Sunday, December 07, 2008

Growing curcumas in the humid tropics

There are many species, and in Thailand, many beautiful hybrids have been developed. The plants will grow and flower well in Malaysia and Singapore. After that they go dormant. Perhaps new plants will emerge and flower one more time but that will be the last of it. I have tried various ways of storing the corms after flowering and found that, for the variety I have been growing, the resting period is 5 months. If If I leave them in the ground, they will rest 5 months and if I store them dry in a basket, and replant them at say 3 months, they will remain dormant for another 2 months in the ground. I have tried storing them in my refrigerator. It makes no difference. The domant period is still 5 months. Better to store in a basket away from sun and rain. If left in the ground they may simply rot away.

After planting, it will take another month before new leaves appear above ground. After that, development will be fast. The soil should be friable, well-drained, and fertile. If you do it right, each of your original corms will flower once and produce two to three side shoots but the side shoots will not flower. When the last of the flowers have faded, dig up the plant and wash away the soil. You will have two or three side corms beside the old one, each of which will give you a new flowering plant in the next round. It appears that each corm needs to be rested before it can flower.

Friday, November 28, 2008

A Borneo origin for the Chinese flowering cabbage Choi Sum (Brassica rapa var. parachinensis)

The origin of the Chinese flowering cabbage ('Choi Sum' in Cantonese)has been a bit of a mystery. It was long popular in China and Japan before it became known to the western world. Most authorities think it originated in Southeast Asia. It certainly grows well in the tropics where it is widely cultivated by ethnic Chinese farmers, but I have never seen it wild in the Malay Peninsula, and the seeds are usually imported (from China or Thailand?). The plant also does not 'escape' and grow by itself without human help. These observations made me doubt the theory of its Southeast Asian origin.

However I recently noticed a small form of this vegetable in native markets in Kuching. It is less than half the size of the form grown by Chinese farmers. I made enquiries and found that it is known as 'sawi dayak'. It is grown by broadcasting the seeds on newly burnt hill slopes on which the inland communities grow hill rice. The very small seeds are sold cheaply in small packets, each containing hundreds if not thousands of seeds, so the plants must be prolific seeders and perfectly adapted to the local environment. Hence I now believe that sawi dayak is the parental wild type of Choi Sum and its origin is indeed Southeast Asia, specifically Sarawak in Borneo.

The Chinese form of this vegetable needs daily watering and tending. The sawi dayak is watered by rain only. It is just the vegetable for the 'let-it-grow-naturally' organic farmer.

Tuesday, September 30, 2008

Physalis alkekengi (Chinese Lantern Plant) has very sweet fruits

I have just spent a week in Inner Mongolia province of China. As usual, I kept a lookout for interesting plants, but the plant diversity in Inner Mongolia is very low compared to Sichuan and Yunnan.

The most interesting find was the fruit of Physalis in a market stall. I think this must be Physalis alkekengi, the Chinese Lantern Plant. The fruit is an orange berry half the size of a cherry but completely covered by 5 expanded calyx lobes. There is a related weedy species in Malaysia, Physalis minima, locally known as letup-letup. Another species, Physalis peruviana, also known as the Cape Gooseberry, was introduced to Malaysia about ten years ago and is sometimes used in restaurants to decorate meat dishes. The fruits of all three species look very similar.

The fruits of P. minima and P. peruviana are both rather tasteless, but the fruits I found in China are as sweet as the sweetest grapes. It is also said to be a highly ornamental plant, with the calyces red in colour when fresh. P. alkekengi is perennial, surviving tbe cold winter by virtue of a resting underground stem. It may not thrive in the tropics. It would be interesting to hybridise it with P. minima to produce a sweet-fruited plant for the tropics.

Wednesday, September 03, 2008

The homing ability of a caterpillar

As a gardener, I love butterflies but detest caterpillars. Whenever I see them on my plants, I flick them off and that is the last I see of them. This is an account of a caterpillar that I flicked off three times and each time, it found its way back to the host plant.

