A burl (American English) or bur or burr (UK English) 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 is filled with small knots from dormant buds. What do burls look like? A burl may form a rounded bump on one side of a tree, or partially or completely surround the tree. The shape may be smoothly curving or irregular with twists and fissures. They fascinate me...