that can grow up to 2 m long. Slender roots grow along the stem which help the plant to attach to a tree, shrub or rock on which it is growing. The slender leaves of Freycinetia cumingiana are dark green and leathery and can grow up to 25 cm long. Each is pleated into an ‘M’ shape and has spines along the margins, similar to those seen in the Fragrant Pandan. For me, a clump of Freycinetia cumingiana looks like a bamboo plant when viewed from a distance.

Besides its interesting growth habit, plant collectors grow this plant also for its ornamental bright red-orange floral bracts. (bracts are modified leaves that on this plant resemble flower petals). Freycinetia cumingiana is native to Tropical Asia, Malesia and Philippines. This species is cultivated on Maui for sale as cut flowers throughout the United States. The Kalanguya tribesmen in the Philippines pound the roots of  this plant for fibers to sew a hunter’s coat.

Going back to the Fragrant Pandan, we know that it has never been recorded to produce flowers. Note that Freycinetia cumingiana is dioecious which means that the male and female flowers are produced on separate plants, although on occasion, the same plant will produce both flower sexes. Male and female flowers are densely produced on white cylindrical spikes housed in the middle of the bracts, while female flowers consist of several ovaries.  Clusters of three or four flower spikes containing either male or female flowers are borne at the terminal ends of branches.

Freycinetia cumingiana is easily propagated from stem-cuttings. For higher rate of success, choose stem tips with roots already developed. These stem sections will root easier.  Freycinetia cumingiana is forest plants so they are best grown under shade in an outdoor garden. Grow this plant in well-draining, slightly acid soil that is kept most at all times.

Commonly known via a range of names such as Purple Shrimp, Blue Shrimp, Rose Pine Cones, Maracas Brazilian Fireworks or simply, Brazilian Fireworks Plant, Porphyrocoma pohliana is a tropical evergreen plant that is a prolific bloomer in the tropics. It is a member of the Acanthaceae, a family consisting of many ornamental flowering shrubs used widely for landscaping in Singapore and similar climates.

I remember seeing this attractive plant being offered for sale in Singapore a while ago, but it has since disappeared once again. Native to South America, Porphyrocoma pohliana grows as a shrub that can attain a height of about 30 cm. It features very ornamental leaves that are deep green which are adonred with silver veins. The plant also produces extremely showy terminal spikes which are covered with long-lasting deep pinkish-red  bracts. The true flowers of Porphyrocoma pohliana are purple in colour and they contrast quite starkly with the overlapping bracts.

One may wonder why this plant is has the ‘fireworks’ word in its common name. In one of my searches on the Internet, the fireworks part was said to have been derived from two sources. One is the appearance of its deep red flower bracts that develop purple flowers, creating an explosion of color. Second, as flowers fade, it can shoot its small black seeds across the surroundings where it grows. Porphyrocoma pohliana is said to be able to self-seed readily and may become a weed in your garden!

Interestingly, it is one of the shrubby Acanthaceae members which can be grown from seeds which are offered for sale by mail order nurseries. Like other Acanthaceae members, it can also be grown from stem-cuttings. It should be grown in a fertile, well draining soil mix that is rich in organic matter. Like many shrubs, it is necessary to prune Porphyrocoma pohliana regularly to ensure that it retains a compact growth habit.

Many Internet resources say that Porphyrocoma pohliana is an indoor plant because it is a shade-loving plant. However, the apartment gardener is to be advised that this plant is not suitable for growing long term inside your apartment. Conditions there are far too dark for the plant to grow. The best area in an apartment for growing Porphyrocoma pohliana is either on the balcony or corridor where it can receive filtered sunshine or bright indirect light for at least 6 hours daily. Outdoors, this plant can be grown in the shade, but not in full or direct sunlight. Strong sunshine can bleach the leaves.

Solanum pseudocapsicum (most commonly known as Jerusalem Cherry) has been a Lunar New Year festive plant  in Singapore. It is a good example of a non-traditional plant that has been turned into a festive plant for the Spring Festival. This plant could have acquired an auspicious meaning via its attractive fruits that come in a range of colours shown over the period of fruit maturation and ripening where they first appear green like jade, then gold and finally, red like a ruby. All parts of this plant is poisonous. Of particular note are its fruits which look like cherry tomatoes (they contain solanocapsine and other alkaloids), so keep fruiting plants and fallen fruit out of reach by young children and pets.

Solanum pseudocapsicum is documented to be a widespread and extremely variable species and this plant can grow as a small erect shrub. In Singapore, we get plants in the nursery that are in the range of 30 to 50 cm tall when they are sold as container plants for display. If left to grow, it is documented that a plant can grow up to 1 m tall, if grown in the ground. Some cultivars can also adopt a prostrating growth habit. Cultivated plants have rather smooth leaves  and produce have large flowers and fruit.

