From Wikipedia, the free encyclopedia:
A burl (British bur) 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. Burls are the product of a cambium.
A burl results from a tree undergoing some form of stress. It may be environmental or introduced by humans. 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. Insect infestation and certain types of mold infestation are the most common causes of this condition.
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. One of the largest burls known to man was found around 1984 in the small town of Tamworth, Australia. It stands 6.4 ft tall, with an odd shape resembling a trombone.
Burls yield a very peculiar and highly figured wood, one prized for its beauty by many; its rarity also adds to its expense. It is sought after by people such as furniture makers, artists, and wood sculptors. There are a number of well-known types of burls (each from a particular species); these are highly valued and used as veneers in furniture, picture frames, household objects, automobile interior paneling and trim, and woodturning. The famous birdseye maple superficially resembles the wood of a burl but is something else entirely. Burl wood is very hard to work in a lathe or with hand tools because its grain is misshapen and not straight.
Some burls are more highly prized than others, including ones originating in rural areas in central Massachusetts, northeast Connecticut, and as far south as Philadelphia. Some types display an explosion of sorts which causes the grain to grow erratically, and it is these burls that the artist prizes over all other types. These spectacular patterns enhance the beauty of wood sculptures, furniture, and other artistic productions. Burls are harvested by a variety of methods. Many redwood trees have them, but there are two things that hinder the harvest of redwood burls, the first being that removing a burl can cause the death of the tree. The second is the sometimes tremendous size of redwood burls; removing them can require the use of heavy equipment, which can be expensive and difficult to get to the tree's location.
