The question is sometimes asked whether pruning is good for trees. It may just as well be asked if surgery is good for people. Most people would presumably answer the latter question in the negative. Surgery often is necessary, but is undertaken reluctantly. The same attitude should also be applied to pruning trees. Of course trees are not as important as people, but they happen to be the single most precious element in the garden. Pruning, even in the most skilled of professional hands will always cause at least some damage, but irrespective of the skill or otherwise of the gardener, the time of year is also a major factor to be considered. The issue is less problematical for gardeners in cold winter climates, because the guidelines are pretty clear. Deciduous plants are pruned during their dormant season, namely the winter, while broadleaf evergreens are not touched until the spring. Furthermore, the range of plants is naturally restricted to those hardy to freezing temperatures.

In Mediterranean climates though, typified by hot dry summers and mild wet winters, plants originating from tropical and sub tropical regions are commonly seen in gardens, together with plants from cold and temperate areas. To add a further complication, even places that incur light frosts, can also experience dry warm spells, where the temperatures often rise to the 20c mark and beyond, to be followed by further cold snaps and frosts. These weather patterns have implications in fact not only for cold sensitive species, but for the hardy ones as well.

Any plant, whether tree, bush, or herbaceous, should not be pruned in any manner if it is sensitive to cold, until all possibility of frosts have passed. On the other hand, naturally deciduous plants, that is those that drop their leaves in the autumn as a dictate from their genetic code, should be pruned in their dormant season, as in cold winter climates. The important difference to be remembered however is that in cold winter places, pruning is usually carried out at the beginning of winter, whereas pruning cuts in mild climates at this time can actually be detrimental to the tree. Why is this the case? The combination of sufficient moisture, (this is the wet season) warm spells, and pruning, are conducive to renewed plant growth.

It is this juvenile growth which is liable to be adversely affected by a frost that may follow a prolonged warm spell. The damage incurred by young, fleshy tissue is both direct and indirect. Directly, the damaged parts provide excellent conditions for fungal and bacterial infections to develop. Indirectly, the tree has simply wasted energy in growing new tissue only for it to be destroyed. Most people are unaware of the significance of positive energy levels being maintained in the tree but in the view of many arboriculturists, this the key to healthy tree growth and development.

The conclusion to be drawn is that hardy trees should be pruned right at the end of the dormant winter season. Where I live, (central Israel) we prune plants in this category from about the middle of February, because by the time new growth does appear, (the growth being partially induced by the pruning) about six weeks after pruning, the possibility of frosts has passed. That which applies to trees holds good for shrubs and bushes, including roses as well. From my experience, herbaceous perennials can be safely cut back at the beginning of the winter, providing that your winter climate is mild, and that the plants are not especially tender.