Perfect pruning result can be all in the timing

The silver birch needs pruning. Picture by Tom Pattinson.
The silver birch needs pruning. Picture by Tom Pattinson.

Pruning in one form or another is a gardening activity that continues throughout the year.

Some plants can be reduced in size, width or density without consequence, others may object mildly or strongly, even expire, after being pruned too severely or at the wrong time.

A reminder of this came last week with a silver birch (Betula pendula), which in keeping with most other deciduous trees and shrubs, has been dormant since leaf-fall last autumn and therefore receptive to the biennial trim that keeps growth within bounds.

But there is no specific calendar date to inform us when dormancy ends, that’s all down to weather. All we can do is look for pointers – growth buds enlarging, embryo flowers or catkins appearing, etc.

December to January would have been ideal, but here we were on the threshold of March with a tree too tall for comfort, given the proximity of our greenhouse.

Action began from the tip outwards, Andrew, the professional, pruning with an eye to reducing the height whilst maintaining shape. As we walked around at ground level to review the result, there was one branch, circa 7cm diameter, spoiling the chi. It had to go, and predictably, the sap flowed like a dripping tap.

In such circumstances, it’s best leaving it all to nature. Several hours later the wound was dry and clean, no lasting harm done, and we are set for a pendulous display of flowering catkins.

There was a similar experience with the old grape vine a few years ago when gale-force winter winds wrecked the greenhouse. The collapsed structure damaged a main rod and part had to be removed by saw, before it was wrapped in fleece and bubble film to protect it from the elements. The sap flowed for a whole day – so much for dormancy. But the vine survived and is ready for another year of fruiting.

Timing of the annual prune for any woody perennial, be it light or severe, can make the difference between success or failure.

Ornamental shrubs, such as buddleja, lavatera, weigela, fuchsia and potentilla, all flower on new growths so if you reduced their height even at this late stage, they would still offer bloom.

It follows that any due to flower before the end of May, for example forsythia and winter heathers, should have been pruned immediately after blooming last year. This encourages new growths to develop and ripen over the summer period.

Other significant best pruning times include May for broad-leaved evergreens, late summer for flowering cherries, and autumn for conifers.