Tree Burr, Bur or Burl
A burl (American English) or bur or burr (British 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, or in roots when tree dies) that is filled with small or large knots from dormant buds. A burl results from a tree undergoing some form of stress. It may be environmental or introduced by humans or insects.
….. and here in the Maritimes, we call 'em “TREE BURRS”.