We assessed wood quality in common walnut using a combination of physical properties and structural features. Five common walnut trees were selected and processed in order to produce wood samples for further analyses.
The results showed a wide spread of values of structural features and of wood water content. The color indices were strongly grouped around the averages. All experimental distributions were stratified following at least one of the analyzed factors (tree and its structural directions i.e. longitudinal, radial, and tangential). The radial anisotropy was the most pronounced. The longitudinal stability of density and water content, the inter-tree stability of color saturation as well as the homogeneity of all color indices on the girth were noticed. The heartwood covered up to 12.5% of transverse section and included 1–10 growth rings. The annual rate of bio-accumulation allowed the separation of stages of radial development of the structure using the width of growth rings: juvenile wood, composed of the first 8–9 rings from the pith; a transition zone to the mature wood (10 rings); and mature wood under way to be formed. Wood density was not a reliable criterion for differentiating the sapwood from heartwood but brightness, redness and hue’s color could be used for this purpose.