What is crown reduction, and is topping a tree bad?

Knowing these four terms changes the conversation with a contractor completely, because 'can you cut that tree back a bit' is exactly the request that produces a topped tree. Specifying crown reduction by a stated amount, or crown lifting to a stated height, gets a professional result, and a contractor who is happy to top a tree has told you something useful about them.

Step by step

1. Crown reduction: shortening the whole crown proportionately.Each branch is cut back to a suitable smaller side branch that can take over as the new leader for that limb. The tree keeps a natural outline, just smaller. Specified as a reduction of a stated distance or percentage — 'reduce the crown by two metres' — not as 'take it down to that height'.
2. Crown thinning: removing selected branches throughout.Taking out a proportion of the secondary branches evenly through the crown to let more light and wind through, without changing the tree's size or shape. Usually specified as a percentage, and rarely more than about 20 to 30 per cent, because more than that stresses the tree and stimulates dense regrowth.
3. Crown lifting: removing the lowest branches.Raising the clearance beneath the tree over a path, a lawn or a road, specified as a height above ground. Often the most effective way of getting light into a garden, because it lets low morning and evening sun under the canopy, and it is much less stressful to the tree than reduction.
4. Pollarding: a system, not a one-off cut.Pollarding cuts a tree back to the same points repeatedly from a young age, producing the characteristic knuckled heads seen on urban limes and willows. It only works as a continued cycle, started early, and cutting an old unpollarded tree back to stumps is not pollarding — it is topping.
5. Understand why topping is bad.Cutting through large-diameter wood at an arbitrary height leaves wounds the tree cannot seal, so decay enters the exposed stubs. The tree responds with a mass of vigorous shoots that grow from buds just below the cut, attached only to the outer wood rather than properly anchored. Those shoots grow fast, get heavy, and are attached to a decaying stub. Ten years on you have a taller, weaker, more hazardous tree that needs the work doing again.
6. Recognise that topping does not solve the problem it was meant to.A topped tree regrows faster than an unpruned one, because the roots are unaffected and the tree is racing to replace lost leaf area. Within a few years it is back to its previous height with worse structure.
7. Ask for the right thing when you get quotes.Say what you want to achieve — more light to that window, clearance over the drive, less wind loading — and let the arboriculturist specify the work. Reputable contractors work to recognised British Standard specifications for tree work, and quoting in those terms is a good sign.
8. Keep reductions modest.As a general guide, no more than about a fifth to a quarter of the live crown in one operation, and less on old, stressed or slow-growing trees. Reduction is better done in stages over several years than in one severe cut.
9. Check for protections before commissioning anything.TPOs cover pruning and topping, and Conservation Areas require notice. Councils frequently refuse consent for topping specifically because it is poor arboricultural practice, and they will often approve a sensible reduction instead.
10. Consider whether the tree is simply in the wrong place.A forest species in a small garden will need reducing every few years forever. Removing it and replanting something of appropriate size is sometimes the honest answer, and costs less over twenty years.

Tips

• Crown lifting is under-used. In a small garden it often achieves more usable light than reduction and is far kinder to the tree.
• A quote that says 'cut back' with no specification is a warning sign. Ask what will be removed and to where.
• Photograph the tree before and after. It is useful for the next contractor, for insurance, and for judging whether you got what you paid for.

Common mistakes

• Asking for a tree to be 'taken down to the fence height' — That is a description of topping. Ask for a reduction of a stated amount instead, and let the arboriculturist find suitable cut points.
• Accepting the cheapest quote for crown work — Topping is quick and requires no skill, which is exactly why it is cheap. Proper reduction takes longer and costs more because it is a skilled job done one branch at a time.
• Reducing a tree hard to solve a light problem — It grows back faster and denser. Crown lifting or thinning often solves the light problem more durably, and sometimes the honest answer is that the tree is too big for the site.
• Topping a conifer to reduce its height — Most conifers other than yew do not regenerate from old wood at all, so the cut top stays a flat dead surface permanently.

Questions people ask