Why prune

Pruning Basics

The Three D's (dead, diseased and dying)
You should always prune out any dead diseased or dying parts of the plant. It is important remove these to help maintain the plant's overall health. Dead growth can lead to further death or disease and uhealthy growth may also cause further related issues.

Also remove inward growing stems that can cause congestion issues, such as rubbing or bruising or encouraging diseases which result from crowding in the plant.

Used or unwanted growth
Spent growth, such as flower stalks left after the flowers or fruit have fallen, may still be using plant energy. Removing these will help the plant better use its limited energy resources.

Unwanted growth also uses the plant's energy. These include 'suckers' or shoots that appear from the roots around the parent plant, or shoots that grow from the base of grafted plants (where the roots of one plant have been joined to the stem of another plant). Left unchecked this unwanted growth can be much more vigourous than the parent plant and may eventually out-compete it eventually killing it off.

Reverted or unusual growth
Reverted growth can be particular problem for cultivars with variegated or coloured leaves. This is a process in which parts of the plant lose their bred features and 'revert' back true to the original species. These reverted stems are best followed back to their source at the base of the plant and removed.

Growth that looks unlike the rest of the plant is known as not 'true to type'. Contorted growth and even different flower colours can be found growing in otherwise normal plants, due to damage or natural variation in growth. These can also be traced back to their source and removed, or you can leave them alone. New cultivars of plants can be found this way.

Saving space, safety and good practice
If a plant is starting to out-grow its space prune it back. Keep paths and gateways, driveways, windows and doors clear. If your garden is on a public footpath or pavement, you will be required to keep your plants from growing over and blocking it. Further advice on keeping public rights-of-way clear can be obtained from your local council at www.open.gov.uk

High hedges (especially fast growing conifer species like Leylandii) can illegally block out views and daylight from your neighbours. To ensure you are not breaching their rights go to www.odpm.gov.uk for more details.

Pruning for effect This second section reviews techniques to encourage your plants to grow in the way you want them to.

Pruning to establish plants
To quickly establish vigourous, branching plants (e.g. new hedges) prune away the tips of stems to encourage shorter, bushier growth. As the leading shoot is dominant over the other shoots below it, removing the leading shoot then allows the other shoots to grow to their full potential.

Decorative pruning

Puning to promote flowers and fruit
Many plants benefit from pruning, inlcuding roses, wisterias or fruit trees. The basic principle is the same: Limit the amount of leaf and shoot growth (vegetative growth) and increase the amount of flowering and fruiting growth (reproductive growth).

This type of pruning is often carried out annually and will be combined with selecting and training branches to improve yields. The branch angle also plays an important role in producing reproductive wood. The general rule is vertical growth produces vegetative growth, and horizontal growth produces reproductive growth. Systems of ornamental training that use these rules include cordon, espalier and fan training of wall fruit.

Pruning and training for shade
By training the upper branches of trees (e.g. Plantanus and Tilia) to grow horizontally, and pruning out any upwardly growing branches, you can create a larger shaded area as a retreat from the hot summer sun.

Rejuvenating plants and prolonging their life
By hard pruning mature plants, you can encourage fresh, young re-growth. Often regular pruning will keep young, healthy, vigourous growth and increase the life-span of the plant. Some plants (e.g. lavender) cannot, however, produce new growth from older, tougher wood. A good indicator of this type of pruning working, is with plants where new shoots are constantly being produced from its base and over the older thicker stems.

Coppicing for stem colour and leaves
Some shrubs which are grown for their colourful stems or interesting foliage will benefit from an annual hard-prune. This type of pruning is known as coppicing.

When not to prune

Plants intolerant of pruning
There are some plants (e.g walnut trees and some larger leafed magnolias) that simply don't like being pruned. Every time you prune, you're creating wounds on the plant. In extreme cases this can lead to the plant 'bleeding' to death, as it may not be able to stop sap flowing out the its wounds. This can be minimised by pruning at the right time of year when sap flow is naturally lower.

Making plants vulnerable to pests and diseases
From the moment you've pruned, until the wound has fully healed, plants are more vulnerable to pests and disease. This too can be minimised by pruning at the right time of year, when the risks are lower.

Natural habit
Pruning and training sometime ruins the natural plant habit. 'Specimens plants' (e.g. Edgeworthia chrysantha and Japanese Maples) have strong, beautiful natural habit and should be left as they are.

Too formal
Pruned trees and shrubs often don't work well in informal, natural or wild gardens.

Privacy & exposure
Allow shrubs to grow to give privacy, a break from the wind or protection from surrounding noises.

Habitats for wildlife
Don't forget the wildlife that lives in your garden. Make certain you are not pruning hedges when birds are nesting. Also allowing herbaceous perennials to overwinter, allows small wildlife to hide and overwinter too. Piles of dead wood, especially from native plant species, makes a well-needed home a variety of creatures and fungi, which in turn supports an entire food-chain in your garden.

Tree Preservation Orders and trees in conservation areas
You may need to have any planned work approved by your local authority first. If in doubt, it's better to check with your local authority's Tree Officer. To find your local authority's website, check out www.open.gov.uk