Burl wood can be a challenging species to woodgrain, but the results are as visually interesting as the the actual wood. The burl is a protuberance on the side or root of the tree, a reaction of stress on the fibrous tissue.
The stress can come from a wound or bruise, insect bites, virus or fungus. Most species of wood have them, but only a few are spectacular enough to be cut. (tree below is from Olympic National Park)
Although they are taken from different parts of the tree, the pollard, the burl, and the root all produce similar figures, displaying an intricate grain structure and many knots (see figure).
Burls appear in many different types of wood, from the most common to the most exotic. Because the burl figure is always limited in extent, it is cut almost exclusively as small veneers and subsequently used for inlay, marquetry, furniture, and small decorative objects. In all these examples, burled wood is often combined with other wood species or with natural materials such s shagreen, tortoiseshell, or ivory.
Most commonly used burled woods:
Elm Burl, is very difficult to find these days due to the near extinction of the species. The yellow-white hardwood of the elm is mostly used in roots or burl, which has a warm orange color and features randomly spaced rounded dark knots interspersed with a lot of moire effects.
Ambonia burl. This tree is found only on the island of Ambon or Amboina in Indonesia. Its warm orange wood, which is flecked with thousands of tiny knots, is used exclusively for its burl figure.
Thuja burl. Found throughout the Northern Hemisphere, the thuja is a type of pine tree whose fibrous wood is dappled with many tear-shaped knots.