Last week when we were walking around DC we saw this specimen of a tulip poplar tree.
These unusual growths didn't happen overnight, and there were more on this one tree than I think I have ever seen. The tree was still growing fairly well, leaves were dropping everywhere since it was so dry in Washington DC, but it was not dying, nor do I think it will any time soon. But what exactly are these growths and what do they mean?
The growths are called burls. A burl is formed when something disrupts the natural growing cycle of the tree. It could be a wound that lets in a disease, but they are usually either a bacterium, a fungus or a virus of some sort. Usually the tree remains generally healthy, but in this one section, the growth becomes distorted. Obviously, the xylem inside is still doing its job sending water and nutrients up the tree. There is some thought that burls are associated with dormant buds, and based on the spacing of these burls, I would have to agree that is what it looks like in this particular instance.
Why this tree continues to produce burls, I also don't know, but it is definitely an interesting looking tree on the outside.
While the outside of a burl may look pretty unappealing, for wood turners, the inside can be amazing. Most wood comes from straight planks where the grain of the wood is pretty straightforward. In a burl, the tree's cells have gone crazy and are all twisted and gnarled. This can create some interesting and complex patterns, and burled wood is highly valued.
Unfortunately, burls do take some time to grow, and you can't just cut a burl off the trunk of the tree and expect the tree to survive. While the burls themselves seem to do relatively little harm to the tree, removing them would leave large wounds. If you have a tree with burls in your yard, just enjoy them. The only way to harvest burls is to cut down the entire tree.