INTRODUCTION
Woodworkers do not need a degree in wood science
or biology, but they do need a certain basic knowledge
regarding the converted (sawn) timber from differ-
ent commercial species of felled trees, its often unruly
behaviour and defects and its suitability or not for
certain jobs. Such basic botanical knowledge – aimed
at briefly here – is an essential foundation upon which
to develop an understanding of working with this
fascinating and rewarding material.
GROWTH AND STRUCTURE
Trees are comprised of a complex structure of micro-
scopic cells which take up sap (moisture containing
mineral salts) from the soil via the roots, through the
sapwood to the branches and the leaves, where it is
converted into food and fed back to the new, inner
bark (or bast) in the cambium layer. The cambium
layer conveys the food to the growing parts of the
tree via the medullary rays. Another group of cells,
which form the bulk of the hardwoods’ structure, are
the fibres. These provide mechanical strength to the
structure of the tree. Botanically, the tubular cells of
softwood are called tracheids and the cells of hardwood
are called vessels or pores.
CLASSIFICATION
Trees are classified botanically, using two- worded
Latin names such as Araucaria angustifolia (Parana
pine), Quercus robur (English oak), etc; and they are
also classified commercially into softwoods and hard-
woods. However, these universally accepted trade
names must not be taken too literally, as some soft-
woods are hard and some hardwoods are soft. Parana
pine, for example, is botanically a softwood which is
quite hard – and Obeche (Triplochiton scleroxylon), a
hardwood, is quite soft. The names really refer to the
different growth and structure of the trees and their
use in a commercial sense.Softwood
Softwood refers to timber from coniferous trees – cone-
bearing trees with needle- shaped leaves – which are
mostly evergreens and are classified as gymnosperms.
These include the pines and firs, etc. Such species
are used extensively for joinery and carpentry work
and are marketed as being either unsorted or graded
according to the straightness- of- grain and the extent
of natural defects (described later).Redwood and whitewood
Softwood is also described as being either redwood or
whitewood. Redwood refers to good quality softwood
such as Scots pine, Douglas fir, red Baltic pine, etc,
which has very close, easily discernable annual rings
denoting slow, structural growth (a necessary ingredi-
ent for strength), a healthy golden- yellow or pinkish-
yellow colour and a good weight – and whitewood
usually refers to a poorer quality of softwood such as
a low grade of European spruce (picea abies from the
pinaceœ family), which has very wide (barely discern-
able) annual rings denoting fast growth and a lack
of the required thick- walled, strength- giving cells
(tracheids), a pallid, creamy- white colour and an
undesirable light weight. It usually has hard glass-
like knots – which splinter and break up easily when
planed or sawn – and it is not very durable.Hardwood
Hardwood refers to timber mostly from decidu-
ous trees that have broad leaves which they shed in
autumn. These are classified as angiosperms and include
afrormosia, iroko, English oak, the oaks from other
countries, mahoganies, beeches, birches, etc. The first