What Are Tree Burls and How Do They Happen?

A tree burl (or "wood burl") is a bulbous, woody growth that you may spot on a trunk or branch. A burl forms as the result of stress that its tree has undergone.

Though burls can raise concerns for new tree owners because of their strange appearance, they're quite harmless: the presence of a burl doesn't signal any problem in tree health you need to address. Some people feel burls mar the appearance of a tree, but artisans value them as raw materials for making high-end furniture, vases, and more.

Learn what tree burls are, how they happen, why creative types are fascinated by burls, and how to harvest one if your own creative side finds inspiration.

What Is Burl Wood?

Tree burls can even form below ground level, but, since they go unnoticed, we are usually only aware of the burls that form on a tree's trunk and/or branches. The size of burls varies greatly, with the larger ones being of greater interest to woodworkers (some, for example, are large enough to be crafted into table tops). The shape is irregular but generally rounded.

If you don't like the look of a tree on your property having one of these deformities, resist the temptation to cut the burl off. Doing so would leave an open wound that would invite disease into the tree. You should either learn to love the burl as an oddity of nature or have the whole tree taken down.

How Do Tree Burls Grow?

Researchers are only just beginning to understand exactly how burl wood grows (if we knew exactly, we could have burl farms instead of relying on nature to produce burls). But the likely explanation is as follows:

Stress is the origin of burls. These misshapen bumps are the result of their host trees fighting stress, which triggers a defense mechanism. Examples of stress-causing conditions range from insect or fungal infestations to the sapping of a tree's strength by parasitical mistletoe.

The triggering of this defense mechanism causes the normal processes of tree growth to be thrown out of whack (thus the unpredictability associated with burls). In response to the stress, tissue from unopened foliar buds begins to build up. The burl may continue growing for decades; during all that time, new, undeveloped bud tissue continues to build up in layers. As long as bark covers the exterior of the burl, the tissue is protected from any harm.

Harvesting Burl Wood

Since you can't cut a burl off a tree without damaging the tree, part of the harvesting process is cutting down the whole tree. If there are multiple trees on your property with burls on them, practice first on a smaller tree.

Once the tree is down, make two cuts in the tree itself, one a few inches below the burl, the other a few inches above it (some of the burl grain you're going to want to keep extends into the tree itself). Apply end grain sealer (sold at woodworking supply stores) to the ends to help with the preservation. Store the burl in a dry place so that it can be drying out while you consider what you wish to do with it.

Why Is Burl Wood So Popular?

To begin to answer this question, we note that, just like human fingerprints, no two burls are alike. The grain inside of each one is unique, and you never know what the grain pattern is going to be until you expose the inside.

This means that, if you have an object in your decor made from burl wood, it will truly be a one-of-a-kind piece that no one else in the world has. Burl wood adds stunning beauty and visual interest to a room.

Uses for Burl Wood

Examples of how burls can be used include:

• As veneers for furniture
• As inlays in cabinets or musical instruments
• In wall panels
• As accents in flooring
• To create smaller pieces such as bowls, boxes, or vases