Burl

Measles bulbs from a beech trunk in Mecklenburg

Sessile oak with a large burl in the Brohmer Mountains.

A burl , even grain crop or wood goiter , or falsely as burl called, is a growth on the tree, which a grained wood yields.

nature

Measles bulbs are cell growths that are usually triggered by the bacterium Agrobacterium tumefaciens . This smuggles fragments of its own genome with plasmids into that of cells of higher plants and triggers uninhibited growth in the infested area. The tubers can be recognized by a clear thickening on the trunk, often in the lower trunk section.

Another cause of the formation of measles bulbs is the massive sprouting of dormant buds in a confined space. The growth of these tubers can be promoted, for example, by repeated mechanical removal of water veins.

Whether a growth on the trunk is a measles bulb can only be determined with certainty by opening it. There is a risk of confusion with the goiter, for example, which outwardly resembles the measles tuber, but did not arise from the shoot of dormant buds, but rather from the widening of tree rings. Therefore, when selling wood, tubers are added to submissions for the sale.

use

Burls of burl are almost always processed into veneer . Burl bulbs from walnut trees, which are often formed at the refinement points by grafted-on rice, are mainly used for furniture and interiors in luxury automobiles and in furniture construction.

As a very expensive solid wood, grain wood is used for the handles of expensive luxury knives or for turned writing implements such as pens and fountain pens. Particularly conspicuously grained precious wood is also used for the stocks of fine hunting or sporting rifles.

The reddish wood of the burl bulbs of the tree heather Erica arborea , which grow underground, is sold under the name briar and is used almost exclusively for the manufacture of pipe bowls .

Walnut burl wood is often incorrectly referred to as burr walnut , even though it is not wood from the root. The wood of the root stocks of nut trees, on the other hand, is worthless and not noticeably grained wood.

literature

• Franz Julius Ferdinand Meyen, Christian Gottfried Daniel Nees von Esenbeck: Plant pathology and plant teratology. Doctrine of the sick life and formation of plants, Haude and Spenersche Buchhandlung, Berlin 1841,
• NA Hartig: Textbook of plant diseases. For botanists - foresters - farmers and gardeners, published by Julius Springer, Berlin 1900.

Web links

Commons : burl bulbs  - collection of images, videos, and audio files

• Wood science (accessed on August 9, 2018)
• Pay attention to the signs of the trees (accessed July 3, 2020)
• Raw wood storage Raw wood sales (accessed on August 9, 2018)

Individual evidence

1. ↑ Bulbous ornamentation. In: Spiegel Online. May 5, 2004, accessed July 3, 2020 .