More growing

Talking about the weather and things growing (which I'm sure we were at some point, keep up...), what do you call those things that look like caterpillars but are really the fronds of ferns unfurling?
This morning was wet and miserable, a real stay-at-home morning, a proper dog-won't-mind-if-we-don't-go-out-for-a-walk morning. It was meant to settle in for the whole day, so we placed bets on the horse races being shown on the telly*, including the Derby, but instead in the afternoon we found ourselves strolling through the woods in the warm sunshine, looking at the ferns spurting growth.

* Suffice to say, it's back to work on Monday (winnings minus stakes = loss).