Some years back, only the variety with all green leaves is available for sale in Singapore and this year, we get to see a new cultivar with variegated leaves. Solanum pseudocapsicum is native to the drier areas of Central and South America, from Mexico to southern Brazil, Argentina, and Uruguay, from sea level to 2600 m. Widely cultivated throughout the world, often escaped in tropical and subtropical areas.

With these growing conditions in mind, if one is  to grow Solanum pseudocapsicum in Singapore, we have to ensure plants are grown in moisture-retentive and well-draining soil. Water well and let the soil become moderately dry between waterings. If you noticed leaves falling, it may be a sign that the plant is given too much water and the plant is experiencing wet feet. Fruit drop could be due to insufficient light. It is a sun-lover and hence it is best positioned in a sunny location.

To encourage bushiness, prune the plant regularly or by pinching the growing points. Do also remember to feed your Solanum pseudocapsicum with liquid fertilizer during the active growing stage. Like chillis and tomatoes, you can help to promote fruit set by tapping its flowers to distribute pollen but also make sure the plant is receiving sufficient sunshine and not grown in too windy a place which can be too dry. Similarly, note that Solanum pseudocapsicum is prone to attacks by whiteflies, mealy bugs, aphids and spider mites attack and frequent checks are required to ensure good health of your plant.

To herald the Spring Festival, many Singaporeans flock to local nurseries to buy various festive flowers and plants to decorate their homes. However, many of these plants originate from the temperate climate and do not fare well here. In my contribution to the Straits Times in my official capacity as an NParks staff from the Hort Excellence division, I listed a handful of traditional and new alternative plants that can be used for the same purpose.

The desert rose (Adenium obesum) , tropical pitcher plant (Nepenthes species and cultivars), scarlet star (Guzmania lingulata cultivar) and miniature dendrobium orchid (Dendrobium hybrid) are plants that has been marketed for several years as festive plants for the Lunar New Year. The only new and ‘unconventional’ plant in the list is the nerve or snakeskin plant that is botanically classified in the genus Fittonia. Numerous new cultivars with appealing leaf colours, shapes and sizes are now available and some of those with intensely red leaves are highly suitable for the Lunar New Year due to their auspicious colour. There are a handful of cultivars with yellowish green leaves and red veins.

Read the above scanned newspaper article for more info!

The water hyacinth is perhaps the first floating water plant we learnt about in school and we were also told that they are fast-growing and troublesome weeds in waterways because of their rapid growth and ability to form dense, impenetrable mats of vegetation which hinder navigation and fishing, obstruct irrigation and drainage of farm land and crowd out other plants. As a result of this, this water plant has earned itself a bad name.

But do you know that the water hyacinth is one beautiful water plant? For those of us who have seen it bloom, you will know what I mean. Water hyacinths are members of the Pontederiaceae family which produce spikes of pretty lavender flowers (like the bulbous hyacinths) on top of lush, shiny leaves. There are two species of water hyacinths that one can can choose from.

The first and most common species is Eichhornia crassipes. The leaves of this plant grow from a rosette and the rounded base of each leaf is inflated and spongy which helps to keep the plant afloat on the water surface. For those of us who have picked up one plant a pond, one will observe that the water hyacinth has feathery, freely hanging roots are almost black in colour. These roots do not anchor the plant to any base and hence a water hyacinth is free to float around. Under optimal growing conditions, water hyacinths are prolific bloomers but each flower is rather short-lived, lasting for at most a day or two.

Plants also propagate rather freely by sending out new plants via stolons like a strawberry plant. Although its growth rate can be a nightmare, people have put the water hyacinth to good use after finding out it has phytoremediation properties as it can soak up soluble heavy metal ions and cyanide in polluted waters. The water hyacinth plant also has abundant nitrogen content and it has been harvested and used a substrate for biogas production.

People have also harvested water hyacinths from overgrown colonies for making green manure, compost and mulch for soil improvement. It is sometimes used as a fodder for animals for buffalos and pigs (this is why in Singapore, the older generation calls this plant as the ‘pig plant’ (猪草)). The water hyacinth is also eaten has a leafy vegetable in Taiwan and Java but do exercise caution before consumption as this plant can be contaminated with toxins if it is harvested from polluted waters.

