Reaction wood
From WikiWOOD
Reaction wood is abnormal wood growth, formed typically in both branches and leaning or crooked trunks of trees, and is caused as a reaction to the mechanical stress the wood grows under. It has different anatomical and physical characteristics than normal wood.
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Growth
- In hardwoods, reaction wood is called tension wood. Tension wood forms above the affected part of the plant, pulling it up. It is composed almost entirely of cellulose.
- In softwoods, reaction wood is called compression wood. Compression wood forms below the bent part, pushing it up. Compression wood is rich in lignin.
Problems with reaction wood
- Boards cut from it will invariably twist.
- Compression wood is often very dense, hard, and brittle.
- Woolly surfaces.
- Excessive longitudinal shrinkage.
- Uneven acceptance of stain.
- Failure under load.
- Cracks and split more easily when nailed or screwed.
Identifying reaction wood
When selecting boards, there are several clues that it may contain reaction wood:
- Crookedness
- Unusually hard wood fibers
- Small fuzzy fibers on surfaced hardwood
Further reading
- Wikipedia has an article about Reaction wood
- A general theory for the origin of growth stresses in reaction wood: how trees stay upright RK Bamber - IAWA JOURNAL, 2001
- Wood Formation in Trees C Plomion, G Leprovost, A Stokes - Plant Physiology, 2001
