We have here, in quantity, a certain daylily. We have always referred to it as the ‘Double-ditch’ for obvious reasons and assumed that it was an unnamed oddity. Well, what should I find in a gardening catalog today? (Old House Gardens; www.oldhousegardens.com)
H. fluva ‘Kwanso’ circa 1860
Here it is at Esperanza
Acair Fearann 
when I moved from the coast to Raleigh, NC which is more in the central Piedmont plain, all of the orange ditch daylights became double. Very strange.
Strange! we have the standard single orange here as well, in even greater numbers. I suspect they probably cross back and forth quite happily; but I have never seen the double growing wild on the roadsides in this area, only in the remnants of the original gardens here. It may not be quite as good at naturalizing this far north.