Lady’s Tresses Orchids in Prairie Seedings

I love mysteries. 

I don’t know much about orchids, but my understanding is that they can be difficult to establish in restored (reconstructed) prairie, largely because they rely on mycorrhizal fungi that are unlikely to be present in soils after years of row crop agriculture.  Regardless of that information, or maybe because of it, (I can be somewhat obstinate) we keep harvesting seed from nodding lady’s tresses orchids (Spiranthes cernua) whenever we can find the plants after they’ve gone to seed in the fall. 

…and darned if they’re not showing up in our prairie seedings!  To date, I’ve found Spiranthes in at least four separate prairie seedings in our Platte River Prairies.  When I saw the first plant, I came up with all kinds of explanations for how it might have occurred, none of which included our seed (there was some bulldozer activity near where the plant was, so surely some plant material and soil came in with the dozer…).  By the third and fourth sites, though, I finally came around to the idea that the plants had to be a result of our seed.  I’m still not sure of that, but it’s pretty hard to think of other reasonable explanations.

We've found nodding lady's tresses plants like this one in at least four prairie seedings now. Those seedings were planted in 1995, 1995, 1997, and 1999, respectively.

So – what’s going on?  Is there something special about the sandy loam soils that allowed myccorhizal fungi to survive many decades of row crop agriculture?  Are those fungi somehow making their way into the soils once prairie vegetation establishes?  Are orchids less reliant on those fungi than we thought – or maybe just able to use a wider variety of fungi species than we thought?

I don’t have any answers, just lots of questions.  I’m hoping to hear from some of you about your experiences with Spiranthes species in prairie seedings.  I’m also hoping that some of you know more about myccorhizal fungi than I do (I still have to check the spelling every time I type it…) and can explain what I’m seeing.

Help?