Willow pruning in the summer

Do you have a willow tree in your yard that is growing fast and are thinking about pruning it in the summer? You’re not the only one. In the summer, we sit out in the garden and notice how quickly the willow sprouts. Branches can start to overhang, there’s a lot of shade on your lawn or patio, and maybe you’re worried that in a summer storm something will break off. Besides, you often have more time and desire to work in the garden in nice weather than on a cold winter day. But is it actually wise to prune a willow in the middle of summer? In this article we look at why people want to prune their willow in the summer, whether it’s a good idea, when it’s better to prune or not, what the consequences are for tree health and how to proceed safely. Finally, we will discuss alternatives if summer pruning turns out to be less than ideal. We keep it practical and approachable – just as if you were getting advice from a friendly arborist.

Why prune willows in the summer?

Many gardeners consider summer pruning for very understandable reasons. In the summer, a willow is in full leaf and growing the fastest. You may notice that by now the branches have become very long and are hanging toward the ground or touching the house. The tree can provide a lot of shade in places where you want sunlight, such as your flower bed or living room. Also, an unpruned willow can become top-heavy in the summer because of all the new shoots. You want to avoid branches tearing out or the tree becoming unbalanced. Besides, summer is the time for many people to tackle the garden – you have nice weather, long days and maybe vacation. It feels logical to grab the pruning shears or saw right then, so that the tree is back in neat shape and you immediately benefit from more light and space. And suppose you missed or postponed pruning in the winter, you soon think: can’t I still do it now? In short, convenience, timing and the visible growth of the tree are important reasons why people want to prune a willow especially in the summer.

Is summer pruning wise?

Then the big question: is it wise to prune a willow in the summer? Generally, the answer is no, rather not. While it is technically possible to prune a willow in the summer, it comes with a number of risks and disadvantages. This is because a willow is a tree with a very strong sap flow during the growing season. In spring and summer, the tree pumps plenty of sap (moisture with nutrients) from the roots to the branches to maintain and grow all those leaves. If you start pruning thick branches during this time, the tree may start “bleeding ” – a lot of sap flows out of the pruning wound. This sap loss weakens the tree and may even be so severe that the tree is damaged or (in extreme cases) dies. With willows, pruning in the spring or summer is known to create a high risk of bleeding to death.

In addition, in summer the tree desperately needs its leaves for photosynthesis (producing energy). If you prune away many branches in the summer, you deprive the willow of a lot of its “power plants” in one fell swoop. This can considerably weaken or shock the tree. You will notice that a heavily pruned willow may look limp and less vital in the summer. The tree will also try to compensate for the loss by quickly producing new shoots (called water locks). These grow wildly and are often weakly attached, which can cause problems later on.

Moreover, pruning wounds do not necessarily heal better in the hot, humid summer time – they provide an easy entry point for fungi, bacteria and insects. The combination of sap-rich wounds and high temperatures is ideal for wood rot fungi, for example, to strike. In winter, on the other hand, sap flow is minimal and pathogens are less active, allowing pruning wounds to dry out and close more peacefully.

In summary, summer pruning on willows is not wise in most cases. Unless it’s really necessary (for example, a dangerous branch about to fall), it’s better to wait to do any major pruning until the tree enters its dormancy period. This is safer for the tree and ultimately for you, because a healthy tree means less chance of accidents due to weakness or disease.

When is it better to prune or not?

The best time to prune a willow is in late fall and winter, roughly between late October and early March. During this period, the willow is hibernating: the leaves have fallen and the sap flow is almost at a standstill. If you prune during this dormant period, the tree hardly loses any sap and has plenty of time to form new buds on the pruned wood by spring. Also, in winter you can clearly see the shape and branch structure of the willow, which makes pruning easier. In the Netherlands, the traditional view is not for nothing that pollarded willows are pruned in winter by volunteers or farmers – that is the time when it makes sense. Willow branches are therefore often harvested in the winter (in the past, for example, for basket weaving) for exactly this reason.

When is it better not to prune? At least not in early spring. This is when the sap streams awaken again and the tree is about to sprout: pruning in March or April can cause the willow to bleed heavily. Also in mid-summer (around June, July) the tree is at the peak of its vigor, and pruning is not recommended. In addition, you must take into account the breeding season of birds: between about March 15 and July 15, many birds nest in trees and hedges. It is not forbidden to prune then, but if there is a nest in your willow and you would damage or disturb it, you are in violation of the Nature Protection Act. So from both a tree health and nature point of view, it is wise to leave the chainsaw and loppers for a while during that period, unless there really is no other way.

So are there times in the summer that are less unfavorable? If it is really necessary to prune in the growth period, preferably choose late summer. In August or early September, the tree begins to prepare somewhat for fall and the worst sap pressure is often over. Therefore, prune only small branches or light shoots, not the large, bearing branches. Also, a dry, cloudy day is better than a scorching hot day in July. But again: if at all possible, postpone pruning until after leaf fall.

