Hardwoods come from angiosperms, which means the plant seeds are encased
in a “seed vessel” like a fruit or a nut. There are two types of
angiosperms: monocots (such as palm and bamboo) and dicots (such as oak
and rosewood). Almost all hardwoods come from dicots. Most dicots in
temperate climates are deciduous, meaning they lose their leaves during
winter dormacy. Dicots in warmer parts of the world don’t lose their
leaves — at least, not all at once. So, contrary to the standard
definition, not all hardwoods come from deciduous trees.
Softwoods come from gymnosperms, plants with naked seeds. As the seeds
develop on the cones, they are not encased in any tissue. Within this
botanical group, there is a subdivision of conifers, which are
characterized by needle and scale-like foliage. All softwoods come from
distinguishing factor between hardwoods and softwoods is how the trees
reproduce. Hardwoods grow from encased
seeds (oak, top),
softwoods from seeds arranged on
while interesting, make little difference to most craftsmen. To find the
traits that affect your woodworking, you must look closer.
Hardwood Cell Structure
Study a piece of hardwood under a microscope and you’ll find five major
types of cells. Four of these are longitudinal cells, running parallel
to the length of the trunk or limb.
Most hardwood tissue is composed of
fibers 100 times longer than
they are wide. These have thick cell walls, sometimes appearing almost
Interspersed among the fibers are
vessel elements. These appear
much larger in diameter and shorter than fibers, and they are always
aligned to form long, longitudinal pipelines. When sliced open, they
appear as pores in the wood surface.
You may also find a small number of tracheids and
with much thinner cell walls than fibers. These are few and far between
and are completely missing in some hardwood species.
The fifth cell type runs
perpendicular to the others:
Ray cells form radial pipelines running out from the center of the
The appearance of a hardwood’s
grain depends on the size, shape,
and number of each cell type. And because there are so many possible
combinations, hardwood grain is enormously varied. For example, the rays
can grow quite large, producing a pronounced
in some species. In
quartersawn oak, for example, the rays are the first thing you see. In
other woods, they are barely noticeable.
Grain differs with the
distribution of cells in the growth rings. When the cells in the summerwood are roughly the same size and density as the springwood,
the wood has an even grain texture. When the summerwood cells are
noticeably smaller and denser than those in the springwood, the texture
Vessel elements and the
pores they create also have a conspicuous effect. Hardwoods with large
pores are said to have an
open grain. Those with extremely small pores
(too small to be seen with the naked eye) have a
Softwood Cell Structure
Softwoods have a much simpler structure. Between 90 and 95 percent of
the wood is composed of tracheids, while the rest are
ray cells. There
may also be a small number of parenchyma cells. There are no fibers or
vessel elements, although some softwoods have resin canals lined with
Because there are no fibers in softwoods, they tend not to be as dense
or as hard as most hardwoods. And because there are fewer types of
cells, there is less variety in the grain and appearance. For example,
the absence of vessel elements eliminates the pores on softwoods. The
grain is neither open nor closed — these terms don’t apply to softwoods.
cells that make up hardwood.*
The quarter grain surfaces of lumber where the wood
species has large ray cells shows pronounced
long grain surfaces of Red Oak display an
grain pattern, while those of Honduran Mahogany are much more
cells that make up softwood.*
most wood tissue is composed of strands of cellulose fibers stuck
together with lignin, there are many other chemicals and minerals
embedded in this matrix.
Extractives, as the embedded substances are known, differ from species
to species. A particular mix is what gives wood its characteristic
color. But color is just one of the effects of extractives.
Extractives can effect the density and strength of the wood
species. The more extractives that are embedded in the fibers, the
denser and stronger the wood.
Many extractives are minerals. These act as fine abrasives, dulling
your cutting tools as you work.
Some are resinous and waxy substances. These build up as pitch on
the cutting surfaces of power tools and interfere with the cutting
action. They can also make a wood difficult to glue or finish.
Many are antibiotics, killing molds and bacteria that would cause
disease and rot. Woods high in these chemicals are resistant to decay.
A few of these antibiotic chemicals are toxic to humans as well as microbes
and have been known to cause or aggravate allergic reactions,
respiratory ailments, and other
microscopic, and chemical attributes all combine in a wood species to
give it distinct characteristics or properties. These can be divided
into two general categories,
mechanical properties and