In some species root formation can be promoted by pretreatment with root setting hormones (RSH) before they are inserted in the rooting medium. There are three principal ways of application:
Root setting hormones can be made from a solution of the active chemical (e.g. indolebutyric acid (IBA) or naphthaleneacetic acid (NAA)) or it can be purchased from forestry or horticulture dealers under various commercial names such as IBA, Proportion, Seradix, Rootone, etc. For the specific use of these remedies reference is made to the individual instructions.
Certain precautions and tips when applying Root Setting Hormones are given below:
Sometimes a fungicide can with preference be mixed with the RSH since it will save one work portion.
RSH is best absorbed from a new cut surface. If the cuttings have been kept or stored for some length of time, a new fresh cut should be made.
RSH will deteriorate with time. If a solution has been kept for a long time, its effectiveness should be checked before large scale use. Tomato leaves are sensitive to RSH and therefore good check plants. Treat some leaves with RSH and let them root together with some non-treated leaves.
Concentration and length of time for absorption are critical. Some species will require only a brief treatment with low concentration whereas others may require a prolonged treatment with a more concentrated dilution. Instructions following the individual remedies give guidelines on use for various plant species.
Note: Alcohol is toxic to the plants. Too long time in a concentrated solution containing alcohol may kill the cuttings.
RSH can deteriorate with long time uses. Use only small portions of RSH in a container at the time and then refill.
For rational application, dip a number of cuttings at the time, not one by one.