There is another species of water hyacinth known as Eichhornia azurea and its common name include the creeping water hyacinth, peacock water hyacinth. It is less common in Singapore and its flowers are more lavender in colour and smaller compared to Eichhornia crassipes. One will also notice that the yellow spot in the dorsal petal of this species to be more prominent which is not surrounded by a darker patch of purple seen in Eichhornia crassipes. The plant also adopts a slight different growth habit as it grows along a long stem unlike Eichhornia crassipes which adopts a rosette growth habit. Its roots are also less feathered. Eichhornia azurea is propagated via stem-cuttings instead of separation of its stolons (for Eichhornia crassipes). The stems of this species are used to make furniture and baskets.

Both water hyacinth species are sun-lovers and demand a location with more than 6 hours of direct sunshine to grow well. If they are grown in a shady area, one will notice they will simply disintegrate in a matter of a few days.

Water hyacinths are good for ponds which suffer frequently from algae blooms as they help to soak up excess nutrients! Always keep a look out for the growth of your water hyacinth plants in such a situation – promptly remove excess plants before they invade your pond.

If you are afraid they will take over your pond, grow them in a container of water that has some fertiliser added to it. Note the type of fertiliser added as some are harmful to fish if you intend to have fish in the containerised water garden. Fish is recommended as they help to eat up mosquito larvae.

Interestingly, water hyacinths can also be grown in soil. They do well in soggy soils as long as there is water over their crowns!

Known via a range of common names which include devil bean, large yellow rattlebox and wedge-leaved crotalaria, Crotalaria retusa is a highly ornamental plant that you can grow in your garden. A member of the bean family (Fabaceae), it produces bright yellow flowers that are borne on an upright spike which is presented promindantly above a mass of jade green leaves. For ornamental purposes, this plant is best grown in mass in either a flowerbed or as a border plant.

Sometimes found growing as a weed in wastelands, Crotalaria retusa grows as an annual herbaceous shrub that can attain a height of about 1 m. This plant can only be from seeds and the process is an easy one but trying to get some seeds can prove to be difficult. It loves a sunny spot that is also well draining. Being a legume, Crotalaria retusa can fix its own nitrogen from the atmosphere and hence can be grown in nitrogen-poor soils.

Besides being useful as an ornamental plant, Crotalaria retusa has an interesting characteristic that will probably interest kids. The pod-like fruit this plant produces, when mature and dry, becomes a rattlebox that can be shaken and heard. The common name of this plant ‘rattlebox’ is derived from this interesting feature.  The genus name Crotalaria is derived from the Greek word, κροταλον, which refers to the musical percussion instrument castanet. If you are looking for a candidate to grow in your sensory garden, plant Crotalaria retusa in it to confer the sound/audible component.

Like other legumes, Crotalaria retusa can be grown as a green manure, where mature plants can be worked back into the soil to add nitrogen. It is also grown as a source of plant-derived fibre and dye.  Crotalaria retusa is also grown as a medicinal plant. According to Plant Resources of South East Asia (PROSEA), its roots are used against coughing up blood while its leaves are mixed with those of another relative, Crotalaria quinquefolia, and consumed or applied externally against fever, scabies, lung diseases and impetigo. Flowers and leaves are both edible as vegetables due to their low alkaloid content and are purportedly sweet. Seeds are roasted and eaten in Vietnam. Note that this plant is also nematode-resistant and studies have found dried plant parts can be worked into the soil as a soil amendments to deter and reduce root galling by the root-knot nematode, Meloidogyne incognita.

Lastly, note that Crotalaria retusa is a butterfly host plant. According to the Butterfly Circle website, Crotalaria retusa is the food plant for the pea blue butterfly (Lampides boeticus). Unlike other butterfly caterpillars that chew up leaves, the first two instars of the pea blue bore into flower buds of this plant and consume the flower parts contained within. The larger 3rd and final instar caterpillars will move on to eat the developing seeds within seed pods. For more information on the pea blue butterfly, please refer to the webpage below:

http://butterflycircle.blogspot.com/2009_09_12_archive.html

Do your part for the wildlife and environment around us, try to grow this plant without the use of pesticides. In rapidly urbanising Singapore, we are losing loads of our native species of flora and fauna without many of us knowing. Butterflies have an important role in our environment and one of the most obvious role they play is that of a pollinator where they help to transfer pollen that help plants to set seed and ensure the survival of subsequent generations.

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.

I first came across a medicinal plant that is called ‘ulam raja’ when I was doing a research project on plant antioxidants during my Food Science and Technology undergraduate days in the National University of Singapore. Thanks for my Malay friend, Hidayat, he was the one who brought me to Geylang Serai wet market on several Sunday mornings to search for vegetables and plants that are consumed by the local Malay community.  I have not seen it being put up for sale in most other markets. In the local market, bundles of fresh, young and tender tips of this plant are put on sale. They wilt quickly, however, under our hot weather here.

