Tom's Blog

Thursday, September 15, 2016

The orchid Spiranthes ovalis at Pleasant Valley Conservancy.

Spiranthes ovalis is a relatively uncommon member of the Orchid family. In Wisconsin it is a Special Concern species with a C value of 10.

The Wisconsin Herbarium has a few collections made some years ago, all from Grant County, and a population was also recorded in 2013 from Waukesha County. (See Carter and Pace paper in The Michigan Botanist, Vol. 52, pp 105-108.) The Wisconsin Natural Heritage Inventory also shows this species in a few other counties in southwestern Wisconsin. However, all of the sites where this species has been observed are very small, making conservation of this species the highest priority.

In a recent visit to PVC, Scott Weber and Muffy Barrett of Bluestem Farm discovered S. ovalis in our bur oak savanna. 

Spiranthes ovalis close-up; Scott Weber photo 9-10-2016

This small population, 7 plants, was almost buried among tallgrass savanna, but the tiny plants were erect and healthy. 

Single plant (arrow) surrounded by tallgrass savanna
You have to look carefully to see these tiny plants among the lush savanna understory

Later Kathie and I discovered another small population (4 plants), also among the bur oak savanna.
Spiranthes ovalis in a rocky dolomitic habitat near a remnant population of lead plant

 More sites may well be present, but because of the tall lush grass and forbs at this time of year, it is difficult to search for such tiny plants. You have to stumble on them.

According to the Wisconsin DNR, this species is found in “open bur oak-shagbark hickory forests on dolomite”. This is exactly the habitat where the PVC populations were found.

We had seen Spiranthes plants a few years ago but thought they were the more common S. cernua. It took a visit from Scott Weber, an orchid expert, to recognize what we had.


Blogger Chris Noll said...

Fantastic find! I wonder if they blew in on a westerly breeze or had just been hanging on vegetatively all these years?

September 15, 2016 at 8:26 PM  
Blogger FrankOnABike said...

What differentiates these from other Spiranthes? I found a ladies tresses growing right in the mowed path near the eastern rock outcropping on Sunday.

October 4, 2016 at 6:23 AM  
Blogger Tom's Blog said...

There are quite a few species of Spirathes. This one was identified as ovalis by Scott Weber, who is an orchid specialist.

October 5, 2016 at 9:00 AM  

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