Orchids Naturalized in the City

Small white flowers of the pigeon orchid

After a regrettably extended respite, including a new laptop made possible by the convergence of tropical thundershowers and forgetfulness, I thought it would be good to share a few more things again. And in an effort to showcase those autotrophs close to my heart, I thought I would talk a little bit about plants this time around. Specifically, epiphytes, or simply plants that grow on other plants. These plants typically rely on the rigid, long-lived branch structures in trees for their support. Although they rely on their hosts for physical support, they do not detrimentally extract nutrition from their partner. In temperate biomes, mosses and lichens mainly comprise the range of epiphytes living on woody tree stems, while the favorable climate and ample moisture of tropical biomes permits innumerable exploitations of this ecological niche. In short, we’ve got all kinds of stuff growing in trees down here! In Singapore, it’s common to encounter various ferns, liverworts, hoyas, and orchids living in tree canopies. We might as well talk about everyones’ favorite, the orchids.

The tree-based weather station

Horticulturists have consistently devoted their enthusiastic efforts to members of the Orchid Family (Orchidaceae), one of the largest plant families. Their beautifully diverse colors and forms have enticed many. Furthermore, the captivating stories of pollination biology, representing cunning reproductive strategies, are inspiring and awesome (see: bee orchid, Ophrys apifera). Species of orchids are native to every continent except Antarctica. They exist mostly as epiphytes in the tropics and as terrestrial plants in seasonal ecosystems (e.g. Cyprepedium parviflorum, Pogonia ophioglossoides, Sprianthes odorata). In Singapore, there were over 200 native orchid species originally recorded, but the total number of native orchids has dwindled due to the high cost of urban development and habitat loss. Recently, Singapore has made an ambitious, long-term commitment to reintroduce and sustain a population of native epiphytic orchids within the city’s managed tree canopy. This represents a real commitment to creating an ecologically-sound built landscape. They have even installed tree-based weather stations to monitor the typical microclimate occupied by these epiphytes!

Tiger orchid flower

There are three common orchid species encountered in the city’s trees, including the pigeon orchid (Dendrobium crumenatum), Bulbophyllum vaginatum, and the tiger orchid (Grammatophyllum speciosum). The tiger orchid is physically one of the largest species in the family, flowering normally once every two years. It’s sheer size at maturity can be astonishing, and there is a great specimen in the Tanglin Core of the Singapore Botanic Gardens.

Pigeon orchid flowers

The pigeon orchid, in particular, has been a successful colonizer of urban trees. It flowers predictably after experiencing a sudden drop in ambient temperatures, but the small, white blooms only last for one or two days. The most recent bloom I witnessed was on the first day of the Chinese New Year, an auspicious sign if ever!

I’ll keep my eye out for newly introduced orchids and post the photographs.