A subtle crack, whooshing drop, and loud thump.

After a heavy limb falls unexpectedly, we start to feel uneasy about our tree! Are other branches going to follow suit? Will the whole thing go down?  

Any tree problem is alarming, but sudden branch drop syndrome stands out. Without warning, large, mature trees that appear to be in good health lose limbs.  

Read on to learn more about this mysterious tree phenomenon.

Why did branches start falling off my tree in summer?

That sounds like sudden branch syndrome, also called summer branch drop or sudden limb failure. During calm, but hot, summer days, seemingly healthy tree limbs simply snap and fall off.  

We’re not quite sure why this happens. But some trees are more prone to this–specifically, aging trees as well as sycamore, oak, elm, eucalyptus and beech trees. 

What should I do if this happens?

Tend to your tree as soon as you notice a problem. The first fall might come unannounced, but trees afflicted by sudden branch syndrome may shed a few more.  

So, act quickly, assess your tree’s health and take measures to reduce injury or damage. More on that below!

Can I prevent this? 

That’s a tough question because we don’t know for sure why this happens!  

There are a few common theories about what causes sudden limb failure. Some experts say it’s triggered by high humidity within the tree’s canopy, which leads to a surplus of moisture that weakens the tree’s structure. Others think it stems from an internal tree issue, like bacterial wetwood. 

Even after decades of research, the cause is still up for debate. Because of that, it’s hard to say how exactly to prevent this.  

But there are a few steps you can take to decrease the likelihood of summer branch drop:

  1. See a large chunk of your tree on the ground? Have an ISA Certified Arborist® inspect the rest of the tree. They’ll look for dead offshoots, decay or other visible hazards. Then, because your tree could be at risk, plan to get it inspected annually for the next few years. 
  2. Get ready to trim! Of course, you’ll want to remove any unsafe tree limbs. But you should also see which sections of your tree may be at risk because of their weight or internal decay. Finally, your arborist may recommend pruning to open up the canopy, which reduces humidity. 
  3. Keep the tree as healthy as possible with regular plant health care practices. That means watering, mulching, trimming and fertilizing.

Not sure your tree’s structure is sound? Ask your local arborist to take a look. 


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