It was a large caterpillar about 7 cm long, black in colour, with a pattern of gold ringed ‘eyes’ and white transverse bands made up of small closely spaced white spots). At the tail end, sticking up, was a spur. This was identified by an entomologist as the caterpillar of a hawkmoth.

I found two of these caterpillars feeding on a plant of Impatiens walleriana (busy lizzie) growing in mixture with other flowering plants on a raised flower bed in my garden. The bed is one brick high and is demarcated by a line of bricks. I flicked the caterpillars off with a stick and they landed about 30 cm away on the lawn . On the next day, one of them was back on the plant. The other was not seen again. At first I thought this was a caterpillar that I might have overlooked. I flicked this off and made sure there were no other caterpillars on the plant. An hour later, I noticed it was back on the plant.

Intriqued, I flicked it off for the third time and this time I watched as it recovered from the shock and crawled on the grass in the direction of the host plant. When it arrived at the dividing brick wall. It tried to climb the wall but gave up. Instead it crawled on the grass alongside the brick away from the host plant until it came to a gap between two bricks that was filled with soil and small weeds. It crawled up this gap to the top of the bed and headed straight for the host plant, past a number of other plants of other species. I was surprised by its ability to make a detour and still find its target.

I was going to give the caterpillar a rest before putting it though some further tests, but when I came back a few hours later, it had disappeared.

Can anyone put me in touch with other accounts of homing ability in caterpillars?

Sunday, August 03, 2008

Acacia mangium growth in relation to light and nutrients

In a recent experiment, we grew Acacia mangium under five light intensities: 4, 7, 25, 50 and 100% side by side with four other rainforest species under conditions free of water stress. Acacia mangium outgrew all the other species as expected, not only under 100% light but also under 50% and 25%. It had the highest leaf turnover rate due to its short leaf life span, which is about 300 days at 4% light dropping to 100 days at 100% light. Its leaf life span drops at a rate of 40 days for each doubling of light intensity. Compared to the next fastest growing species, Shorea roxburghii, Acacia mangium grows 4 times as fast but takes up 15 times as much N, 10 times as much P and 16 times as much K.

Our paper has been published in the Journal of Tropical Forest Science 20 (3) 218-234 (2008). P.S. Tong and F.S.P. Ng: Effect of light intensity on growth, leaf production, leaf lifespan and leaf nutrient budgets of Acacia mangium, Cinnamomum iners, Dyera costulata, Eusideroxylon zwageri and Shorea roxburghii.

Friday, August 01, 2008

Leaf demography, phenology and light

In the humid tropics there is no obvious climatic stimulus to make a tree shed its leaves, but leaf-shedding occurs nevertheless. Some trees shed old leaves and produce new ones all through the year, good examples being the papaya, the oil palm and the coconut. The majority shed leaves all at one go and replace them simultaneously with new leaves. The switchover is usually so smooth that the trees never appear to be bare, so tropical humid forests appear evergreen. In most years there is little or no synchronization between trees, but once in a long while there is a baffling mass synchronization event.

In the 1930s, R.E. Holttum, then Director of the Botanic Gardens Singapore, had the idea that leaves have an inherent life span and are shed when their time is up. He monitored the leaf change cycles in many trees for 10 years or more and found that each species follows an approximate periodicity, with a variation of up to a couple of months. He could not explain the variation.

Recent studies have shown that leaves exposed to full sun have shorter life spans than leaves in shade. A just-published paper by Ms Tong Pei Sin (my student) and myself describes an experiment comparing 5 species (Acacia mangium, Shorea roxburghii, Dyera costulata, Eusideroxylon zwageri and Cinnamomum iners) under 5 light intensities (4, 7, 25, 50 and 100%). This study shows that leaf life span is shortened by a constant amount for every doubling of light intensity. For example, Acacia mangium leaves have a life span of about 300 days at 4% dropping to about 100 days at 100% losing about 40 days per doubling of light intensity. Shorea roxburghii leaves have a life span of about 550 days at 4% dropping to about 200 days at 100%, losing about 70 days for each doubling of light intensity.

