After the Botany conference I travelled to upstate New York, where I used to live, and where there is an abundance of Dryopteris species (if only I'd known while I still lived there...). I visited several preserves and state parks, some of which I hope to use as field sites for additional physiology studies to be conducted next summer. One of my favorite places is Thurber Preserve, since it was there that I saw D. clintoniana for the first time. I wanted to go back to check on the population and make sure it would be healthy enough to withstand a few measurements next summer, and I was delighted to find that the ferns are doing great! The population was larger than I remembered, and spans the edge of the swamp from forest to thicket, mostly in the shady areas. Wherever direct sunlight hit, that seemed to be the boundary beyond which D. clintoniana would not trespass.
This species is a polyploid, and the only hexaploid known in the North American Dryopteris complex (it has 3 duplicate genomes). Its putative parents are D. goldiana and D. cristata, the latter of which is a tetraploid (two duplicated genomes... so D. clintoniana has 2 from D. cristata plus 1 from D. goldiana and you have 3). This species most closely resembles its D. cristata parent, except that it is gigantic in comparison. It gets the size boost from D. goldiana. Notice in particular the horizontal arrangement of the pinnae in the photo below... the clear hallmark of D. cristata.