Regular pruning of certain trees and shrubs can increase vigour, improve fruit or flower production, and ward off disease. But it can be difficult to remember the techniques required to do a good job, and it’s hard to know if you’re doing it right.
There’s no one, catch-all way to prune all plants. You’ll need to prune at different times of year and in different ways, depending on what plants you’re growing, how you’re growing them, and what you what from them. It’s therefore important to research how to prune each plant before you set about pruning it. Pruning at the wrong time of year, or in the wrong way, can lead to all sorts of problems, not least the plant putting on lots of extra leafy growth at the expense of fruit or flowers.
Avoid making them and you’ll be rewarded with better looking, healthier plants.
Pruning at the wrong time of year
Pruning cut dripping sap
Most plants are pruned in winter, when dormant, but there are exceptions. Cherry and plum trees, for example, are susceptible to silver leaf disease, and should therefore be pruned in summer when the risk of infection is reduced. Likewise, most spring-flowering shrubs should be pruned immediately after flowering. Grapevines, pictured, should be pruned only in December and January, otherwise you may cause the plant to bleed sap, which weakens the plant and can eventually kill it. By conducting a little research before you stat pruning, you can avoid anything from removing the shrub’s flower buds, disease and potential death of your plant.
Pruning too much
Pruning removes stems and leaves, which are two main sources of food for the plant – carbohydrates are stored in wood, while leaves produce their own carbohydrates when they photosynthesise. Removing too much material at once can result in die back of the roots and it may take several years for the tree to recover. What’s more, if you prune out the leader (known as ‘topping’), the plant can go into shock and put on lots of leafy growth at the expense of flowers and fruit. So, unless you’ve been directed to conduct a ‘hard prune’, make sure you prune less, more regularly.
Not pruning above a node
Pruning a hydrangea stem
The node is where leaves, buds and shoots emerge from the stem. You should always cut just above a node, as this prevents ‘die back‘ and therefore disease. Also, by cutting above a node you can manipulate new stems, leaves or flowers to form in a desired direction, as nodes form on different sides of a stem. Don’t cut too closely above a node as this can damage it, but avoid leaving more than 1cm above the node as you will leave an unsightly stump, which can’t grow and may therefore die.
Not cleaning secateurs
Clean, sharp and well-oiled pruning tools function better, last longer and are safer to use than those which are dirty and blunt.
If you don’t sharpen your secateurs and loppers then you’re less likely to make a clean cut when pruning. A messy cut will take longer to heal than a clean cut, and could therefore let disease enter the plant. If you don’t clean and disinfect your tools after using them then you could unwittingly spread disease, such as canker, between plants.
Not pruning at an angle
Pruning weigela using loppers
When pruning branches it’s important to cut at a downwards angle, so that when it rains water runs quickly off the wound. But cutting flat you run the risk of fungal infections entering the plant, as water can pool on the wound and create the perfect conditions for fungi to take hold.
Not pruning out canker
Canker on an apple tree branch
Canker is an airborne bacterial infection that infects trees in the Prunus genus, via damaged wood. By pruning out early signs of canker you can prolong the life and vigour of the tree, but by ignoring it you run the risk of shortening the tree’s life expectancy.
Not removing die-back
There are several causes of die back, including bad planting, bad pruning (see above), frost damage and physical damage (for example when branches rub together). Sometimes, fungi can invade these dead shoots and cause canker, which spreads to other parts of the plant, potentially weakening it. It’s therefore important to prune out die-back is therefore important to prevent disease.