The term 'Knotty Tree Growth' refers to the growth of trees that have knots in their trunks or branches. The knots are caused by a variety of factors, including disease, insect infestation, and environmental stress. The term 'BURL' is a four-letter word used to describe a large, rounded outgrowth on the trunk or branch of a tree, usually caused by a fungal infection. Burls can be found on many species of trees, and they often contain interesting patterns and colors.