David R. Hershey dh321 at PGSTUMAIL.PG.CC.MD.US
Sat Oct 5 01:19:59 EST 1996

Whatever their cause, redwood burls are of great survival value because 
the buds in the burl can sprout if the parent tree dies. They allow the 
tree to going on living potentially forever, hence the name sempervirens. 
Redwood burls can be purchased from the giftshop at Muir Woods National 
Monument, Mill Valley, CA 94941, and will sprout nicely when placed in a
shallow layer of water. I've had some live several months. 

David R. Hershey
Snail mail: 6700 Belcrest Road #112, Hyattsville, MD 20782-1340

Adjunct Professor, Biology/Horticulture Department
Prince George's Community College, Largo, MD 20772-2199

Email: dh321 at pgstumail.pg.cc.md.us

On 3 Oct 1996, John R. Porter wrote:

> On Thu, 3 Oct 1996, John R. Porter wrote:
> I have looked at several sources to answer the question about the origin 
> of burls.  As a botanist and woodworker, I have more than a casual 
> interest in the structures.  Relatively few botany texts, whether for 
> theoretical or practical approaches, even broach the subject, but one 
> does.
> Saigo & Saigo, 1983, Botany, Principles and Applications, Prentice-Hall, 
> Englewood Cliffs, NJ, p 155.
> "Burls
>    Occasionally growth abnormalities occur, resulting in the formation of 
> bulbous growths called burls on the main trunk or branches (ref to Fig on 
> pg 156).  Burl formation may be stimulated by injury, disease, or 
> invasion by such parasitic plants as mistletoes.  Within a burl, the 
> cambium proliferates adventitious buds and abnormally large amounts of 
> xylem tissue, which become rippled and convoluted because it has no room 
> to grow longitudinally.  Dense, swirled patterns form in the wood, making 
> burls popular for decorative woodwork, such as bowls, veneer panels, 
> furniture, and pipes."
>  Another reference, of a woodworking nature, is Constantine, Albert J., 
> Jr. (rev by Harry J. Hobbs), 1975, Know Your Woods, Charles Scribner's 
> Sons, NY, p 64:
> "Burls are responsible for the formation of a number of interesting 
> natural designs.  A burl is an abnormal, wartlike excrescence on the 
> trunk or branches of a tree.  Examined closely, it may appear to consist 
> of a great mass of 'eyes' or dormant buds.  The surface of such a bulge 
> may be smooth or rough.  In either case the alignment of the fibers is 
> very irregular and the burl is thus gnarled.  Because of this many 
> bizarre figures are derived from veneers cut from burls.  Causes of burls 
> are imperfectly understood and the following reasons have been advanced 
> to explain this unusual growth:  injury from frost, fire or mechanical 
> contact; and irritation of the cambium by bacteria, fungi and possibly 
> viruses.  A legend states that wounds inflicted by woodpeckers cause 
> burls.  However, this is easily discredited in that trees produce burls 
> in regions where woodpeckers do not exist.  Burls can and do grow on all 
> species of trees; however, they are found more commonly on certain trees, 
> as for example, the redwood (_Sequoia sempervirens_)."
>  -- 
>  John R. Porter
>  porter at shrsys.hslc.org

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