Chapter 6 – Reaction Wood

Reaction wood is the characteristic wood formed as part of the gravitropic response of trees and shrubs, and generally occurs in leaning stems including branches. In conifers, reaction wood is known as compression wood while in hardwoods it is known as tension wood. Compression wood generates compression stress on the lower side of the leaning stem, which acts to push the stem back to the upright position. Tension wood generates tensile stress on the upper side of the leaning stem, which acts to pull the stem back to the upright position. Both wood types have abnormal shrinkage and other properties, which result in reaction wood being considered a defect in sawn timber.