Yes, like all "mountain mints", somewhat of a misnomer, in that it is, as you said, a true prairie plant. Your find is one I've not yet seen here in WI though it is native here as well. I've only ever come across P. virginianum.

BTW, I admire your patience in counting those plants! Also, I see no reason why this species would not be happy in a sandy soil. They prefer good drainage, and voila-sandy soil usually drains well.

+oM

This is one of the more aggressive native plants in my garden, though not unmanageably so. To me it has only average ornamental value. I like it mostly because it seems to attract a lot of insects, stands up straight, and needs no babying. I think I may eventually divide and move it out of the front hell strip bed to a more out of the way location where its expanding nature will be more welcome.

I'm not sure I would agree with "true prairie plant" -- at least not to the same degree as, say, Hesperostipa spartea is a true prairie plant, one whose range is restricted mostly to the prairies of the Midwest and High Plains . But perhaps I'm taking too narrow a view of prairies. My understanding is that there are (or were pre-settlement) a lot of open areas in the Appalachians -- limestone barrens/glades where C4 grasses are common. I would guess that P. tenuifolium spread from there into the parts of the country where prairies are predominant.

I won't split those hairs, Woods. In fact, the only time (thus far) that I've run across Pycnanthemum v. is in planted prairies we've installed around many of our community's stormwater management practices. Since some of these sites involved wetland mitigation, I am the person who does the mitigation monitoring reports which subsequently are submitted to the Army corps of Engineers and our DNR. As such, my plant ID'ing skills have been honed a bit, compared to where I was at previously. And for what it's worth, while these prairie plantings do good service to both the community-woody vegetation is taboo in 100 year floodplains as it doesn't bend over and allow water passage-and to nature herself-these end up being huge habitat zones-this is not the primary original plant community for the area, it having been heavily forested prior to right around the 1840s.

+om

Thanks for the comments. I have looked in many other places nearby and there are no other populations of P. tenuifolium. I guess this plant must have been a lot more common in the 1800's when there was less tree cover and lots of fields.