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Cross-section through a yew trunk (the dark heartwood is clearly differentiated in color from the light sapwood)

Heartwood (depending on the context also colored core ) denotes the physiologically no longer active, mostly dark, inner zone in numerous tree species in the trunk cross-section, which is clearly different from the outer, light sapwood . It arises from secondary metabolic processes of the dying parenchyma in the inner sapwood.

Real heartwood

Cross-section through a pine trunk with heartwood

Real heartwood contains predominantly colored, mostly phenolic ingredients (core substances), which impregnate the cell walls and usually increase the durability of the wood . The tree also interrupts the connections between the cells by closing the pits (coniferous wood) or by vertifying the vessels (hardwood), so that capillary exchange is no longer possible. Heartwood is dead wood (see also nucleation ). Mature wood is also heartwood, but does not stand out from the sapwood in terms of color. The previously common distinction between heartwood and ripening wood is out of date. Podocarpus forms z. B. a light but durable mature wood (= heartwood), while the spruce forms a less durable mature wood . Today we speak of compulsory and optional coreing. Obligatory corers form real heartwood, while optional corers can form a false core .

False core

Ash trunk with optional nucleation (false core)

Numerous tree species core optionally and form a so-called false core due to external influences (mostly injuries) . However, this does not have increased durability and is characterized by its structure, which is often not very homogeneous in color. The core substances that are formed are only located in the cell lumen ; the cell walls are not impregnated. When using wood, the wrong core is usually considered to be an optical wood defect and therefore a value-reducing factor. However, it does not affect the strength of the wood.


compulsory cores (real heartwood trees).

Cross-section through a spruce trunk with mature wood (light heartwood)
  • The pine ( Pinus spp.) Is a real heartwood tree. The core (reddish) of the pine wood differs significantly from the sapwood (white-yellowish). In the case of pine poles, the sapwood is protected with wood preservatives.
  • The oak ( Quercus spp.) Is a heartwood tree in which the sapwood may not be used untreated outdoors, as it is not permanent.
  • The very hard and expensive ebony has a deep black core and a light sapwood.
  • Podocarpus , the stone pulp, forms a light-colored but durable heartwood (mature wood)
  • Spruces ( Picea spp.) Form light-colored, less durable heartwood (mature wood)
  • The sweet chestnut ( Castanea sativa ) also forms a relatively durable heartwood.
  • The Douglas fir ( Pseudotsuga menziesii ) and the black locust ( Robinia pseudoacacia ) both form nuclei.
  • The larch ( Larix )
  • The teak tree ( Tectona grandis )
  • Rosewood ( Dalbergia )
  • Mahogany (Meliaceae)
  • The European yew tree ( Taxus baccata )
  • The real walnut ( Juglans regia )
  • The Elm ( Ulmus )

Facultative corers (can form false cores):

  • The heartwood of the bird cherry ( Prunus avium ) is not a real heartwood, but a false core. It's not permanent. Since the color difference between heartwood (red) and sapwood (white) is very intense, the sapwood is cut away for high-quality furnishing woods.
  • The ash ( Fraxinus excelsior ) often has an olive-colored core ("olive ash ").
  • The beech ( Fagus sylvatica ) forms an often cloudy red heart in old age, which used to be completely undesirable, but is now e.g. T. in furniture construction as core beech is used.

Heartwood reagent

First cut pine wood, mixed with heartwood reagent. Wooden stick with a branch: high levels of tannins in the branch area

Due to the aromatic structures present in the heartwood of some tree species, the so-called tannins / tannins , there is a distinguishing feature compared to sapwood. This can lead to direct visual differentiation or it can be exploited by coupling with diazonium salts to give colored products. The "classic" reagent for the detection of pine heartwood is prepared from 2 components, solutions A and B.

  • Solution A is prepared by adding 5 g of 25% HCl, which is prepared from 25 ml of 37% HCl and 12 ml of H 2 O. Then 1 g of benzidine (be careful: carcinogenic !) Is added, made up with 200 ml of H 2 O and homogenized.

--- Instead of benzidine, it is better to use sulfanilic acid (Xi - irritating), whereby only a light orange color is achieved ---

  • Solution B is prepared by dissolving 20 g of sodium nitrite (NaNO 2 ) with H 2 O and making up to 200 ml.

Equal parts of the two solutions are mixed immediately before use. After applying it to the end grain surfaces, the heartwood becomes apparent after a short time with a deep red color.

See also


  • J. Bauch: Natural variations of wood structure due to secondary changes. In: Mitt. Bundesforsch.-Anst. Hamburg forest and timber industry. 131. 1980, 69-97.
  • Schütt, Schuck, Stimm: Lexicon of tree and shrub species . Nikol, Hamburg 2002, ISBN 3-933203-53-8 , pp. 169-170 .

Web links

Wiktionary: Heartwood  - explanations of meanings, word origins, synonyms, translations