A burl (British bur) is a tree growth in which the grain has grown in a deformed manner. It is commonly found in the form of a rounded outgrowth on a tree trunk or branch that's filled with small knots from dormant buds. Burls are the product of a cambium. A burl results from a tree undergoing some form of stress. It may be environmental or introduced by humans. Most burls grow beneath the ground, attached to the roots as a type of malignancy that's generally not discovered until the tree dies… (More on Burl)