The wood of precious native species is usually hard, deciduous and belongs to the group containing heartwood, a central part of the trunk colored to a distinct and characteristic color for a given specie, and the outer rings of the trunk, sapwood is usually contrastingly bright. The intense heartwood color is the result of the presence of tannins and other substances dissolved in wood juices, which are to protect the wood against moisture, fungus and vermin, which means that, in general, the heartwood species, in addition to their attractive contrasting coloration, are a much more durable material, resistant to moisture, rotting, mushrooms and insect attacks.
The saturation of the color and the share of colorful heartwood to light sapwood varies and depends most on the wood species and the age of the tree. Some trees, e.g. (Oak, Robinia, Larch) have a particularly wide, richly saturated heartwood and only a narrow border of sapwood, which makes their wood extremely durable and resistant to outdoor use. Others develop a narrow core of hardwood in later period of life (e.g. Ash, Elm).
Trees that do not color their heartwood at all (e.g. Lipa, Świerk) as well as from the heartwood-less group (e.g. Brzoza, Buk, Maple, Alder and Hornbeam) have quite similar to each other, light yellow-flesh color and homogeneous structure without clear grain pattern, which is why they do not look as picturesque and attractive as the heartwood species. In general, they also rot easier, and are mainly used in mass production and heating.
Below is an overview of the characteristics of heartwood species of wood, mostly deciduous, available for projects in a variety of forms, as beams, boards, slats, fragments of the trunk, branches and roots. The wood comes from Poland and is obtained locally in small quantities from private individuals, often from garden felling on home premises.