Hardwood is wood from Flowering plant . These are usually found in broad-leaved temperate and .[ Extract of page 134] In temperate and boreal ecosystem they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from angiosperm trees) contrasts with softwood (which is from gymnosperm trees).
Characteristics
Hardwoods are produced by
Flowering plant trees that reproduce by flowers, and have broad leaves. Many species are deciduous.
Those of temperate regions lose their leaves every autumn as temperatures fall and are dormant in the winter, but those of tropical regions may shed their leaves in response to seasonal or sporadic periods of drought. Hardwood from deciduous species, such as oak, normally shows annual
dendrochronology, but these may be absent in some
tropical timber.
Hardwoods have a more complex structure than softwoods and are often much slower growing as a result. The dominant feature separating "hardwoods" from softwoods is the presence of pores, or vessel element.[CRC Handbook of Materials Science, Vol IV, pg 15] The vessels may show considerable variation in size, shape of perforation plates (simple, scalariform, reticulate, foraminate), and structure of cell wall, such as spiral thickenings. Several specific microscopic features are used in the identification process of a hardwood species.[ Presentation by Dr. George I. Mantanis (Univ. of Thessaly, 2024)]
As the name suggests, the wood from these trees is generally harder than that of softwoods, but there are significant exceptions. In both groups there is an enormous variation in actual wood hardness, with the range in density in hardwoods completely including that of softwoods; some hardwoods ( e.g., balsa) are softer than most softwoods, while taxus is an example of a hard softwood.
Chemistry
The structural polymers of hardwoods are
cellulose,
hemicellulose, and
lignin.
The constituents of hardwood lignin differs from those included in softwood.
Sinapyl alcohol and coniferyl alcohol are the main monomers of hardwood lignin.
Hardwoods contain a smaller quantity of non-structural constituents, named extractives, than softwoods.
Applications
Hardwoods are employed in a large range of applications, including
fuel,
,
construction,
boat building,
furniture making, musical instruments,
Wood flooring,
Outdoor cooking,
, and manufacture of
charcoal. Solid hardwood joinery tends to be expensive compared to softwood. In the past, tropical hardwoods were easily available, but the supply of some species, such as Burma
teak and
mahogany, is now becoming scarce due to over-exploitation. Cheaper "hardwood" doors, for instance, now consist of a thin veneer bonded to a core of softwood, plywood or medium-density fibreboard (MDF). Hardwoods may be used in a variety of objects, but are most frequently seen in furniture or musical instruments because of their density which adds to durability, appearance, and performance. Different species of hardwood lend themselves to different end uses or construction processes. This is due to the variety of characteristics apparent in different timbers, including density, grain, pore size, growth and fibre pattern, flexibility and ability to be steam bent. For example, the
Wood grain of
elm wood (
Ulmus spp.) makes it suitable for the making of chair seats where the driving in of legs and other components can cause splitting in other woods.
Cooking
There is a correlation between density and calories/volume. This makes the denser hardwoods like
oak,
cherry, and
apple more suited for camp fires, cooking fires, and smoking meat, as they tend to burn hotter and longer than softwoods like
pine or cedar whose low-density construction and highly-flammable pitch make them burn quickly and without producing quite as much heat.
See also
Further reading
-
Schweingruber, F.H. (1990) Anatomie europäischer Hölzer—Anatomy of European woods. Eidgenössische Forschungsanstalt für Wald, Schnee und Landscaft, Birmensdorf (Hrsg,). Haupt, Bern und Stuttgart.
-
Timonen, Tuuli (2002). Introduction to Microscopic Wood Identification. Finnish Museum of Natural History, University of Helsinki.
-
Wilson, K., and D.J.B. White (1986). The Anatomy of Wood: Its Diversity and variability. Stobart & Son Ltd, London.
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