Hence leaves do have a life span, but it is a service life span, not a calendar life span. We propose photosenescence of leaves as one of the drivers of phenology in the humid tropics.

Trees in nature, being subject to varying cloud cover, would vary in periodicity of leaf fall because no two periods would ever experience exactly the same combination of cloud cover conditions. A long period of cloudy weather would prolong the leaf life span of many trees and if this is followed by clear sunny days, many trees would trip over their tresholds and shed leaves simultaneously. This would be accompanied by production of new leaves and inflorescences in mass synchrony. The full paper is availble:


Monday, July 21, 2008

Creating cannas for the ever-flowering tropical garden

The creation of new flowers is something most gardeners leave to professional plant breeders. Since there are very few professional plant breeders in the humid tropics, the rate of development of new varieties in the humid tropics is very slow. I would like to change this by getting more gardeners into plant breeding, starting with something really easy -- tropical cannas.

Cannas are good subjects because they come in many different floral colours including red, yellow, orange, pink, cream, near-white and mixed or mottled. The leaves are green, red, or striped. There are talls, mediums and dwarfs. Each flower lasts usually two days but a head of flowers may carry up to 20 flowers. An inflorescence usually bears 2-3 heads of flowers in succession and some bear up to 15heads. For every shoot in flower, another should be half-way and a third pushing up from the rhizome underground. Flowering can be prolonged for years.

Here are some other statistics.
Time from pollination to seed-ripening: about 20 days
Time for treated seeds to germinate: about 7 days
Time from germination to flowering: about 3 months
Time for doubling of plants by division of rhizomes: any time after 4th month

There are few plants that one can hybridize and evaluate within 6 months. This is a phenomenally rapid rate compared to tulips, curcumas and orchids.

As far as I know, all cannas, if fertile, will hybridize with each other. However, many garden forms are sterile. The fertile ones advertise themselves by producing fruits spontaneously and spradically. To start your breeding programme, make a collection of fertile varieties first.

To produce new hybrids, apply pollen from a fertile plant to the stigma of another fertile plant. This is best done in the afternoon, using freshly shed pollen.

Open a fully developed bud (tomorrow's flower). Strip off the sepals and petals until you are left with the two innermost members. One will be a stamen, somewhat like a small petal in appearance, which bears an anther on one side. The other will be a flattened pistil, at the tip of which is the stigma. The anther will already have split and deposited its pollen on to the side of the pistil. The pistil, with the pollen on its side, can then be used to dab the freshly shed pollen on to the stigmas of already opened flowers.

After about 20 days the seed will ripen. The seeds harden on drying and will keep for a year or more. To germinate, make a small cut in the hard seed coat with a wire cutter and plant about 1 cm deep in soil.

Sunday, July 20, 2008

Springtime all the time--the ever-flowering garden

I gave a talk on this topic in Kuching a couple of days ago, and this is a brief summary.

The everflowering garden can only be created where it is warm and moist all the time, as in the humid tropics. The British had a go at it when they ruled what is now Malaysia and Singapore, but most of the flowering plants they used were annuals imported as seeds from Britain. In front of their bungalows, the British created lawns fringed by borders of flowering plants. The lawn tradition survives but the flowering border could not be sustained. By default, gardens in the humid tropics are evergreen--monotonously so! However, in the past 50 years, more and more tropical perennial ever-flowering plants have come into existence. I counted over 100species in my book Tropical Horticulture and Gardening. The ever-flowering garden is now well within reach and should be one of the aims of tropical gardening.

50 years ago, it was a problem to keep bougainvilleas in flower. Now there are ever-flowering bougainvilleas in a wide range of colours, thanks of plant breeding and selection. Other plants that have become ever-flowering are the drunken sailor Quisqualis indica and Kock's bauhinia Bauhinia kockiana. New forms of Hibiscus, all ever-flowering, have been bred in Hawaii and Australia. Ever-flowering heliconias have become common. Ever-flowering Canna were bred by the late Professor Holttum in Singapore but most of these have been lost; we have to start all over again.

