The peculiar case of the maroon bat flower
An excellent indicator of rainforest-like habitats in northern Thailand is the bat flower, Tacca chantrieri. Here in the seasonally dry Chiang Mai it grows in evergreen areas, and then only along streams in dark environments. At Dokmai Garden we grow it behind the large forest mango and we help it thrive with misting. In the wild I have seen it in the nearby Opkhan national park and the Mae Khanin Tai area. It is possible these populations are isolated remnants of a wetter period. The species is predominantly reproducing by self fertilization.
Due to its weird flowers which look like nothing else on this planet, it has been placed in its own unique family Taccaceae. There are only ten species in the world, five of which are native to Thailand. Recently it was merged with Dioscoreaceae (the wild yams) based on DNA analyses showing its pedigree. As plant families are a matter of subjective convenience for grouping plants with similar traits, the name ‘Taccaceae’ is still useful, although the evolutionary origin of the genus is of great interest.
When we do orchid scouting for the Orchid Ark (i.e. record the natural habitats of wild orchids) we always make a remark if the orchid is found near Tacca, which implies a very moist condition. Is it a rain forest? The original term referred to an ever wet forest, but such forests are very rare on Earth so the term was expanded to encompass tall lowland forests with a minimum of 1800 mm of rain per year, maximum four weeks of drought and no leafless period. With that definition rain forests do not occur anywhere in Thailand. The term is still used of prestige for any tropical forest, but I believe it is better to expand people’s understanding of tropical forests by using the term ‘jungle’ or ‘monsoon forest’ for the seasonally dry and wet forests that surround Chiang Mai. We have real jungles, equally biodiversity-rich as the rain forests, but different, and that is something to be proud of too.
For the avid Chiang Mai gardener who is looking for something to plant in his shadiest spot, with large, glossy dark green leaves and peculiar blossom, the bat flower is a good choice (if watered generously). If they disappear, do not despair, this local species have the ability to withdraw if it gets too dry and survive as a perennial tuber.
I think the cut flowering stalk is most ornamental if kept in a wooden room. The hanging flowers and the bat wings (modified leaves called bracts) have the same shade of dark maroon as the furniture and floor of the Dokmai Garden teak house. As seen here the individual flowers are arranged in a cluster (an umbel or cyme). The six petaloid tepals are erect or reflexed. What looks like ‘balls’ inside each flower are the six male stamens covering the female stigma in the centre.
The ‘whiskers’ are according to some authors sterile flowering stalks (pedicels), others consider them filiform bracts (bracteols). Why the bat flower has such whiskers is unknown to me. Maybe they have a similar function in Strophantus (Apocynaceae) flowers, where the petals are elongated into ‘whiskers’, possibly enabling special climbing insects to pollinate? Flies have been mentioned to be natural pollinators. Does any Dokmai Dogma reader know?
An anatomical overview of Tacca flowers can be obtained from ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 18th May 2012.’
Tacca is the Latinized form of a Malayan word for this plant. ‘Chantrieri’ refers to the Chantrier Frères (the brothers Adolphe and Ernest Chantrier who created a horticultural plant nursery in 1871). This company is still in business! That scientific name was coined by the French landscape architect and head gardener of Paris; M. Édouard-François André (1840-1911) in 1901.
Text & Photo: Eric Danell