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Name: Eldonna
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How are tree burls formed?

Dear Eldonna, the following should be informative. Sincerely, Anthony R. Brach

"burl: 1) A hard, woody outgrowth on a tree, more or less rounded in form, usually resulting from the entwined growth of a cluster of buds. Such burls are the source of the highly figured burl veneers used for purely ornamental purposes. 2) In lumber or veneer, a localised severe distortion of the grain generally rounded in outline. "

Redwood Burls "Burls in coast redwood are masses of stem tissue where elongation of the many stem tips has not occurred. They are anatomically similar to tissues in eucalyptus called "lignotubers" by the Australians. Burls develop from axillary buds in the seedling redwood. This "basal burl" (sometimes called a bud collar) persists, growing larger throughout the life of the tree. The dormant stem tips continue slow growth and branching, but do not elongate. Unlike aerial stems of redwood, burl tissue grows downward. It forms an enlarged mass near the base of the tree above or below the soil surface. Burl tissue overgrows the root tissues at the base of the tree. Burls may also occur well up the main stem and on branches. Adventitious (hanging) roots often develop from burls, particularly near the soil, but no stems develop on redwood roots. "Stump" sprouts from the burl are often incorrectly called "root" sprouts, but there is no known instance in which stems have developed from root tissue in redwood. Dormant buds rapidly elongate after the biochemical dominance of the main stem is removed (such as when the tree is cut). In undisturbed forest stands, a few trees may sprout from the burl. These sprouts, growing under the canopy of the main stem, are at a physiological disadvantage and rarely reach large size. In this regard, they are like branches which eventually die when severely shaded by other branches. "

Anthony R. Brach, Ph.D.

They are basically benign tree tumors. They occur when a twig bud fails to grow normally, differentiating into the tissues needed for forming a limb, and instead just multiplies and multiplies and multiplies its bud cells. That's how you get the round growth with an irregular grain structure.

Many burls will sprout when placed into water, forming normal-looking shoots. Apparently the water saturation somehow helps them "remember" that they are, after all, limb buds.

Richard Barrans Jr., Ph.D.

Usually response to some sort of injury or invasion that triggers a response in the cells surrounding the area, causing unusual growth - a little analagous to cancer in animals but does not spread beyond immediate area and usually doesn't harm the tree, also a little analagous to scar tissue.

J. Elliott

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