As professional arborists and tree surgeons, the Tree Surgeon Pro team is often asked about tree pruning. Customers ask questions such as, Is it necessary? Will it harm the tree? What's the best method? And so on. But one of the most frequently asked questions is, When is the best time to prune trees?
We started our tree care blog series to offer helpful advice to all who need it, and one of our posts deals with the latter question in full, so you know when it's the right time to prune trees. Alternatively, you need to know when to avoid pruning, so we decided to address that with a special blog on this subject.
Sadly, many people don't realise that the timing is crucial - get it wrong and you could damage your trees permanently, or even lose them!
So, to help you avoid this scenario, here's our advice...
While it might seem counterproductive to cut off bits of your tree, it can have several benefits - but only if proper pruning techniques are used and it's done at the right time!
Here are some of the reasons why pruning is necessary:
It's all very well knowing this, but why does it have to be done at certain times of the year? Why can't you lop off those annoying branches when you have the time and energy to do so?
The truth is that, depending on the tree species, as well as its age - you can do a great deal of harm.
Pruning isn’t just about tidying up branches. It’s a bit like surgery for your tree - a careful balancing act between aesthetics, safety, and the tree’s health. Tree topping vs pruning is an important distinction here; while pruning is a precise method that promotes healthy growth, tree topping is a more aggressive approach that can weaken the tree and lead to structural issues. Done at the wrong time, pruning can leave your tree vulnerable to diseases, pests, and stress. In the worst cases, you can even kill it.
The UK’s climate, with its defined seasons and sometimes temperamental weather, adds an extra layer of complexity. That’s why choosing the right moment is critical! The secret is to carry out this essential task during the dormant season, when the sap isn't flowing fast and the tree's growth has slowed down (You can discover more about this in our other blog about the best time to prune trees, as mentioned above).
This generally affects deciduous trees more than it does evergreen trees, so we'll check these out first...
Generally speaking, When is the worst time to prune trees in the UK? The absolute worst time to prune deciduous trees is between late spring and early summer (May to July, in effect), and here's why:
During late spring and early summer, trees are actively growing. Leaves are unfurling, branches are stretching, and the tree is pouring all its energy into photosynthesis to fuel this surge of development. It’s like the tree’s equivalent of a growth spurt, where every ounce of energy is directed toward strengthening and expanding its structure.
Pruning at this stage can throw a spanner in the works. By cutting back branches during this critical period, you’re not just removing excess growth, you’re disrupting the tree’s natural rhythm.
This sudden interruption forces the tree to divert energy toward healing and sealing the pruning wounds instead of continuing its growth. Leaves are food factories, so removing these affects the tree's ability to create and store enough food. As a result, the tree can become stressed, weakening its overall health and leaving it vulnerable to pests, disease, and even stunted growth in the following seasons.
In some cases, severe or poorly timed pruning during this period can have long-lasting consequences, preventing the tree from reaching its full potential. That’s why it’s best to resist the urge to prune when your tree is at its busiest!
For certain species like maple, walnut and birch trees, pruning in early winter through to spring can cause excessive sap loss, known as bleeding. While this isn’t always fatal for a tree to bleed sap from pruning wounds, it’s certainly not ideal and can weaken the tree considerably.
Fresh pruning cuts on a tree are a bit like open wounds on human skin, vulnerable and exposed. In late spring and early summer, when the weather is warm and humidity levels rise, these fresh cuts become a magnet for pests and fungal spores looking for an easy entry point. The combination of warmth and moisture creates the perfect breeding ground for infections to take hold.
One of the biggest threats during this time is canker, a fungal disease that can penetrate through wounds and damaged wood, where it will slowly spread, causing serious long-term damage. If left unchecked, canker can weaken branches, cause dieback, and in extreme cases, lead to the gradual decline of the tree. What starts as a small wound can quickly escalate into a major problem that’s difficult - and sometimes impossible - to reverse.
Although not associated with tree health, this aspect is just as important: Early spring to late summer (February to August is the official nesting period, according to Natural England) are peak nesting times for birds and other wildlife. If you prune a tree during this period, you might accidentally destroy nests or disrupt breeding cycles. In the UK, disturbing nesting birds is a violation of the Wildlife and Countryside Act 1981, potentially resulting in a six-month prison sentence and an unlimited fine!
Older trees require less pruning, on the whole. They don't respond well to drastic cuts, so a gentler approach is needed. As a rough guide, never remove more than 10-15% of the canopy, or you may put the tree under severe stress that could endanger its life.
While pruning in late autumn/mid-winter/late winter is generally best for many trees, specific tree species may differ as to the best or worst time for pruning! However, it's best to avoid pruning them in spring and summer.
Timing is everything here. While a well-timed prune promotes healthy growth and better fruit yields, cutting at the wrong time can stress the tree, reduce fruit production, and even invite disease. Here’s when not to prune and why:
For stone fruits like peach, cherry and plum trees, the absolute worst time to prune is during the dormant winter months (November to March). Pruning during this period exposes the tree to silver leaf disease, a fungal infection that enters through pruning wounds and spreads through the tree’s vascular system. Silver leaf can cause branches to die back and, in severe cases, lead to the tree’s decline.
While apples and pears are generally pruned in winter, avoid pruning them during early spring (March to April) when the tree is just starting to come out of dormancy. At this stage, the tree is beginning to channel energy into new growth and fruit bud development. Pruning too early can divert this energy toward healing wounds instead, reducing the amount of energy available for producing fruit.
Pruning fruit trees when conditions are wet, damp, or frosty should be avoided at all costs. Wet weather creates the perfect environment for fungal spores to enter fresh cuts, increasing the risk of infections like canker and other diseases. Similarly, pruning during frosty weather can cause the exposed cuts to freeze, leading to dieback and damage.
Evergreens are a little different, as they don't lose their foliage in winter, so they don't experience a dormant season, as such. They just carry on the process of photosynthesis right the way through, but at a slower rate.
Even so, the very worst time to take the secateurs to your conifers is during late summer to early autumn, August and September in particular. Here's why this is not a good idea:
Pruning during late summer or early autumn can stimulate a burst of tender new growth just when the tree should be winding down for the colder months. These tender, fresh shoots may look healthy at first, but they’re highly vulnerable because they haven’t had time to mature and harden before the first frosts arrive. When temperatures drop, this soft, new growth is often the first to suffer, leading to dieback and damage that weakens the tree overall.
Even worse, if a severe frost hits early, these vulnerable shoots can become so damaged that they never recover properly, leaving bare patches that affect the tree’s shape and long-term health. This unnecessary stress can set the tree back and leave it more susceptible to diseases and pests over the coming seasons.
Some evergreens, particularly pines, are prone to excessive sap flow if exposed to summer pruning. When cuts are made during this period, the tree responds by producing large amounts of sticky resin to seal the wound. While this is a natural defence mechanism, losing too much sap can weaken the tree, draining its energy reserves and leaving it more vulnerable to pests, disease, and environmental stress.
Late-season cuts can leave evergreen trees highly vulnerable to fungal infections and pest infestations just as temperatures begin to cool and moisture levels rise. These conditions create the perfect environment for harmful, wound-related pathogens to thrive, making it easier for diseases to take hold.
Once a fungal infection sets in, it can spread quickly, weakening the tree and potentially causing long-term damage that’s difficult to reverse. Similarly, opportunistic pests are more likely to target stressed or weakened trees, putting the tree’s health at even greater risk.
At Tree Surgeon Pro, we understand that timing is everything when it comes to tree care. Whether you need expert advice or professional pruning services, our experienced team is here to help.
Get in touch today to keep your trees healthy and thriving year-round!
