During warmer weather, large branches may seem to fall from mature trees suddenly without warning or obvious cause. This is known as ‘summer branch drop’. This tends to happen in calmer conditions which can often catch people off guard.
Why do branches suddenly fall from healthy trees?
There isn’t a single reason for summer branch drop, but there are a few likely causes. In some cases, long, heavy limbs become stressed by the added weight of summer foliage or fruit. After a dry spell, a sudden downpour can also add extra weight in the form of surface water. Combined with internal weaknesses in the branch (such as old wounds, unseen cracks, or even decay) and the pressure can cause it to snap.
Arborists and researchers have suggested other possible causes over the years, but it often varies on a case-by-case basis.
Other possible causes may relate to old wounds or previous pruning sites that have weakened the branch over time. A change in internal pressure caused by high moisture levels from sudden rain could also be a factor. Many have also observed that a sudden change in the temperature or humidity may cause expansion or contraction in the wood.
Interestingly, the break often occurs across otherwise healthy-looking wood, and there may be no outward signs the branch was about to fall.
When is summer branch drop most likely to happen?
As the name implies, summer branch drop tends to occur during warmer months – usually late spring through to late summer. Weather conditions are often warm, humid, and calm with little to no wind. In fact, it’s the calmness of the weather that makes these events so surprising. Many people often expect branches to fall during storms or snow, not on quiet, sunny days.
Other cases have been recorded shortly after heavy rainfall, especially if the tree has experienced a period of drought beforehand.
Even though it’s difficult to predict exactly when it will happen, being aware of the conditions that increase the risks (hot spells, humidity, and recent rain after a dry period) can help you stay alert.
Are certain tree species more at risk?
Yes, some species are more commonly associated with summer branch drop. Broadleaved species that grow large, heavy limbs and a spreading canopy are more susceptible to summer branch drop.
Species that are commonly reported include:
- Oak
- Beech
- Ash
- Sweet Chestnut
- Horse Chestnut
- English Elm (historically)
While these trees are more commonly associated with the issue, summer branch drop isn’t limited to these species alone. Any large, mature trees with long, horizontal limbs may be at risk, especially if it’s growing in an open area where it’s likely to grow outward without the support of surrounding trees.
What are the warning signs of summer branch drop?
Like we’ve mentioned before – the main challenge surrounding summer branch drop is that it often happens without any clear warning. The tree might appear perfectly healthy from the outside, with strong growth and no visible damage, but this doesn’t always tell the full story. In some cases, you might notice long, heavy limbs stretching well beyond the main crown of the tree.
Other warning signs might include old pruning wounds, cracks in the bark, or scars from previous storm damage. A tree that has lost branches in the past may also have limbs at risk, especially if the structure hasn’t been reassessed or maintained since.
Sometimes, there are more subtle signs to pick up on – sagging limbs and strange creaking sounds can be early indicators that something isn’t quite right.
Is summer branch drop dangerous?
Yes, it can be. Because these branches often fall without warning, and often from a height, they pose a risk to people, vehicles and buildings below.
A breakage can leave the tree unstable, especially if other branches are under similar stress. Sometimes one branch is a warning sign that more may follow, especially if they share the same growth pattern or structural weakness.
Can I prevent summer branch drop?
There’s no guaranteed solution for summer branch drop, but there are a few sensible steps you can take to reduce the risk if you’re responsible for mature trees near people or property.
- Regular tree inspections – a professional arborist will assess the tree’s overall health, check for signs of stress, and observe how the branches are growing. If needed, they can recommend pruning and maintenance to reduce weight on the limbs.
- Be careful with watering – After a prolonged dry spell, it can be tempting to soak the base of the tree, especially if the leaves are wilting. However, sudden, heavy watering can sometimes do more harm than good. A change in moisture levels can increase pressure within the tree and cause further issues.
Keep an eye on previously damaged trees – If a tree has a history of shedding limbs or has suffered storm damage, it’s best to keep a careful watch on it. If you catch any issues that arise early, it may be possible to intervene before branch drop occurs.
What should I do if a branch falls?
First, avoid the area and don’t try to move the branch yourself if it’s large or unstable. If there’s damage to property or you’re unsure if the tree is safe, get a professional to check it. Even if the rest of the tree seems unaffected, it’s a good idea to inspect for any remaining risks.
Should I remove a tree that’s had summer branch drop?
Not always. One failed branch doesn’t necessarily mean the whole tree is unsafe. A proper inspection will help assess whether the rest of the tree is stable, or if further action is needed. In some cases, a bit of pruning or ongoing monitoring is all that’s required.
When should I get my trees inspected?
The best time to have your trees inspected is in spring, before the warm, dry weather sets in. This gives you time to carry out any recommended work ahead of summer, when the risk of sudden branch drop is at its highest. If a tree is close to buildings, paths or public areas, a routine check each year helps keep it safe and well managed.
If you’d like some reassurance about a tree on your land we’re happy to help. Get in touch with Dr Stump for clear advice and honest recommendations. Give us a call or send a Whatsapp to speak to the team.