A rule of thumb used by gardeners is not to remove more than 10-20% of the crown (leaf volume) at one time, especially during the growing season. If you do more, you unbalance the tree. So if you see a few small overhanging twigs that bother you, it’s best to remove them in the summer. But does the whole willow need major pruning back? Then wait for the right period (fall/winter), or hire an expert to do it in phases and responsibly.

Effects of summer pruning on tree health

What happens if, despite everything, you were to rigorously prune your willow in the summer? The consequences for tree health can be significant:

• Sap loss (bleeding): As mentioned earlier, a summer pruned willow will lose a lot of sap through the pruning wounds. This sap sometimes continues to drip for days. It costs the tree precious reserve nutrients and energy. Moreover, the sweet sap flow attracts insects (such as wasps and ants), which in turn can transmit fungi or diseases. In extreme cases, a tree can become so weakened by sap loss that parts of the branches or trunk die – hence the term bleeding to death.
• Poor wound healing: In warm conditions, pruning wounds stay “open” longer. The tree does try to close them with new tissue, but in the meantime, fungi and bacteria can infect the wound. Wood rot often develops this way. An improperly executed pruning (for example, ragged wound or cut too close to the trunk) heals even worse and can create a permanent weak spot in the tree. In winter, wounds tend to dry up faster and fungi have less chance, while in spring the tree grows smoothly over the cuts.
• Growth of water locks: When you remove many branches in the summer, a willow responds by quickly forming new shoots. These water locks often shoot straight up from the pruning wound or around the felled branch. They do grow quickly, but are less firmly attached to the tree. The result is a tangle of thin branches that easily break off again in the wind. Plus, it looks messy and you end up doing double duty in the winter to remove all those wild shoots again.
• Leaf loss and sunburn: A sudden pruning means that the tree suddenly lost a piece of foliage. That canopy also provided protection to the underlying branches and trunk from bright sunlight. After pruning in the summer, sun damage can occur on branches or trunk that have always been in shade and now suddenly come right into the sun. This can cause the bark to crack or scorch, which in turn can allow infections to enter. It also weakens the tree because it has fewer leaves to produce energy. Especially a heavy pruning on a hot day can literally “burn” the tree and dry it out.
• General stress: Trees, like people, suffer from stress when major changes occur. A willow that is pruned incorrectly or inopportunely is under stress: it has to heal wounds, compensate for lost leaves and defend itself against pathogens all at the same time, and at the time when it was actually in the midst of growing. This stress can lead to growth retardation the following season or increased susceptibility to pests.

In short, the health of your willow can take a big hit from thoughtless summer pruning. That doesn’t mean the tree always dies immediately – willows are tough guys and often sprout again – but any unhealthy intervention can take its toll in the long run. You’d rather see your tree grow old healthy, so prevention is better than cure.

Tips for safe summer pruning

Suppose you have to prune in the summer despite the drawbacks. Sometimes there is no other way: there is a dangerous branch hanging that needs to be removed now, or there is storm damage in July. In such cases, the tips below will help you prune as safely and responsibly as possible, for both you and the tree:

1. Prune minimally and thoughtfully. Limit your summer pruning to the bare essentials. Remove only the branch(s) that really cause acute problems. Leave the rest until winter. The less you prune away, the smaller the blow to the tree. Certainly don’t try to thin out the entire crown at once or drastically reduce the tree’s size in the summer. Removing a few small branches is usually fine; cutting off half trees is better not.

2. Choose the right time. Preferably prune on a cool, cloudy day, preferably in the early morning or late afternoon. Avoid pruning in full summer sun or during a heat wave – in high temperatures, the pruning wound dries out faster and the tree is already under moisture stress. Also do not prune right after heavy rain (slippery branches, dangerous to yourself, and damp conditions promote infections in wounds). A dry day with light cloud cover is ideal. Pruning in August is slightly better than pruning in June because the sap flow is already a little less exuberant by then.

3. Check for nests and animals. Before you put the saw in the tree, check carefully to make sure there is no bird’s nest in the branches or perhaps a squirrel or other animals using the tree. In the summer, chances are birds are nesting or young birds are in the tree. Never move or remove a nest – this is not only pathetic, but illegal. If you find a nest on the branch you wanted to prune, postpone that pruning or engage an expert who knows how to deal with it.

4. Use clean and sharp tools. Always prune with well-maintained, sharp loppers or saws. A sharp cut creates a smooth wound that heals faster. Bone tools produce ragged wounds and bruise the bark, which heals worse and is more likely to cause infections. Clean your pruning tools before use (possibly with alcohol) to avoid transmitting diseases from other plants. Especially when pruning multiple trees, disinfecting is smart.

