What Causes a Burl in a Tree on Your Property?

What causes a burl in a tree? These natural oddities have fascinated nature enthusiasts and woodworkers alike for centuries. 

As Temple Hills’s top-tier tree service, we at Hernandez Complete Tree Service know the ins and outs of arboreal phenomena. Keep reading as we offer some insight on tree burl formation and why you shouldn’t cut them out without a second thought.

Understanding Burl Formation

Tree burls refer to unique, rounded outgrowths that can appear on the trunk or branches of a tree. Picture a large, knobby protrusion, somewhat akin to a wart on the surface of the tree. 

They vary greatly in size—some can grow as small as a golf ball, while the biggest documented ones span 20 feet in height and width and weigh over 20 tons. Larger growths often reflect a tree’s age; they need to have lived a few hundred years to form them.

Burls also have a rough textured surface. If you get up close, you might notice that the grain pattern inside them is incredibly intricate, as it swirls and loops in ways that the rest of the tree’s wood does not. 

A Woodworker’s Treasure

Burls hold a unique place in the world of art and craftsmanship. When cut and polished, the wood from a burl reveals a complexity and depth of patterns not found in the rest of the tree. This makes it exceptionally valuable for furniture making, sculpting, and creating decorative pieces. 

What Triggers Tree Burl Growth?

What causes a burl in a tree? Experts agree that they form when bud growth cells develop abnormally. 

They begin dividing in multiple, random directions instead of forming straight branches or stems. This results in a more rounded structure that sticks out from the tree’s natural line profile. Burls also form underground in place of roots.

Factors Causing Tree Burls

While the precise reasons for burl growth remain somewhat of a mystery, some speculate that the main culprits include:

• Physical damage: Did your tree sustain significant injury due to landscaping, construction, or even a particularly harsh storm? These stressors can trigger mutations in its cells.
• Pest or pathogen attacks: Trees may respond to infections and infestations by producing extra cells to isolate and protect the affected area.
• Genetics: Coastal redwood, cherry, ash, oak, maple, walnut, and elm are particularly prone to developing burls, which could hint at inherent genetic predispositions.

Should You Remove Any Burl Development in Trees?

The strange appearance and unexpected emergence of a burl might prompt some people to consider removal. Don’t act hastily, though. 

Burls themselves don’t harm the tree, but cutting them might. It can expose the tree to pathogens, weaken its structural integrity, and disrupt the flow of essential nutrients when done improperly. 

Burr Knots Are Another Story

Many easily mistake burr knots for burls due to their similar knobby appearance, but they’re an entirely separate phenomenon. 

Burr knots consist of clusters of adventitious roots that form on the surface of the wood, usually on the trunk. They tend to form in response to stress or injury. 

Knots can, unfortunately, leave the tree susceptible to damage and disease. You must address them early if you aim to maintain the affected specimen’s health and longevity.

Consult a Local Arborist

What causes a burl in a tree remains a topic of ongoing research and curiosity, but it’s clear they represent a part of the tree’s life story. When you suspect burr knots forming, though, err on the side of caution and seek an expert assessment. That’s where our crew at Hernandez Complete Tree Service comes in.

Call 240-299-4639 or read more of our blog and learn how to spot a healthy tree.