Semi-Aquatic Orchids

 By Jim Fowler. Copyright © 2017

By Jim Fowler. Copyright © 2017

Orchids have conquered nearly every continent on this planet except for Antarctica. In fact, there seems to be no end to the diversity in color, form, and habit of the world's largest family of flowering plants. Still, it might surprise many to learn that some orchids have even taken to water. Indeed, at least three species of orchid native to Latin and North America as well as a handful of islands have taken up a semi-aquatic lifestyle.

Most commonly encountered here in North America is the water spider orchid (Habenaria repens). It is a relatively robust species, however, considering that even its flowers are green, it is often hard to spot. Though it will root itself in saturated soils along the shore, it regularly occurs in standing water throughout the southeast. Often times, it can be found growing amidst other aquatic plants like pickerel weed (Pontederia cordata) and duck potato (Sagittaria latifolia). Because it can reproduce vegetatively, it isn't uncommon to find floating mats of comprised entirely of this orchid.  

 By Jim Fowler. Copyright © 2017

By Jim Fowler. Copyright © 2017

Living in aquatic habitats comes with a whole new set of challenges. One of these is exposure to a new set of herbivores. Crayfish are particularly keen on nibbling plant material. In response to this, the water spider orchid has evolved a unique chemical defense. Coined "habenariol," this ester has shown to deter freshwater crayfish from munching on its leaves and roots. Another challenge is partnering with the right fungi. Little work has been done to investigate what kinds of fungi these aquatic orchids rely on for germination and survival. At least one experiment was able to demonstrate that the water spider orchid is able to partner with fungi isolated from terrestrial orchids, which might suggest that as far as symbionts are concerned, this orchid is a generalist.

The flowers of the water spider orchid are relatively small and green. What they lack in flashiness they make up for in structure and scent. The flowers are quite beautiful up close. The slender petals and long nectar spur give them a spider-like appearance. At night, they emit a vanilla-like scent that attracts their moth pollinators. 

Photo Credits: Jim Fowler. Copyright © 2017 www.jfowlerphotography.com

Further Reading: [1] [2] [3]