Science experiment with pollarded willows

My garden is lined with pollarded willows (It's kinda a historical thing over here.) and some of them have rotted away quite a lot. They can go on in this state for many many years and past experience teached me it's hard to get replacements going where these are located, so I'm not to eager on cutting them down.

I've got the idea to use the rotted mulch as a starter for new branches, just like you would plant them in open soil to get new trees. I'm curious how this will go!