5. Make the right cut. Cut or trim branches correctly: just outside the branch crown (the bulge where the branch comes out of the trunk) and not too far from the trunk, but not against it either. This is the best way for the wound to grow closed. Do not leave a long stump, as that piece of wood will die and may rot. But don’t saw into the trunk itself either, because then you will enlarge the wound unnecessarily. When in doubt: try small branch first so you can feel the technique. With thicker branches, always start with an undercut (saw in a bit from below) before sawing through from above, to prevent the bark from tearing.

6. Be careful and consider your own safety. Summer pruning often means working under a canopy of leaves, so make sure you have a good view of what you’re doing. Preferably wear safety glasses (against falling twigs and flying splinters) and gloves. If you are working on a ladder, make sure it is sturdy and straight, and preferably that someone is holding the ladder. Do not climb the tall willow yourself without climbing equipment or experience – that is asking for accidents. For high or thick branches, it is better to call in a professional, even if it is summer. If you are going to use a chainsaw, be sure to wear protective gear (saw pants, helmet with visor, hearing protection) and handle the saw with two hands. Safety always comes first! Rather a wild tree in the garden for a while than a visit to the emergency room.

7. Take care of the tree after pruning. Even if it’s a small pruning, give your willow some extra attention afterward. In summer, that means: make sure the tree gets plenty of water (especially in drought conditions) so it can absorb the loss of sap. You usually don’t need to cover pruning wounds on willows with wound balm – the modern view is that the tree itself can best seal its wounds. For very large wounds, however, you may want to trim the edges neatly to promote closing, but otherwise let nature do its work. Keep an eye on the tree in the weeks after pruning: if you see a lot of sap bleeding, you can try to keep the area around the trunk moist (don’t rub it on the wound, but give the tree plenty of water) so it doesn’t dry out. New water locks are best left alone until the next winter; don’t keep trimming, as this will keep the tree in a state of stress.

These tips will help you limit damage and risk if summer pruning does occur. But if at all possible, schedule your major pruning during the tree’s dormant period. That saves a lot of worry.

Alternatives to summer pruning

Suppose you have concluded that summer pruning is not ideal for your willow. So what can you do to still improve the situation without immediately pruning the tree midstream in July? Some alternatives and advice:

• Wait until fall or winter: It may sound lame, but patience pays off. Often a problem in summer (for example, lots of overhanging branches) is easily solved in winter with a good pruning. Keep in mind that the months of November through February are over in no time. You can make plans now: if necessary, mark with ribbons which branches you want to remove in winter. That way you won’t forget and you can live with it for the time being. By the time the leaves fall, tackle those branches purposefully.
• Perform light topiary pruning: If complete pruning is too severe now, you can choose to do only a very limited topiary in the summer. For example, shorten a few thin branches so they don’t rub against the gutter, or trim low-hanging twigs above the garden path. This is actually more tracking than actual pruning. You retain most of the foliage, but alleviate the most pressing complaints. In the winter, you can then prune more thoroughly. Think of summer pruning in this case as a stopgap measure to remove the worst nuisance, not to fully maintain the tree.
• Support or secure instead of pruning: If the willow has branches that are in danger of breaking (for example, from their own weight or from a crack you’ve discovered), you can take temporary measures without pruning right away. You could support a thick branch with a wooden prop, or tie two weaker branches high up in the tree together with a tension strap to reduce the chance of tearing. These are obviously temporary solutions, but they can help you get through the summer until you can prune at the right time or have a professional solution (such as crown anchoring) done. Just be sure to pay attention to safety: don’t sit unnecessarily under a risky branch and keep children away.
• Give the tree what it needs: A healthy tree is better able to take a beating. Instead of pruning, you can help your willow in the summer by providing optimal conditions. Make sure it gets enough water in drought conditions – a willow is a true water lover and is less likely to suffer from drooping branches or leaf fall with extra watering. Also, avoid damaging roots around the tree during the summer (for example, by digging or heavy loading); any stressor less is a nice bonus. A healthy willow can usually handle those few extra months without pruning just fine.
• Seek professional advice: Finally, if you have any doubts about the safety or health of your willow in the summer, don’t hesitate to ask a tree expert for advice. A certified arborist (European Tree Worker, for example) can assess whether immediate pruning is necessary or whether the tree will make it safely through the fall. Sometimes an expert can use a climbing inspection to check how firm the crown is and remove small problem branches, without pruning the entire tree. That’s a nice compromise: The tree remains largely intact until winter, and you sleep easy because the biggest risks have been eliminated.

If none of these alternatives suffice and you must do some major summer pruning, realize that this is an exceptional situation. Try to do it in stages (not all at once) or have it done by a professional with the right knowledge and tools. That way you limit the damage. But usually delaying until winter is the best move. Skipping summer pruning doesn’t mean you’re doing nothing – in fact, you’re doing the right thing by thinking ahead to the right time!

Frequently asked questions about summer willow pruning

Also read When is the best time to prune a hedge for more tips on the proper pruning period.

Also read: Get your tall tree pruned if you also want other large trees addressed.