Botanically known as Cosmos caudatus, it is sometimes called ‘wild cosmos’ by locals here but it is mostly refered to via its Malay name, ulam raja, which translates into ‘king vegetable’. Native to tropical America, it was first introduced to Philippines via the Spaniards, according to Plant Resources of South East Asia (PROSEA). The pinnate to pinnatipartite leaves of this plant are consumed as a leafy vegetable, usually in the raw form, but sometimes also cooked and mixed with coconut sauce and chillies. It constitutes as one of the more common raw plant leaves eaten a salad-like form, called ‘ulam’ by the local Malay community as well as those in Indonesia and Malaysia.

For the uninitiated, the leaves of ulam raja tastes raw and somewhat astringent. When crushed, the leaves emit an odour that is reminiscent of mango. It is considered as a medicinal herb which is believed to possess the ability to cleanse the blood and strengthen bones due to its high calcium content. From my research, a preliminary one which was done with my then postgraduate colleague, the dried leaves of this plants contain high amounts of potent antioxidants. The results of our work was published in the following paper:

Shui G, Leong LP, Wong SP. (2005) Rapid screening and characterisation of antioxidants of Cosmos caudatus using liquid chromatography coupled with mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci. 827(1):127-38.

The plant itself can grow quite tall, up to 3 m tall but is an annual or a short-lived perennial herb. It produces dainty, attractive pink flowers when mature. It should not be confused with the yellow- and orange-flowered Cosmos sulphureus as both species are similar vegetatively and have some vernacular names (randa midang in West Java) in common. The latter are more important as ornamental plants that are a common feature during Chinese New Year.

The ulam raja plant was once difficult to find in Singapore. It can sometimes be found naturalised in abandoned kampongs or wastelands. Occasionally, one is able to find a colony being grown by a Malay resident in a community garden. A few years ago, it was almost impossible to buy pots of this plant. Only recently, I discovered World Farm, a Singaporean wholesale nursery stocking some pots of it for sale to the public. I managed to get some young plants that were weeded out from a colleague’s park a couple of months ago.

This plant is rather easy to grow. It thrives in a sunny spot outdoors with well draining, fertile and moist soil. It is a big drinker and demands a constant supply of food. Under optimal conditions, it grows quickly, flowers and sets seeds very readily. Plants self seed easily and can quickly become a weed in a garden. Harvesting of leaves can commence once plants are 6 weeks old and subsequent ones can be done every 3 weeks. Regular harvesting will stimulate the production of useful and edible foliage and helps to delay flowering.

I was given a division of Orchidantha siamensis by a fellow collector a while ago who knew I was interested in plants that are classified in the order Zingiberales. There is only one genus, that is, Orchidantha, in the Lowiaceae family. This genus consists of about five to eight species of plants that grow in the wet understorey of the lowland forest and are native to Southeast Asia and some Pacific Islands.

The genus name is given due to the orchid-like appearance of the flowers produced by these plants. Flowers are usually produced via a subterranean inflorescence and are often hidden away. One of the petals in each flower is enlarged to give a large lip-like structure similar to what is seen in a true orchid. Flowers of one species, Orchidantha inouei of Borneo emits the smell of dung in order to attract small dung beetles as their pollinators! The plant I have freely flowers and thankfully, the smell of its flowers can only be detected when one really goes upclose to them!

I particularly like the Orchidantha as it is perhaps the most shade-tolerant group of plants I have come across so far. Many foliage plants introduced in many houseplant and indoor plant books cannot match it in terms of the ability to grow and thrive in deep shade often encountered in the indoor living environment. It seems to be also able to tolerate dry air rather well too. From this, I reasoned that they also make good candidates for planting in very dim areas in an outdoor garden.

Best grown and appreciated as foliage houseplants that confer a lush tropical feel, Orchidantha species are herbaceous perennial plants with a clumping growth habit. New growth rise from a rhizomatous underground stem. Leaves are lanceoate in shape andhas several pairs of longitudinal veins parallel to the distinct midrib.

I noticed Orchidantha is best grown in a very shaded area as even rays from filtered sunshine can bleach the leaves, giving them a sickly yellow colour. Intense sunshine will burn them. They prefer to be grown in soil that is rich in organic matter, open and kept moist at all times. Avoid growing them in a windy area as constant air movement can dry plants out. Propagation is easy via division of large clumps.

Orchidantha, apparently, have medicinal and folk uses. The scorched leaves of Orchidantha fimbriatum (syn. O. longiflora) are pasted on the back and chest to relieve chest and back pains. Leaves are sometimes used to wrap food in cooking.

At present, Orchidantha is still difficult to find in local nurseries but I believe its usefulness as a foliage plant for growing in very shady areas, once discovered, will greatly call for a demand for plants to be made available to the nursery trade.