In the tops of plants, plant hormones or -growth regulators (auxins) are created under the influence of light and heat; which are transported to the part of the plant, where the roots are or should be located. Therefore, in the summer the production of these hormones is better than in the winter. Therefor the best chance of rooting of cuttings is normaly the period between April to July. Outside this period the success of rooted cuttings becomes more difficult and often depends on the weather. By using external growth substances cuttings will root better and faster.

In most root forming stimulators, the active substance is Indole-3-butyric acid powder with a content of 0.25% to 1%. Because of its composition powder has a slow releasing effect, which often gives better results than cutting agents in wet (gel) or tablet form.