Look Ma! No Leaves!

This past weekend, a colleague and I were visiting an area in central-west Florida that is host to one of Florida's rarest endemic orchid species, only found within our state as far as anyone knows - Triphora craigheadii. It is likely that it grows elsewhere in tropical America, but its small size and secretive habit makes it very difficult to see. This same site hosts a number of plants of Copper Ladies Tresses (Mesadenus lucayanus), which were in bud, but not yet in flower, their slender coppery spikes blending in quite well with the fallen leaves. As we were poring over the site, looking to see if any T. craigheadii remained aboveground, we spotted some other coppery-colored spikes in full bloom. These, however, belonged to a completely different species, Corallorhiza wisteriana, also known as Wister's Coralroot or the Spring Coralroot. This plant is most notable in that it lives its entire life without ever growing a single leaf, relying instead on a special relationship to survive.

Most monotocotyledonous plants, such as corn and wheat, include a healthy dose of energy-rich starches in the seeds, which is what makes them useful to humans as a food source. As you may or may not be aware, orchid seeds are small and dust-like, containing only an embryo wrapped in a thin sheath without any nutrients added to the packet to get the seedling started on its new life. These seeds, in order to germinate, must fall in an area where specific fungi are growing...these fungi then begin to infect the seedling, and in the process begin to funnel nutrients through their mycelia into the plantlet. Thus, the orchid seedling begins its life in complete dependence upon the fungus. As the seedling grows, it typically develops its own leaves and begins the process of photosynthesis to produce some or most of its own nutrients. Its roots, however, will continue to host a population of these fungi, consuming bits of fungus at times, in a relationship termed myco-heterotrophy.

Coralroots are part of a unique group of orchids termed saprophytes, which continue to rely almost entirely on this fungal relationship for the necessary nutrients to live and grow. This particular species grows rather large underground root structures to host its fungi, which look a bit like a branching marine coral, hence the common name. The only clorophyll these plants ever produce is in very small quantities in the above-ground flowering stems, which come up briefly in the spring, to set seed and die back before a month has passed.

Their small flowers have a definite reptilian quality, looking like a number of tiny Cottonmouth snakes striking out at a hapless passerby. They are suffused typically with small purple polka-dots on all the floral parts, which looks particularly striking on the white lip. Here is a photo of one of the plants we saw that day. As we understand it, this was the first time this species has been observed growing at this particular site, probably because the main star here, T. craigheadii, blooms in June-July, and although Mesadenus do bloom here at this time, there is a site nearby where they are much more abundant...hence, I don't think anyone was watching this site at this time of year.


Enjoy!

---Prem