Pruning a tree properly
Cut in the right place, at the right time, and know the point where the job stops being yours.
Cut at the collar, not flush
A branch meets the trunk at a slightly swollen ring called the branch collar, and that collar contains the tissue the tree uses to seal the wound. Cut outside it and the tree closes the wound over a season or two. Cut flush to the trunk and you remove the collar, so the wound never seals properly and decay enters the trunk.
Leaving a long stub is the opposite error and almost as bad: the stub dies back and rots, and the decay travels inward. The cut goes just outside the collar, angled to follow it.
- Just outside the collar
- The swollen ring at the base of the branch. It holds the tissue that seals the wound.
- Never flush to the trunk
- It removes the collar, the wound cannot seal, and decay gets into the trunk itself.
- Never leave a stub
- It dies back and rots inward. Both errors are permanent and both are avoidable.
- No wound paint
- It seals moisture in rather than out. A correct cut left alone heals better than a painted one.
Three cuts on anything heavy
A branch heavy enough to tear will strip bark down the trunk as it goes, and that wound is far larger than the cut you intended. The three cut method prevents it: an undercut a short way out from the collar, a top cut slightly further out that drops the weight, then the final cut at the collar with no weight on it.
The first cut is the one people skip, and it is the one that stops the tear. Once the weight is off, the final cut is small and controlled.
- Undercut first
- A third of the way through from below, out from the collar. This is what stops the bark tearing.
- Top cut further out
- Slightly beyond the undercut. The branch drops cleanly at the undercut rather than peeling.
- Final cut at the collar
- With no weight on it, so it is small, accurate and controlled.
- Anything over about 25mm
- Use three cuts. The weight it takes to tear bark is less than most people expect.
When to prune, and when not to
Most deciduous trees are pruned in late winter while dormant, when the structure is visible and there is no leaf to work around. Some are exceptions with real consequences: prunus, meaning cherries and plums, must be pruned in summer because winter cuts invite silver leaf disease.
In the UK it is an offence to damage an active bird nest, so between roughly March and August any cutting needs checking first. Trees can also be protected individually or by a conservation area, and cutting one without consent is a prosecutable offence with substantial fines.
- Late winter for most
- Dormant, structure visible, no leaf in the way. The default for deciduous trees.
- Summer for cherries and plums
- Winter cuts on prunus invite silver leaf. This exception matters and catches people out.
- Check for nests, March to August
- It is an offence to damage an active nest. A look before cutting takes a minute.
- Check for a TPO
- Tree Preservation Orders and conservation areas. Cutting without consent is prosecutable, and the council will tell you free.
Working at height, and the wrong ways to do it
A pole saw from the ground handles most domestic pruning up to about five metres, and it is the safe option because you are standing on the ground. The two things it demands are a hard hat, since everything you cut falls toward you, and awareness of where the branch will actually go.
The wrong ways are a chainsaw up a ladder, which is how people are seriously injured, and cutting above head height with anything you cannot control the fall of. A ladder is not a working platform, and a chainsaw needs both hands and a stable stance.
- Pole saw from the ground
- Up to about five metres. Safe because you are standing on it, and a hard hat is not optional.
- Never a chainsaw up a ladder
- It needs both hands and a stable stance. This is one of the most common causes of serious injury in tree work.
- Plan the fall
- Look up, then look at where you are standing. A cut branch swings and rolls rather than dropping straight.
- Nothing near power lines
- Not with a pole, not with anything. Contact does not require touching, and it is fatal.
When to call an arborist
Anything requiring you to leave the ground, anything near a power line, anything over about 100mm on a limb you cannot control the fall of, and any felling. Also anything on a protected tree, and anything where the tree is already damaged or leaning, because those behave unpredictably when cut.
This is not caution for its own sake. Tree work causes a disproportionate share of serious injuries among people doing it occasionally, because the loads are heavy, they move once cut, and the consequences of a misjudgement are immediate.
- Off the ground
- Climbing or a platform means a trained arborist with the right rigging and insurance.
- Near power lines
- Always the network operator or a qualified contractor. Never a domestic job at any height.
- Felling anything of size
- A tree falls where its lean and its weight decide, not where you intend, unless it is rigged.
- Damaged or leaning trees
- Stored tension behaves unpredictably when released. This is specialist work.
- Check insurance
- Any contractor should carry public liability. Ask to see it, since damage to a neighbour's property is the usual claim.
Frequently asked questions
- What tools do I need to prune a tree?
- Secateurs for anything up to about 15mm, loppers to about 40mm, a curved pruning saw above that, and a pole saw or pole lopper for anything out of reach. Add a hard hat, gloves and eye protection, because everything you cut from below falls toward you.
- Where exactly should I cut a branch?
- Just outside the branch collar, the slightly swollen ring where the branch meets the trunk. That collar contains the tissue the tree uses to seal the wound. Cutting flush removes it so the wound never seals, and leaving a long stub lets it rot inward.
- What is the three cut method?
- An undercut a third of the way through from below, out from the collar. Then a top cut slightly further out, which drops the weight cleanly at the undercut. Then the final cut at the collar with no weight on it. The first cut is what stops the bark tearing down the trunk.
- When is the best time to prune trees?
- Late winter for most deciduous trees, while they are dormant and the structure is visible. Cherries and plums are an important exception and must be pruned in summer, because winter cuts on prunus invite silver leaf disease.
- Do I need permission to prune a tree?
- Possibly. A Tree Preservation Order or a conservation area both require consent, and cutting without it is a prosecutable offence with substantial fines. Your council will confirm free of charge. Between March and August also check for active bird nests, which are protected.
- Can I use a chainsaw up a ladder?
- No. A chainsaw needs both hands and a stable stance, and a ladder gives you neither. It is one of the most common causes of serious injury in tree work. If a cut cannot be reached from the ground with a pole saw, it is a job for a trained arborist.
- Should I paint a pruning wound?
- No. Wound paints and sealants trap moisture against the cut and slow the tree's own sealing process rather than helping it. A cut made correctly just outside the branch collar and then left alone heals faster and more reliably than a painted one.
- How thick a branch can loppers cut?
- Bypass loppers handle up to about 30mm, and geared or ratcheting versions up to about 50mm in soft wood. Beyond that a pruning saw is faster and puts less strain on you, and forcing loppers past their capacity springs the blades out of alignment permanently.
