Strange brown tree ferns

Sundarbans NP, Bangladesh

27.01.2012

When we were sailing to the national park, I noticed in the distance some tree trunks with an unusual light brown aspect. Later, during our small boat trips along the creeks I had the change to have a closer look. Indeed, some tree trunks were densely covered with large brown leaves.

Mangrove tree trunk covered with leaves

Some of these leaves had been under water and had a ghostly aspect.

Leathery leaves covered with dust

Emu [this is short for Emamul], our very knowledgeable guide, told me that they were epiphytic ferns which in the rainy season turn green. Now this was rather interesting.

Coincidentally, by the time that we arrived in Cochi, Kerala, S India, I came across them in some trees.

Large street trees festooned with ferns

The ferns gave the trees a strange somewhat untidy aspect to these majestic trees though. In Cochi, unlike in the Sundarbans, there were some rather tall trees.

Looking closer at the tree trunks, there were some long ferny green leaves, rather different. The same plant?

Two distinct types of leaves

I asked around and was told that indeed they were the same plant. The oakleaves are the first to appear; they form a kind of protection/support for the longer green ones. See below a baby fern that I found on wall in Kumili, also in Kerala.

Very young fern growing on a wall

What was it?
The mystery was solved when I saw their photo in the book Traditional Uses of Ethnomedicinal Plants of the Chittagong Hill Tracts, it was the oakleaf fern Drynaria quercifolia, a dimorphic epiphytic fern! It is a humidity loving plant, hence the growth of fresh green leaves during the rainy season. By the way, Ripon gave me this book, a very nice present.

Their range outside Bangladesh covers India, Sri Lanka, Malaysia to Polynesia and tropical Australia. I'm just rather surprised that nobody has made a Wikipedia page for such an interesting plant!