I was in a fern forest at Volcano yesterday with a visitor, who was admiring the young hapu'u frond's colors. I've never paid much attention to the growth sequence of fronds, but I went around the yard looking for adolescent fronds. There were more than I expected. Here's one of them. I knew, but had forgotten, that the young ones are much more feathery than the older ones. You can see that in the image.