Burl
A burl (British "burr") is an outgrowth on a tree. Burls are often misunderstood. As it is the product of a cambium it may not be compared to any phenomenon in animals or humans. A burl is only a burl if it is filled with small knots from dormant buds. The famous bird's eye maple superficially resembles the wood of a burl but is something else entirely. Some say that burls are near knots but can not have knots themselves. The picture here seems to have knots in it.
Burls yield a very peculiar and highly figured wood. There are a number of famous burls (each from a particular species): these are highly valued and used as veneers in furniture and cars, or for woodturning.
In some tree species burls can grow to great size. Some of the largest occur in redwoods (Sequoia sempervirens): when moisture is present, these burls can grow new redwood trees.
The world's largest and second largest burls can be found in Port McNeill, British Columbia, Canada.
