Autumn is when most homeowners in Hertfordshire reach for the secateurs. The leaves are thinning, the garden looks untidy, and it feels like the right time to give everything a good cut back. But here is the problem: pruning the wrong tree at the wrong time can do far more harm than leaving it alone.
Not every tree responds well to autumn pruning. Some species are actively vulnerable to disease right now, and a well-meaning trim can open the door to infections that take years to show, and by then the damage is done.
So before you start cutting, here is what you actually need to know.
What You Can Safely Prune in Autumn
Some trees respond well to autumn attention, and a few actually prefer it.
Birch and Japanese maples are best pruned in autumn or early winter. These species have an early sap rise in spring, so pruning them later in winter or early spring causes heavy bleeding from the cut sites. Getting the work done now, while they are heading into dormancy, avoids that.
Dead, damaged, or diseased wood should be removed from any tree at any time of year. If a branch is clearly dead, cracked, or showing signs of decay, it is safer out of the tree than in it, regardless of the season. With storm season underway in Hertfordshire, removing deadwood now is a sensible precaution. A dead branch that holds through September might not survive the first November gale.
Light tidying work is generally fine on most established deciduous trees. Removing crossing branches, clearing growth away from paths or buildings, and taking out anything structurally weak are all reasonable autumn jobs, provided you are not removing more than about a third of the live canopy.
What You Should Leave Alone Until Summer
This is where most people get caught out.
Cherry, plum, and other stone fruit trees (including ornamental cherries, which are common across Hertfordshire gardens) should not be pruned between September and May. The reason is silver leaf disease, caused by the fungus Chondrostereum purpureum. Its spores are airborne and most active from September right through to late spring. Every pruning cut is an open wound, and in autumn those wounds heal slowly, giving the fungus an easy way in.
Silver leaf starts with a subtle silvery sheen on the leaves, which is easy to miss. By the time you notice it, the fungus is already inside the wood. It kills branches progressively, and in severe cases it kills the whole tree. The RHS recommends pruning these species only between April and July, when healing is fastest and spore counts are lowest.
Magnolias and walnuts are best pruned in mid-summer to early autumn. If you have missed that window, leave them until next year. Pruning them now risks excessive sap loss and poor wound closure.
Most conifers apart from yew will not regrow from old, bare wood, so any heavy pruning needs to be done carefully and within the growing season. Autumn cuts on conifers tend to brown off without recovering.
The One-Third Rule
Whatever you are pruning and whenever you are doing it, a safe guideline is never to remove more than a third of a tree’s live growth in a single year. Trees store energy in their branches and leaves, and removing too much at once forces them to use reserves they need to survive winter. Over-pruning in autumn is particularly risky because the tree has no growing season left to recover before the cold sets in.
If a tree needs significant reduction, it is usually better to spread the work over two or three years, or to have an arborist plan the cuts so the tree keeps enough canopy to sustain itself.
Do Not Forget the Legal Side
Before you prune anything in your garden, check whether the tree is protected by a Tree Preservation Order (TPO) or whether your property falls within a conservation area. In both cases, you need permission from your local council before carrying out any work, including pruning. Unauthorised work on a protected tree can result in fines of up to £20,000 in a magistrates’ court, or an unlimited fine in the Crown Court.
If you are unsure, your local planning authority can tell you. Or give us a ring and we will check for you.
When to Call a Professional
Light pruning from ground level is something most homeowners can handle safely. But there are clear lines you should not cross yourself:
- Any branch you cannot reach from the ground without a ladder
- Anything near overhead power lines or cables
- Large limbs that could fall unpredictably
- Trees that are leaning, have visible decay, or are close to buildings
- Any tree you suspect is protected
Chainsaw work at height is specialist work, full stop. It requires training, insurance, and the right equipment. It is never a DIY job.
If you have trees in your garden that need attention this autumn, we are happy to take a look and give you an honest assessment. Sometimes the best advice is to leave a tree alone for now, and we will tell you that if that is the case.
Call us on 01707 708202 or get in touch through our website for a free, no-obligation quote.
