Wednesday, November 20, 2013

To bloom before dying, the precarious life of twig epiphytes

A Dendrophylax that is in a piece of bark the tree has shed sends a root toward the nearest branch
A Miconia tree trunk showing the bark that is about to be shed.
This Leochilus is kept in place by its numerous roots even though
the base of the plant is not attached to the tree

In trees that don't shed their bark the branches can become literally
 carpeted with all manner of epiphytic plants

Tillandsia seedlings in a twig of an orange tree

A Campylocentrum has found a favorable spot on a branch and is fruiting heavily.  The Ionopsis on the smaller branch will probably fall along with the dead branch in which it is growing.
Most people picture the life cycle of epiphytic orchids as one that is fairly sedate.  They have the impression that once an orchid germinates in a tree it can spend decades growing and blooming seasonally with little change to its circumstances.   This is true for many species, but not for all.   In particular, the life of orchids that prefer to grow in twigs is a race to bloom before the tree sheds the bark or the twig dies.

Why would an orchid grow under such precarious circumstances?  My own guess is that these orchids are exploiting a niche where they face little competition from other plants.    I have observed that the local orchids sometimes develop such extensive root systems that they alone can keep the plant attached to the tree when the twig or branch dies.  Also, they seem to bloom while quite small, no seven year wait to reach adult size and bloom with these orchids.  However even with all these adaptations life is precarious for these orchids, if one walks on the forest after a particularly windy storm it is common to find fallen twigs often with Ionopsis orchids on them.  In the forest around my house you can find Dendrophylax, Ionopsis, Campylocentrum and Leochilus in the branches of Miconia and Guava trees.

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