Bangkok Post reader and fellow plant lover Terry Commins shared on Facebook the fun he has had observing how many forest trees time their flowering with the rainy season. "Those with hard seed pods that take longer to mature tend to flower earlier," he wrote. "Each species has its own clock, but almost all end up getting it right for when to drop their seeds to maximise the weather conditions. Some seeds remain fertile for only a day or two, while others can last a year. Enjoy the complexity of nature."
THROUGH THE CRACKS: A fig tree grows in a wall, having been deposited there through bird droppings.
Trees dropping their seeds at just the right time is their way of preserving their species. Seeds with a short fertility period will not be able to germinate if they are dropped in the summer, when there is no water to sustain them. Some seeds are equipped with wings so that they can be dispersed for long distances, where they have a better chance of germinating. Others have a shuttlecock structure, and spin as they fall away from the parent tree. However, sometimes they can fly or spin only as far as the next tree; when a seed collides with the branch of another tree in mid-flight, it loses its balance and falls to the ground. If it falls where conditions are favourable, it germinates and grows to seek its place under the sun in the forest canopy. Most, however, decompose without seeing the light of day.
In my compound I often find plants sprouting where I did not plant them. These are either pink tabebuia (Tabebuia rosea), known in Thai as chompoo panthip, or Indian cork tree (Millingtonia hortensis), aka peep. Both have seeds equipped with paper-thin, almost transparent wings on either side which, aided by the wind, serve as gliders that bring the seeds to my compound from trees in the neighbourhood. Both trees grow fast, but while the Indian cork tree is a straight, evergreen tree that grows up to 15m, pink tabebuia is a sprawling, deciduous tree up to 25m high and therefore needs a lot of space. If I had allowed all the seeds that had sprouted over the years to grow into trees, my compound would have become a forest by now.
Wind is a great dispenser of seeds. Fern spores have no wings or other special mechanisms but they are so light that they can be easily carried by the wind. It surprises me no end that oil palm trees serve as hosts to several species of ferns even in places where no sources are apparent. Where did the ferns come from? On our farm, ferns grow in bromeliad pots even though the greenhouses containing the bromeliads are quite a distance away from the ones housing the ferns. How did the ferns get there? In the forests, wild orchids we see on the branches of trees also grow from seeds blown there by the wind.
Sometimes, we see fig trees growing on pavements or even in cracks on walls. The seeds were carried there not by the wind, but by birds which fed on the fruit then dispersed the seeds through their droppings. A fig can grow even on the branch of a tree, where it grows as a seemingly harmless epiphyte, drawing sustenance from leaf detritus. During the early stage of its life, it grows slowly, gradually extending its roots downward or around the host tree's main trunk. Once the roots reach the ground, the fig grows with increased vigour and surrounds the trunk of the host tree with more roots, strangling it until it dies, leaving the fig standing in its place.
Seeds also can be dispersed by water. The most remarkable example is the coco de mer, which has the largest seed in the plant kingdom.
It is endemic to the Seychelles, where fruits that fell from the tree ended up in the sea and drifted eastwards to Maldives, where they were gathered from the beaches and grown as an important crop. It was in Maldives where the tree was first found, and given the scientific name Lodoicea maldivica, or Maldive coconut. It was only much later, when Seychelles was discovered and it was established that coco de mer in fact originated there, that the palm became known as Seychelles coconut, but the scientific name remained.
We in Thailand, however, are more familiar with the coconut (Cocos nucifera). When ripe, the fruit has a very thick, fibrous husk that enables it to float for long distances in the sea. It can germinate if cast well above the shoreline during high tide, which is probably the reason why coconut trees can sometimes be seen growing along coastlines even on uninhabited islands. Another remarkable fruit is that of the Rhizophora, a kind of mangrove tree common in Thailand. The fruit is not large and contains only one seed, which begins to germinate while still inside the fruit. The roots of the seedling pierce the skin of the fruit and hang downwards, and once the seedling is fully grown, it separates itself from the fruit and drops off. If the tide is low when it falls, the roots are embedded in the mud and the seedling is planted. If the tide is high, the seedling falls into the water and is carried away by the waves.
Last week I was in Phuket and visited a friend who owns a tree plantation. As we walked around to see her trees, I noticed seeds of the weed known in Thai as ya chao choo clinging on our pants. As the rains have not yet abated in the South, I am sure the seeds will grow where they were discarded. The greatest seed dispenser of all is man, and the reason there's a wide diversity of ornamental plants in Thailand is that since the time of King Rama V, who was an avid plant lover, Thai enthusiasts have been bringing home plants and seeds from their travels abroad. During her visit to Seychelles, my friend brought home a coco de mer nut which she planted in her garden in Phuket. Only four leaves have so far emerged from the ground, yet the plant is already several metres high. A fully grown leaf with its stalk alone is more than twice the height of man. However, it will take 25 years for the tree to bear fruit _ if it is a female, that is _ and be propagated for others to enjoy as well.