Corallorhiza maculata - Orchid of the Month, June 2017

Corallorhiza maculata, Walter Siegmund, GNU licensed at Wikipedia

Corallorhiza maculata (Spotted Coralroot) is a very unusual orchid that grows on the ground in mountain woodlands throughout North America. In my native Pacific Northwest, it is locally abundant - the visible parts of the plants are erect coppery pannicles of small flowers. Close up, the flowers are brightly colored and showy but they are small and when hiking you notice at first the flower spike as a whole. The plant flowers in the spring but when the spikes dry up they stand like dead sentinels for months, so it is easy to see where coralroots grow even when not in flower, despite the fact that the rest of the plant is under ground. The genus Corallorhiza gets its name from the roots, which form dense clusters of stumpy projections, looking more like certain marine corals than our usual idea of roots.

Corallorhiza maculata, by Ron at nativeorchidsofthepacificnorthwest.blogspot

Dried flower spikes, Gerry Carr, Florida Flora Image Project

The flowers are lovely but what makes this orchid unusual is that it is mycoheterotrophic - it parasitizes fungi. Under the ground. Secretly. All over the forest. It is a conspiracy theorist's dream plant. It has no leaves, no chlorophyll, not even a hint of green anywhere. Except for the flower spikes it is invisible. Where I grew up in the Northeast U.S. a more common mycoheterotroph is the Indian Pipe (Monotropa uniflora, not an orchid), but in the Northwest coralroots are much more common.

As you may know, forest soil is packed with fungal mycelia (not the mushroom fruiting body, but the wispy white threads that form most of the fungus). Those fungi are mostly either saprophytic (living on decaying plant material) or mycorhizal (living as a mutualist with live plant roots). Corallorhiza maculata is reported to parasitize Russulaceae fungi, which themselves are mycorhizal with trees and shrubs (and produce Russula mushroom fruiting bodies above ground). The orchid somehow extracts a living from Russula mycelia as a parasite (not a mutualist).

Here is a fungus, which we usually think of as degrading things, being used as food by a plant, which we usually think of as the ultimate biological producers. And an orchid no less!