I am particularly keen on cannas because they are easy to breed and select. I distributed hybrid seeds in Kuching and encouraged my audience to form an informal club for future breeding and dissemination of seeds. The breeding and selection of cannas will be my next blog.

Tuesday, May 06, 2008

A Natural History Museum in Malaysia

Natural history museums are organizations set up for research on animals, plants, and often of minerals, for the preservation of scientific reference specimens, and for public education through authoritative science-based exhibitions. Malaysia, though one of the top countries in biological diversity, does not yet have a natural history museum. Today a further step was taken to establish one, to be called the Natural History Museum Malaysia (NHM Malaysia).

Nine months ago, the Ministry for Natural Resources and Environment, with financial support from UNDP, appointed a team of consultants to prepare a framework proposal for such a museum. As leader of the team, I presented our report to the Steering Committee for the Museum today. Our report has been accepted, and a small project management team has been set up. The team will be based at the Forest Research Institute Malaysia and will be headed by Dr L.G. Saw.

This will be good news for the scientific community in Malaysia which has been lobbying for a natural history museum for over 20 years.

Sunday, April 27, 2008

Bumper durian crop expected July 2008

There are usually two durian crops a year in Peninsular Malayia, in about December and about July. However, last December the crop was very poor. Last night I came across a few durians for sale. I stopped to talk to the stall keeper. He told me his fruits are the last of a miserable crop that he had obtained from Johore. However, he said there will be a bumper harvest in July, because durians all over Peninsular Malaysia are now heavy with little fruits.

Durians take 3-4 months from flowering to fruiting, so the flowering must have occured in end March to early April 2008. A big flowering event in durians usually coincides with a 'gregarious flowering' event in the forests affecting all kinds of trees. Hence I expect a bumper crop of all kinds of forest fruits, and a feast for the animals of the forest in July to August. It has been many years since the last such event.

A bumper crop is not good news for durian farmers, because it means the price will be too low for them to make a profit, or even to pay for the fertilizers and for the labour to pick up the fruits.

Cooked cabbage as snail bait in a water lily pond

The water lily pond in which I grow Victoria lilies (Victoria amazonica)was suddenly invaded by water snails two weeks ago. Although the undersides of the lily leaves are thorny, the thorns give no protection against snails. A friend who was with me recommended using boiled cabbage leaves to trap the snails. We did this, placing lightly cooked leaves on the water every evening. It works. Every morning, there are dozens of snails on each leaf, which our workers remove and destroy. I do not know if we can completely eliminate the snails by repeated trapping, but the Victoria lilies have recovered.

Monday, April 21, 2008

The golden chain, Lophanthera lactescens

One of the most attractive trees introduced to Malaysia in recent years is the golden chain tree, Lophanthera lactescens. This caught the attention of Dr Mahathir, then Prime Minister of Malaysia, during his official visit to Brazil. Shortly after Dr Mahathir's return, I was asked to identify a sample of the plant at the Forest Research Institute Malaysia in Kepong. Within a couple of years, the first plants were being offered for sale, but they were few and expensive and apparently propagated by cuttings or marcots. The trees were able to flower prolifically, but the fruits were all devoid of seeds.

Last month I was greatly surprised to find trees producing apparently viable seeds. I collected and planted the seeds and after one month, they began to germinate.

Plants raised from seeds are genetically variable, while plants propagated by cuttings are genetically uniform. Genetic variation allows for selection of plants best suited for particular needs, in this case, horticultural needs under Malaysian conditions. The original plants would have been adapted to Brazilian conditions and may be suboptimal for Malaysia. We do not know what could be better because we have no basis for comparison and selection. The successful production of seeds opens up the horticultural possibilities.

I can provide seeds to those in Malaysia or Singapore who would like to try them out.

