What Are Tree Burls?

Does one of the trees in your backyard have a large, knobbly lump? Don’t worry! It’s probably just a burl. Here’s what you need to know about this harmless growth.

A tree burl is a large woody, rounded swelling found near the base and trunk of some trees. Burls can grow on any species of tree. However, popular tree species that regularly grow burls include walnut, elm, maple, cherry, oak and ash.

What Causes Burls on Trees?

Experts haven’t been able to pinpoint the exact cause of tree burls. It’s generally believed that burls form when a tree’s growth hormones are disrupted due to stress, causing abnormal cell development. The exact type of stress is unknown. However, burls may develop because of insect infestations, bacteria and fungi growth, mistletoes and environmental injuries, such as freeze damage.

Do Tree Burls Need to Be Removed?

There’s no reason to remove burls as they don’t hurt the tree in any way. On the contrary, they can be helpful. Burls often form over injuries to help keep the tree alive. Removing a burl could leave behind a large wound, exposing the tree to unwanted stress that could kill it.

Burls Are Celebrated

Although unsightly to some, burl wood is prized by woodworkers for its unusual grain patterns and interesting colours, ranging from light chocolate to dark brown. Burls can’t be propagated or replicated, making them sought after for their unique beauty.

Burr Knots Vs. Tree Burls

Tree burls can easily be confused with burr knots. Unlike burls, which are harmless, burr knots are masses of small root initials. Burr knots can cause several problems for a tree. They can weaken the tree’s structure, stunt its growth and provide a way for insects and pathogens to enter the woody vegetation. Apple trees are particularly susceptible to this type of growth.

Are you unsure whether your tree has a burl or might be affected by some more-troublesome issue? The arborists at ArborCare® can visit your property for a consultation and assessment. We’ll analyze the health of your tree to determine the best course of action. You can count on us to care for and preserve your trees.

Schedule a Tree Consultation in Western Canada

Since 1983, the expert arborists at ArborCare have provided residential and commercial tree care services in Western Canada, including stump grinding, tree pruning, tree planting, and plant management. We also offer storm and disaster services. We serve customers in Calgary, Edmonton, Kelowna and Winnipeg. Contact us today for more information about our services or to schedule a consultation.