Burl
A burl or burr 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. Burl formation is typically a result of some form of stress such as an injury or a viral or fungal infection. More scientifically, a burl is "the result of hyperplasia, a greatly abnormal proliferation of xylem production by the vascular cambium".
Burls yield a very peculiar and highly figured wood sought after in woodworking, and some items may reach high prices on the wood market. Poaching of burl specimens and damaging the trees in the process poses a problem in some areas.
Description
A burl results from a tree undergoing some form of stress. It may be caused by a virus, fungus or Agrobacterium tumefaciens entering the plant through an injury. Most burls grow beneath the ground, attached to the roots as a type of malignancy that is generally not discovered until the tree dies or falls over. Such burls sometimes appear as groups of bulbous protrusions connected by a system of rope-like roots. Almost all burl wood is covered by bark, even if it is underground.In some tree species, burls can grow to great size. The largest, at, occur in coast redwoods and can engirdle the entire trunk; when moisture is present, these burls can grow new redwood trees. One of the world's largest burls can be found in Port McNeill, British Columbia.
Use
Burls yield a very peculiar and highly figured wood, prized for its beauty and rarity. It is sought after by furniture makers, artists, and wood sculptors. There are a number of well-known types of burls ; these are highly valued and sliced into veneers for furniture, inlay in doors, picture frames, household objects, automobile interior paneling and trim, musical instruments, and woodturning.Working the wood
The prized "" is not a species of a maple, but wood from a maple's burl.Birdseye maple of the sugar maple superficially resembles burr maple, but the causes of the bird's eye figure are unknown.
Burl wood is very hard to work with hand tools or on a lathe, because its grain is twisted and interlocked, causing it to chip and shatter unpredictably. This "wild grain" makes burl wood extremely dense and resistant to splitting, which made it valued for bowls, mallets, mauls and "beetles" or "beadles" for hammering chisels and driving wooden pegs.