Since certain chemicals are capable of enhancing root production on a stem cutting, it is possible that other techniques may also cause a surge in natural hormone production that could improve rooting.
In some plants there exists in the stem between the bark tissues and the wood tissues a sheath of material that is capable of inhibiting root development. However, when part of this sheath is damaged, then roots will be produced normally. This damage is achieved by a technique known as wounding.
The commonest method of wounding is to remove a slice of bark from the bottom inch or so of the cutting, using a sharp knife so that the wood tissues are just exposed. Alternatively make three or four 1 in long incisions in the bark at the base of the cutting as deep as the wood tissues.
The technique of wounding can be very effective with rhododendron, daphne and juniper, but it is unwise to use it as a matter of course as it provides another possible site for infection and rotting. It may only be necessary on older, hardwood cuttings; softwood cuttings do not normally require wounding. The need to wound a cutting will only be discovered in the light of experience—a continued failure to root a cutting, which cannot be attributed to any other cause, may then suggest that the cutting may respond to wounding.
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