Missouri Orchids – Corallorhiza odontorhiza (autumn coralroot)

A rare open flower of Corallorhiza odontorhiza (autumn coralroot). Most plants of this species produce cleistogamous flowers that do not open, thus facilitating self-pollination.

Casey and I found three separate populations of Corallorhiza odontorhiza in early to mid September this year, each population consisting of just a few bunches of plants. Most plants of this species found in Missouri are cleistogamous, containing flowers that never open and thus forcing the plant to self-pollinate. This might account for the rather dull colors and patterns on flowers of this species when compared to its vernal-blooming relative, C. wisteriana. Of the three locations, we found only one bunch of plants, located in St. Louis County, that contained open (chasmogamous) flowers and these were slightly more showy than I expected them to be.

Chasmogamous flowers of Corallorhiza odontorhiza with obvious swollen ovaries.

Like C. wisteriana, this species is myco-heterotrophic, parasitizing mycorrhizal fungi to obtain carbon and other necessary nutrients. Consequently, this species never produces leaves. Both Corallorhiza species are found scattered throughout Missouri and can be found in a variety of habitats, but seem to prefer open woodlands on xeric to mesic soils.

Corallorhiza odontorhiza. These are cleistogamous flowering stems that Casey and I monitored from just after emergence. The flowers never opened and ovaries began to swell prior to the flowering stems reaching their full height.

-OZB