Stim-Root, like other rooting hormones, will not make roots grow, rather it enhances the plants own ability to produce roots by supplying plant hormone at the point of rooting to help initiate root development.
Use Stim Root #3 - 0.8% Indole-3-butyric acid IBA for harder/woodier cuttings.
Stim-Root #3 is specially formulated to encourage the quick establishment of roots on hardwood plants. Like other rooting hormones, will not make roots grow but enhance the plants ability to produce roots.