Friday, April 18, 2008

Alternanthera sessilis to treat high blood pressure

On Aug 1, 2007, I posted a blog on Alternanthera sessilis as a treatment for high blood pressure. A few weeks ago a friend asked me for it and I went to the wet market in Kepong to see if it was available. Not only was it available, but several vegetable stalls were selling it, and very cheaply too, at M$ 1.50 per bundle. Each bundle is enough to make three cups of herbal tea. It is quite pleasant to drink. I have tested it on myself, but as I do not have high blood pressure, I cannot vouch personally for its efficacy. However, I hear that this plant (a weed in wet places, easily propagated by cuttings)is now being sold in wet markets all over the country.

Friday, April 04, 2008

GM food and NGO pressure groups

It has been a long time since the last famine in Asia. Now food prices are rising and people are wondering whether there will be a shortage. Where will the next technological advance in crop productivity come from? Has the time come for GM (genetically modified) food?

If there is a choice between hunger and GM, there is no doubt GM will win the popular vote.

The anti-GM lobbies, which have run a successful campaign for two decades will soon be facing a crisis. As a scientist, I think the anti GM lobbies have been running an unreasonable campaign based on fear. A reasonable approach would have been to insist on strict regulation, safety tests and compulsory labelling.

When I was working in the FAO (Food and Agriculture Organization of the UN) and CIFOR (Center for International Forestry Research) I was dismayed at how NGO pressure groups in Europe had hijacked the agendas of the development agencies in their countries and had indirectly taken control of the FAO, CIFOR, and other international agencies that depend on funding from those countries. Asians like myself in these organizations had very little influence on the direction of programmes, because our own countries were not footing the bills.

I had been an NGO leader myself in the Malaysian Nature Society in the 1970s and 1980s, but we were a home-grown NGO that did not receive any funding from overseas. The language of European-funded NGOs baffled us. They were, from the start, against big business, against the companies that were producing and marketing improved agricultural seeds, against GM crops, against oil palm, against logging. They were for the right of the poor to remain poor. They preached that shifting cultivation was good and sustainable. Subsistence agriculture was, to them, the way of the future (of course not for themselves, but for Asians and Africans). Developmental aid should only be only for the benefit of the 'poorest of the poor', not to help strengthen weak countries. As an Asian I felt insulted, so I quit my well-paid positions.

The NGOs are not entirely wrong, but they are irresponsible in forcing their social theories on societies to which they do not belong. Instead of promoting good governance, consultation, proper enquiry and research, they indulge in publicity-generating pressure tactics and short-cut dead end solutions. They have had relatively little influence in Malaysia and China and none at all in Singapore, but they are everywhere in Nepal, Philippines, Indonesia, and Africa. When I was in FAO, one consultant back from Ruanda was lyrical about how happy and sustainable Ruanda was, with every family cultivating its own plot of land and making do without cash--the root of all evil. This was Ruanda just before it erupted in ethnic strife and blood-letting. Are there more Ruandas on the way?

Friday, March 14, 2008

Post election euphoria

I cannot resist saying a few things about the elections in Malaysia in which the ruling coalition BARISAN won the right to form the federal government again but lost a large number of seats. It also lost control of 5 of the state governments. Right up to the eve of the elections, I was getting email and sms messages from people to vote for the opposition. I only got one message to vote for the BARISAN. There were legions of passionate supporters of the opposition, only a few lukewarm supporters of BARISAN. The BARISAN could not inspire volunteers to its cause. All its supporters expected to be paid, either up front or later in the form of rewards. On TV and in the streets, those who spoke for the opposition were more coherent, more intelligent and more convincing than those who spoke for the government. BARISAN lost the young, the intelligent and the passionate.

Monday, February 18, 2008

Ramin surprises

Ramin (Gonystylus bancanus), a timber exported by Indonesia and Malaysia, is at the centre of a controversy over whether the species should be banned from the timber trade. Ramin grows in peat swamp forests and such forests are disappearing because after extracting the timber, the swamp is often drained, and the land converted to agriculture. There is no incentive to save the forest because the ramin fails to regenerate. After 50 years of research, foresters have not figured out why ramin does not regenerate in nature.

