You may have seen large bumps on the trunks of trees and wondered what they were. They’re called burls and to some people, they are worth a lot of money! Burls are knotty growths on the outside of trees that when cut open, have beautiful designs. These growths usually occur when the tree has been under some kind of stress, such as a sickness, an injury, or a fungal infection. The tree’s natural growth patterns are disrupted and they create burls. This growth is called cambial growth, and burls are formed to protect the rest of the tree from infection.
Burls can form on any kind of tree, but some trees are more susceptible to fungal infections. High quality burl generally comes from redwood, walnut, cypress, teak, and maple. Burls look ugly, but they don’t hurt the tree. Burls are covered in protective bark, even when they are underground. While burls aren’t harmful to the tree, some can grow so large and cause further stress to the tree by breaking the tree in half.
Burls can take up to 30 or 40 years to reach maturity, that is to say, reach the age where the whorls and swirls on the inside of the burl are fully formed. Burls can be removed from a healthy tree, but it must be done carefully and by a professional. Removing a burl from a tree without care can open a large wound on the tree and expose it to infection and disease.
Because of their unusual patterns, burls are sought after by artists, car manufacturers, furniture makers, sculptors, and many other fine craftsmen. The car company, Jaguar, uses walnut burl for the interior of their cars, and they even sponsor a 175 acre planting within the National Forest of the UK. Walnut burls are extremely rare and grow underground, so you don’t know their worth until you dig up the entire burl.
If you’re interested in selling a burl on your property, measure the burl and take pictures of it from several angles. A quality burl is covered in good bark with no signs of rot. To get the best deal for your find, contact a local woodturner who will be able to assess the burl and find a seller. The American Association of Woodturners is a good place to start to find a reputable woodturner.