Year after year, we come to expect the brand-new flowers, fruits and foliage that grow on our trees.

What we don’t expect to see are large bulges growing on the branches and trunks. What are those bumps on trees?

The round, swollen-looking growths found on tree wood are called burls. Here’s what you should know about them, including when they should or shouldn’t be a cause for concern.

Where do bumps on tree branches and trunks come from?

The cause of tree burls is a bit of a mystery, so it’s hard to pinpoint the one reason they’ve appeared on your plant.

In general, burls develop because of invasions (bacteria, fungi, and insects) or stressors (freeze damage and environmental injury). Some individual trees have a genetic predisposition to produce burls while nearby trees do not.

Are burls bad for trees?

Usually not. Burls typically don’t do any harm to trees. On rare occasions, a burl may disrupt the tree’s vascular system.

As it turns out, though, getting rid of them would pose the real risk. Cutting burls would leave large wounds on your tree’s trunk and branches, which could lead to an infection or weaken the tree's structural stability.

It’s best to not remove the bumps on tree branches or tree trunks. If you please, you can clip away sprouts that come out of the burls.

When should I be worried about burls on trees?

Burls themselves won’t cause problems for your tree, but you should get to the root of their growth and address it.

Since burls could be a product of insect or fungi damage, check for any other signs that point to an insect infestation. Look for small holes in the trunk and branches, sawdust, or insects crawling around.

Also, inspect your tree for signs of decay, including cavities, missing bark, root damage or wounds.

Check your tree for these 6 worrisome signs to make sure it doesn’t need to be removed!


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