Chop, chop, it’s pruning time

To a non-gardener, the idea of cutting back a growing plant as a way of encouraging it to grow, seems, quite understandably, like an inexplicably odd and entirely counter-productive thing to do. And yet for various reasons, many plants benefit from a regular prune, in much the same way that we humans benefit from regular visits to a dentist or a hairdresser.

Sometimes it’s done in order to remove dead, damaged, weak or crowded branches, and thus keep the plant in good shape. With large, established trees and shrubs, this kind of pruning can also be a means of addressing possible health and safety concerns as regards falling branches or potentially hazardous dead wood.

Gardeners also prune plants as an effective means of preventing the spread of disease, for example, cutting out the diseased branches of an apple tree that shows signs of the common fungal disease known as canker to prevent it from eventually killing the tree, or cutting away rose foliage infected with black spot to ensure a good display of flowers.

In this case, pruning acts as a form of plant hygiene, where the aim is to remove the diseased plant material and then quickly and careful dispose of the prunings by burning or binning them (but not in the compost bin). Remember, too, to disinfect your tools both before and after completing the job.

Health and safety aside, pruning can also be a wonderful way of artfully shaping and sculpting a tree or shrub, in which case the judicious removal of branches can have the result of transforming the ugliest of ducklings into a swan.

But I should add the proviso that this is only if the secateurs or pruning saw is in the right pair of hands. Sometimes it isn’t, and the unlovely result isn’t so much sculptural as sepulchral. There’s no more melancholic sight than a tree shorn of all its branches so that it resembles a telegraph pole, or a once-graceful shrub pruned so hard that the result is unavoidably reminiscent of some unfortunate animal’s skeletal remains. So take a gently, gently approach, and try not to let yourself (and your secateurs) get carried away in a burst of enthusiasm.

Aesthetic reasons aside, gardeners routinely prune many different plants in order to encourage the production of an abundance of fresh, healthy growth. This sort of pruning is a clever way of manipulating the plant’s biochemistry by removing the growing tips of its branches – properly known as its apical buds – where the plant’s growth hormones are most concentrated and most dominant, and which inhibit the growth of other dormant buds lower down the branch.

Apical dominance, as it’s known, is a useful tool for survival if you are a plant that’s competing for available light, but as experienced gardeners will know, it doesn’t always result in a beautifully proportioned, floriferous or productive specimen. For example, it can make for a tall and straggly specimen of climbing clematis, where the flowers are high up and far out of sight. Or it can result in an apple tree where what little fruit there is is far out of reach. And so, when required, we gardeners do what we can to outwit it.

While recommended pruning times and techniques vary greatly according to the particular plant (if in doubt, always consult a reference book or the RHS website before you cut), late winter/early spring is one of those times when I keep my battered, scarlet-handled secateurs close at hand.

First to go are the faded stems, flower heads and old leaves of many perennials, including those of hellebores, epimediums, Verbena bonariensis, Achillea, Aconitum, Eryngium, Japanese anemones, Sedum, and Crocosmia, as well as fennel, marjoram and winter savory. The same goes for the faded canes of autumn-fruiting raspberries, while now is my last chance to winter-prune apple trees as well as gooseberry and currant bushes.

Other plants that feel the secateurs’ sharp blades at this time of year are any of the late-flowering clematis (properly known as pruning Group 3), all of which flower on this season’s new growth. In their case, I make sure to prune back to just above the plant’s first pair of strong, healthy buds.

Now’s also the time, if required, to prune some of the winter-flowering shrubs that have finished their seasonal floral display, including the richly-scented winter honeysuckles (Lonicera sp), Viburnum x bodnantense and V. farreri and winter jasmine, as well as the winter dogwoods grown for their colourful stems.

Many late summer-flowering shrubs can also be pruned this month, including the butterfly bush Buddleja davidii, Caryopteris, Perovskia, Romneya, Potentilla, Fuchsia, and the deciduous, blue-flowering Ceanothus ‘Gloire de Versailles’, all of which flower on new growth.

Many different types of roses can be pruned now too, as well as ornamental grasses, including Miscanthus, Calamagrostis ‘Karl Foerster’, Deschampsia cespitosa and Stipa gigantea.