When cuttings of other species were placed in water where the willow stems were held, he observed that they, too, rooted easily. Today, the substances in willow are still not completely understood. They are collectively called rhizocaline and are thought to be three or four different elements or compounds, perhaps vitamins or sugars, that work in association with naturally occurring plant hormones to form roots. Willow appears to have more rhizocaline than other plants, hence its use in propagation. Though it sounds like a miracle worker, willow water probably isn't.
Most professional propagators opt instead for commercial rooting hormones.
Amateurs, it seems, and organic gardeners are most intrigued by the willow. Kristine is trying it on her cuttings and is expecting good results. Making willow water is easy. The hardest part is to find willow branches. Either slice these lengthwise or break them up with a hammer.