willow will sprout from virtually any cutting. in NZ it is an introduced species brought in as fence post which sprouted. So the story goes, they should have been planted upside down to prevent acting as a cutting. Though according to Joy (a gardner) it will sprout even if planted upside down.

I lopped the tops off trees in NZ and planted them (4 inch dia) to a depth of 2 ft. Within 2 days they had more vigourous budding than when on the top of the original trees.