Although different shrubs and trees may need different pruning techniques, the physical process of making the cuts is usually the same. Cuts are generally made with secateurs (pruners), or long-handled pruners for thicker growth, or a saw of some kind.
There are several general principles that apply when you are using all types of pruning equipment. The first may seem obvious, but it is often overlooked. The cut must be clean and there should be no tears in the wood or bits left hanging around the cut. The one essential requirement for achieving this, besides the ability to use the tools properly, is for the tools to be sharp and well maintained. A pair of secateurs that crushes the wood, rather than cleanly cutting through it, can cause problems.
When pruning trees, be aware that branches can be heavy, so avoid cutting straight through one in such a way that the weight makes it fall before you have finished cutting, tearing back along the branch or even down the trunk.
The second basic principle is to avoid snags. Snags are the short pieces of wood that stick out beyond a branch or a bud. All cuts should be made tight against the stem or up to a bud if removing the end of a shoot. Any piece of wood sticking out will not only look ugly but will usually die back, leaving dead wood through which diseases can enter.
On roses, for example, if you leave a snag when deadheading, the stem may die back not just to the next bud but further down the branch.
Incorrect and Correct Pruning Cuts
Incorrect Cut: Do not make the cut too close to a bud. Aim to make the cut about a quarter of an inch above a bud.
Incorrect Cut: Do not cut too far above a bud, leaf or shoot because the remaining stub is likely to cause die-back.
Incorrect Cut: Do not slope the cut towards the bud as this is likely to cause rotting if water drains into it.
Incorrect Cut: All pruning cuts should be clean, with no bruising or ragged edges because these will allow disease to enter.
Correct Cut: The ideal cut is one that slants away, just above the bud. This will shed the rain away from the bud.
Correct Cut: When a pair of buds in involved, cut straight across the stem, just above the buds, without damaging either.
Ends of shoots or branches
When you are removing the end of a shoot or a branch, a sloping cut should be made just above the nearest bud to the point at which you want to shorten the shoot.
The cut should be sloped at 45 degrees away from the bud (be careful not to cut through the bud). If you do accidentally cut through the bud, it may be necessary to recut back to the next bud. If there are two buds opposite one another, make the cut directly across the stem just above the pair of buds.
Removing a branch or stem
Always cut off a branch or heavier stem with three cuts. This will help prevent the branch splitting. The first cut is made some way out (about 30cm/12in or so) from the trunk, in an upward direction, about a third of the way through. The second is made 8cm (3in) further along the branch and in a downward direction. As you pass the initial cut the branch will sag and split along to the second cut but will go no further. You can now cut straight through the remaining stub, close to the trunk.
Argument has raged for many years as to whether larger cuts should be sealed with some form of compound. Although some gardeners still stick to the practice, most now feel it is best to leave all cuts open to the air and weather. Trim round the cut with a sharp knife to remove any rough bark.