by Robert Connell Clarke
Rooting Media
Water is a common medium for rooting. It is inexpensive, disperses nutrients evenly, and allows direct observation of root development. However, several problems arise. A water medium allows light to reach the submerged stem, delaying etiolation and slowing root growth. Water also promotes the growth of water molds and other fungi, supports the cutting poorly, and restricts air circulation to the young roots. In a well aerated solution, roots will appear in great profusion at the base of the stem, while in a poorly aerated or stagnant solution only a few roots will form at the surface, where direct oxygen exchange occurs.
If rootings are made in pure water, the solution might be replaced regularly with tap water, which should contain sufficient oxygen for a short period. If nutrient solutions are used, a system is needed to oxygenate the solution. The nutrient solution does become concentrated by evaporation, and this is watched. Pure water is used to dilute rooting solutions and refill rooting containers.