What Causes a Burl in a Tree?

what causes a burl in a tree

What causes a burl in a tree? And, incidentally, what counts as a burl, a gall, or one of the many other growths you find in a tree?

Brooke Tree Service, Dover’s excellent tree service, explains more below.

What is a Burl?

Burl wood is a big business for furniture manufacturers trying to create unique or custom designs in their wood products. However, if you’re a tree grower, you may be more concerned about what these formations mean for your tree.

You can easily distinguish a burl from normal growth because it’s bumpy, swollen, or bulging on the tree trunk. It may be a small smooth bump or have a rough texture, and it may also encircle a branch. Also, if tree care services were to open up that slice of wood, you’d see lovely grain patterns that woodworkers would love to get their hands on.

What is a Gall? 

A gall is something quite different from a burl. They’re smaller and appear on the branches and leaves but aren’t part of the tree. Usually, insects cause these abnormal growths.

What is a Burr Knot? 

Unlike burls, burr knots form from a mass of roots and damage the infrastructure. They hinder growth and invite disease and bugs to the trunk, especially in apple trees. If you see any type of growth in your tree and you’re unsure whether or not it represents a non-harmful tree condition, it’s best to call in professionals like Brooke Tree Service. 

What Causes These Growths in Trees? 

So, what causes a burl in a tree? Arborists aren’t sure. What we do know is that it happens when tree buds grow abnormally. 

For example, instead of growing a branch, the cells divide and form a round shape. It will grow burls in concentric rings instead of growing outward to form a new branch. Some experts believe it may be due to stress in the tree, and if so, burls are a potentially beautiful side-effect. 

Trees face stress for the following reasons: 

  • Disease
  • Fire damage
  • Pest damage
  • Windburn
  • Scalding
  • Mechanical wounds
  • Drought
  • Other environmental factors

Are Burls Dangerous for the Tree? 

While nobody knows for sure, arborists are relatively certain that anything that distresses the tree may play a role in forming burls. But no, burls don’t endanger the tree. They’re simply one of nature’s beautiful mistakes. 

If your tree has one, smile. However, if you’re concerned, you can always call a team like Brooke’s Tree Service to take a look.

What to Do About Burls

The best course of action for burls is to leave them alone. Removing it will leave a large open wound and put your tree at risk of disease or pest infestations. Plus, if it does manage to heal properly, it will leave an ugly scar.

Contact Us for Professional Advice!

No matter what causes a burl in a tree, a tree arborist can assist you with your questions and concerns. Do you need to nurse a tree back to health or find advice on proper planting? Call Brooke Tree Service at (508) 613-5044 today to schedule service in Dover, Massachusetts.


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