15 September 2014

Orchids Are Weeds

Okay, so maybe saying that orchids are weeds is a bit of a dramatic exaggeration.  However, while mowing the trails on our St. Joseph County, Indiana property yesterday, I had to slam on the brakes inches from mowing the fourth orchid species that we've documented on our property, October Lady's Tresses (Spiranthes ovalis var. erostellata). If you're a follower of this blog, you may know that the previous three orchids we'd found on our property were Ragged Fringed Orchid (Platanthera lacera), Purple Twayblade (Liparis liliifolia), and Green Twayblade (Liparis loeselii).  After finding the third of those, I asked readers of this blog (tongue in cheek) which orchid species we would find next.  Keith Board has to win some kind of prize for predicting that we would find this species.  My find today is even more interesting because I saw this species growing on the St. Joseph and Elkhart county line on Friday last week and came home to look for it on our property in a young successional wooded area.  I struck out.  I guess I was looking in the wrong place and instead needed to be sitting on a riding mower to find it.

Sure, a weed is often defined as a plant out of place.  In that sense, I don't necessarily consider orchids weeds.  However, the more I see and learn, the more I think that many of our orchid species require disturbance to grow, reproduce, and continue to be evident above ground, and without that disturbance, they cease to exist (at least until the disturbance returns) (see the dialog in the comments of this post for a discussion on this topic).  In this case, the orchid I found is growing right at the edge of the trail that I mow regularly, in old-field, with mostly non-native species and weedy native species such as Tall Fescue (Schedonorus arundinaceus), Riverbank Grape (Vitis riparia), and Poison Ivy (Toxicodendron radicans ssp. negundo). 

As seen in the photograph below, the flowers of October Lady's Tresses (also known as Oval Ladies'-tresses) are usually in three spiraling ranks.  The flowers (and specifically the lip) are smaller than many of the other members of the genus Spiranthes, with the lip reaching only approximately 5.5 mm; the other two species that have flowers that minute in the lower Great Lakes region have either a yellow or green spot on the upper surface of the lip.  The lip on October Lady's Tresses is quite recurved and is usually inrolled, giving it a narrow appearance. Another good field character used to help identify October Lady's Tresses is seen in the photograph above... notice that the leaves are present and conspicuous when the plant is in flower. 

Whereas many of our Spiranthes grow in full sun habitats, October Lady's Tresses is more shade-tolerant and does best in openings in woods, along trails, and in young successional woods.  It also is found in thickets and in old-fields.  When forests mature and less light can reach the forest floor, this species tends to be less prevalent, an indication that it requires disturbance. You can see the habitat where I found the plant on our property in the photograph below (it is just about in the middle of the photo).  Not an area that anyone would consider "high quality" by any means.

The range of October Lady's Tresses includes the eastern United States and the province of Ontario.  However, it is not known from more than a large handful of counties in any of the states in which it occurs, and its county distribution is fairly even over its range.  That said, this species is increasing its range and distribution, likely in part due to the increased level of disturbance to our natural areas.  So... is it just a weed?  Certainly a unique and welcomed one on our property!