On the other hand, the visible evidence of plant-insect or plant-animal mutualism have long been observed. The most significant example of symbiosis is pollination, a process entirely dependent on the co-operation between bee and flower, but there are hundreds of lesser-known examples. Small bats hide in the deep cups of nepenthe flowers and in the process provide nutrients for their host, clown fish enjoy the protection of anemones and return the compliment by keeping them free of parasites.
Back to plants. Vines provide an interesting study. In the wild, their seeds fall to the ground, usually in densely wooded terrain, but they lack the lignum in their flexible but weak stems to force their way, unaided, up to the forest canopy. Not that these vines do not need sun; they most certainly do. So how do they cope? By the expedient of using their surplus energy, not to form stiff, woody stalks capable of supporting themselves, but to create thin, adaptable stalks that cling to the rigid trunks of trees and thereby ascend, quite literally and relatively effortlessly, to the light.
If you walk into a broad-leaved tropical forest, you will see this process everywhere at work. But the process is not always a symbiotic one, not always mutually beneficial. While the liana benefits hugely – indeed, it would die without some access to support and sunlight – it does inevitably compete with host trees for water, nutrients and above all sunlight.
You may be wondering what lianas are. In brief, the term is a generic one – and applicable to hundreds of different species of climber – a blanket expression for all those jungly vines that corkscrew round the boles of trees, or attach themselves to their host by tendrils, suckers or spines. And these climbers are versatile: they can form bridges across the forest canopy or snake along the ground in search of a high-rise neighbour. Handy for small arboreal animals such as squirrels or lemurs, but less good for the trees which sometimes succumb to the suffocating embrace of the invading vine. And some of these lianas are monsters. One climbing variety of bauhinia (orchid tree) was measured at 600 metres long.
Though these lianas are generally a nuisance in the wild, inhibiting the growth of rain-forest trees, gardeners, ironically, want them to thrive – in the form of cultivated varieties of flowering vine that will grace any pool-side setting. They want their Rangoon creepers, bougainvilleas, and coral vines, their argyreias, and mansoas to show off their blossom power. Upwards and onwards.
We gardeners do not pine for a patch of jungle in our plots to encourage our flowering vines, but if we want to get the best out of them, we will need to provide support, either naturally in the form of small trees, or by employing such man-made structures as trellises, fences, pergolas or walls.
I recall a couple of examples. A Kata resort has a bougainvillea at the end of its driveway. The largest ‘fueang fa’ I have ever seen – fully 60 feet tall, it is normally in glorious flower. The reason for its size? The host tree which supports it, now so upstaged by the climber that I cannot even identify the variety.
Finally, an instance from my own garden. While it was an unplanned marriage, you can see from the illustration that such a combination can work. The two plants in question are an allamanda carthartica, long one of my favourite climbers, and a crepe myrtle tree. I use the word ‘climber’ advisedly because although the allamanda is a climber by instinct, it lacks the specialised devices – suckers, hooks, spines or tendrils – available to more efficient vines, and possesses, in addition to its massive golden blooms, substantial stems, buds and foliage. In other words, it is a heavyweight that needs support; without it, the whole superstructure will end up as an untidy mass.
As chance would have it, my allamanda was planted next to the garden gate in the company of a crepe myrtle, an erect and vigorous tree that needs frequent pruning, but which does sport pleasant pinnate foliage and, in season, clusters of mauve flowers. Grateful for the unexpected proximity, and with a little help from my friends, the vine managed to attach itself to the myrtle’s branches and has since enjoyed its extended day in the sun. They both seem quite happy. Mutualism at work? Well, maybe…
Patrick Campbell’s book ‘The Tropic Gardener’, described in one Bangkok review as the best book on Thai gardening for 50 years, is available for B500 (half price) to personal callers from 59/84 Soi Saiyuan 13 in Rawai (Tel: 076-613227 or 085-7827551).