Curious to find out more, I purchased 8 saplings (4 ft tall and rooted in polybags of clayey soil) from the FRIM nursery and took them home for observation. I placed them under a small tree in a row, watered them well, and went away on holiday for two days. It did not rain during those two days. When I came back, I found to my great surprise that the tough leathery leaves of the plants, especially of the four plants closest to the edge of the shade, had begun to dry and curl up. Six leaves had already been shed on the ground. I watered the plants liberally, but next day, another 60 leaves were shed, including leaves that had re-absorbed water and looked healthy. Next day, three more leaves were shed and the day after, another three were shed. The shedding stopped after that. By then two saplings had shed most of their leaves, one sapling was totally bare, and one had a few dry and dead leaves hanging on it.

Before interpreting these observations, let me digress a little. When a tree is stressed from shortage of water, it has three levels of reaction. If the stress is not severe, the tree recovers when watered and does not show any damage. If the water shortage is more acute, the tree forms an 'abscission layer' at the base of each leaf stalk, which has the effect of cutting off the leaf. By cutting off its leaves, the tree saves itself from drying out. If the drying is sudden and drastic, there is no time for abscission layers to form, and the leaves dry up and die on the tree.

Incidentally we can tell a lightning-struck tree from a tree dead from disease, because in the former the leaves are not shed whereas in the latter, they are.

In the case of my ramin plants, the four better-shaded plants recovered on watering. Of the four more-exposed plants, the one with dead leaves hanging on it is probably dead. The other three, having shed all or most of their leaves, are now stable and should recover.

It has certainly been a surprise to me that ramin is so sensitive to water stress. This is has not been reported before, but then, not many foresters take their experiments home and watch them closely.

Wednesday, January 16, 2008

Digging tools for the garden: fork versus changkul

Farmers and gardeners in Asia use one general purpose tool for digging, lifting soils, leveling the ground, and slicing off weeds at ground level. This is called the CHANGKUL in Malaysia. In the hands of an expert, the changkul is a very versatile, precise and cheap tool. For the the amateur, the European garden fork is a much better tool for digging. You place the fork exactly where you want dig, before pushing it into the ground. For lifting rhizomes and tubers, nothing can beat a fork.

The European garden fork has never caught on in Asia. Because a fork works like a lever in turning over heavy soils, the steel teeth and wooden handle must be able to absorb strong lateral force without breaking. Good forks are made of high quality steel and special timber. It is a curious fact that despite the abundance of timber species in Malaysia, only one Malaysian timber has ever made the grade as a resilient tool handle. This is 'tempinis', Streblus elongatus, formerly used for shoulder poles ('kandar' sticks)used in carrying heavy loads on the shoulders. The loads were balanced one at each end of the pole. This timber is no longer in the market, for lack of demand.

We won't moan the passing of the kandar stick, but it is a pity nobody is interested in improving the quality of locally-made hand tools, and bringing tempinis back into production.

Thursday, January 10, 2008

Managing a grapevine in the humid tropics

In a mediterranean climate, grape vines are pruned back drastically after the grapes are harvested. The vines live through the winter in a leafless condition. Then in the spring, they produce new growth, in the process bearing leaves and flowers.

In the humid tropics, vines can grow throughout the year, but produce only leaves. I have found that when the vines are pruned back drastically and deleafed by hand, new buds will sprout after two or three weeks. If flowers are produced, they will be produced on inflorescences located in a very specific place: adjacent to the third leaf at the time of new growth. Nowhere else and at no other time! If the opportunity is missed, there is nothing to do except to give the plant a few months to grow and then repeat the process. Flowering is not guaranteed but you get another chance with each flush of new growth.

Unfortunately, my grapes are small and sour.

Thursday, January 03, 2008

Solitary passionfruit bears fruit

According to the textbooks, solitary passionfruit plants will not bear fruits, because they require cross-pollination. A solitary plant that I am growing on a rooftop garden in Kuala Lumpur, seven storeys above ground, and far from any other passionfruit bears abundant fruits. The species is Passiflora edulis. I expect the seeds will produce self-fertile plants. I would be happy to send seeds to anybody who would like to try.