Gardening is easy, we are assured. A bit of hard work, an eye for shape and colour, inspiration from other gardens, some good plants, and we can all do it. Nothing can get in the way of us creating our own private Eden.
If only it were that simple. While we may not need help in styling our garden, the nuts and bolts of how we achieve our ideal can be more complex. And there are no nuts or bolts more likely to derail a gardener’s best-laid plans than the hows, wheres and whens of pruning.
It can sometimes feel that you need years of study at Wisley or Kew before you even lift a pair of secateurs. The mountain of information about pruning can feel so daunting that nothing ever gets pruned. This, though, is not necessarily a bad thing: more damage can be done to shrubs and trees by pruning them badly than by leaving well alone. But pruning correctly can have a dramatic impact on the beauty and health of a plant. Fearful gardeners often take refuge in stories one hears about there being no difference between randomly pruning with the brute force of hedge trimmers and pruning slowly and carefully in the correct way. This may be true for a few plants, but in order for the vast majority to thrive they must be pruned correctly.
The first step in overcoming our fear of pruning is to understand why a particular tree or shrub needs to be pruned. One reason is simply to control the size and shape of a plant: simple hedges and extravagant topiary all need regular tidying. Another reason is to remove damage caused by weather or disease.. But the most common reason to prune is to increase the flower and fruit production of trees, shrubs and even perennials.
It is this is that seems complicated and leads to most anxiety: some plants flower on this year’s growth, others on old wood, some plants flower early in the year, others much later. All need different pruning regimes. But don’t be put of. Begin by learning about the plants that you actually grow. You don’t need to know how to prune Edgeworthia if the only shrubs in your garden are Buddleia. Remember, though, that not all species of the same genus are pruned in the same way.
The correct time of year to prune varies from plant to plant. Pruning at the wrong time will not kill a plant, although continually doing so might weaken or damage it. In general, the worst time to prune is immediately after new shoots appear in early spring. Removing new shoots limits the amount of energy a plant can generate to produce more growth. Avoid, also, removing shoots in early autumn, as this may encourage new shoots that will be unable to withstand winter weather. These are principles, not rules. Sometimes pruning at the ‘wrong’ time is unavoidable. If a shrub becomes damaged by wind, by the dogs chasing pigeons, or by an inattentive builder, it is best to prune out the damaged stems immediately.
It is easy to get carried away when pruning and to end up cutting away far more than is necessary. Cutting back a plant often has a dramatic effect and this can generate an enthusiasm that is hard to control. Women gardeners assure me that this is a chap’s problem: we think that we are hacking through a jungle when in fact we are just thinning out the fig tree. I have certainly been guilty of this myself, pruning the cherry tree and thinning the cob nuts to a point where fewer cherries and hardly any cob nuts appeared the following year. If you begin to feel an adrenalin rush when pruning it is probably time to stand back and reflect on whether what you are doing is really necessary. Either that or ask a woman to help with the pruning.
Over the next few months we will be looking at how and when to prune particular groups of plants and at the effect that correct pruning has on them. The articles won’t lead to an ‘A’ Level in pruning, but they should not only help overcome any fears you may have but also give you healthy and beautiful plants.
A bit of botany
Understanding how plants grow and develop, and the effects on plants of cutting into a stem, is important for successful pruning. Many gardeners have an aversion to the science of plant growth but, when it comes to where and how to prune, a little bit of botany goes a long way.
The buds at the tip of tree and shrub stems – the apical buds – produce growth-restricting hormones (known as auxins) that are sent back through the stem to buds lower down. Auxins inhibit the development of these buds into further stems that would overcrowd and compete with the dominant apical bud. Removing this stem allows the lower set of buds to form into stems. These new stems will, in turn, produce auxins to inhibit the lower buds.
It is easy to understand this process when you consider a yew hedge. Anyone who has planted a yew, or any other hedge, knows that, until the hedge reaches the height you want, it is thin and straggly. The moment you cut the leading stems the rest of the hedge begins to sprout new shoots and will quickly thicken out. The yew is trying to grow into a large tree, but the constant clipping prevents it from forming a trunk, and encourages shoots to form lower down the hedge. These principles are the same for all trees and shrubs that are pruned.
For all shrubs that have individual stems pruned the cut is the same. Make a clean cut just above a bud, at an angle sloping away from it. A snag from blunt secateurs, or too long a piece of stem left above the bud, will rot and allow disease to get into the rest of the healthy stem. Rot will also be caused by a flat cut, or one angled towards the bud, which will channel rain towards it.