Black willows are a fascinating tree.  Cut and plant a bow in moist soil or water and you’re nearly 100% likely to grow a new tree.  Black willows contain high levels of a growth hormone that accelerates root growth.  This hormone may be applied to other plants as well:  Take a few cuttings (about the size of a pencil each) and soak them overnight in water.  This water may then be used to soak other shoots and will act (as do commercial growth hormones) to accelerate growth of new roots.  It’s an all-natural, old-fashioned method that works.