Does formative pruning improve the form of broadleaved trees?

Abstract

Formative pruning is the pruning of young trees before canopy closure to encourage the development of a single straight stem at least 6 m in height. The use of formative pruning has been widely recommended; however, this guidance lacks a scientific basis. The experiments described here examined the effects of four levels of formative pruning on precanopy closure stands of European ash (Fraxinus excelsior L.), cherry (Prunus avium L.), European beech (Fagus sylvatica L.), and English oak (Quercus robur L.). For the faster growing ash and cherry, two prunings were applied over a 3-year period; for the slower growing oak and beech, there were four prunings over 4–6 years. Form and growth were assessed for up to 9 years after the last pruning treatment. A moderate intensity of formative pruning that removed forks and large branches showed some potential to improve the form of oak and beech. However, there were no form improvements for any level of formative pruning applied to ash or cherry. Attempting to produce the quality of timber required by management objectives by minimizing the number of trees planted and applying formative pruning is risky and likely to fail. A more secure way of obtaining quality improvement is to use traditional pruning after a period of canopy closure.