AbstractThe longitudinal compressive and multi-directional bending properties after hydrothermal treatment of juvenile and mature elm wood were analyzed. Wood chemical composition and X-ray diffraction analyses were conducted in order to investigate the different properties of the juvenile and mature wood. Scanning electron microscopy was used to observe the wood’s microstructure during longitudinal compression. The results indicated that both juvenile and mature wood could bend multi-directionally and that their relative cellulose crystallinities increased after hydrothermal treatment. The hydrothermal-treated juvenile wood contained more hemicellulose with unstable net-linked polysaccharide and condensed lignin, higher relative crystallinities degree than did mature wood, and more spaces formed by the extractive separation of mature wood. The longitudinal compressive and bending performances of the juvenile wood were worse than those of mature wood. The relationship between variations of stress and strain was separated into two stages, both of which displayed linear increases. However, the stage after the proportional ultimate stress increased slowly and smoothly, confirming the formation of some folds in the wood cells.