Birch, American

Introduction

Of the nine or more species of Betula found in North America, only two or three are considered commercially important. The timber is diffuse porous and is hard, heavy, strong and tough. The principal species producing North American birch are described below.

• Paper birch: Betula papyrifera Marsh.
• Yellow birch: Betula alleghaniensis Britt. Syn B. lutea Michs. (principally) and B. lenta L.

Note: North American specifications sometimes refer to selected and unselected. These refer to the colour and not grade and means the timber has or has not been selected for uniformity of colour. Thus sapwood might be called white birch (sometimes confused with Betula papyrifera) and the heartwood red birch.

Environmental

Not listed in CITES. Believed available from well-managed sources. Check certification status with suppliers.

Distribution

Paper birch: It has a very wide range from the Yukon to Hudson Bay and Newfoundland, spreading to the eastern parts of the USA.

Yellow birch: It is found from the Maritime Provinces of Canada westward to the east side of Lake Superior, and from the west end of this lake to the Lake of the Woods, extending southwards over the border into USA reaching Long Island, northern Delaware and Tennessee.

The tree

Paper birch: Although the tree may reach a height of 21m with a diameter of 0.5m it is more commonly 1 5m to 18m tall with a diameter of 0.3m usually with a clear cylindrical bole.

Yellow birch: The largest of the North American birches, reaching a height of 30m and a diameter of 1 m on favourable sites, but more often it is from 18m to 24m tall with a diameter of 0.75m having a clear bole with moderate taper.

The timber

Paper birch: The wood is creamy-white in colour, with a fine, uniform texture, weighing about 710 kg/m³ when dried.

Yellow birch: The sapwood is light yellow in colour and the heartwood a distinct reddish-brown, with the growth-rings marked with a narrow line of darker colour. There is a wide range of colour differences in unselected parcels, but yellow birch is one of the few woods which when finished with a medium or dark coloured stain will not show a marked difference between sapwood and heartwood, hence there is a saving in cost in using unselected stock as opposed to selected white or red birch.The wood is straight-grained, and the texture is fine, and even. The weight is about 710 kg/m³ when dried.

Drying

Dries slowly, but with little degrade. 

Strength

Paper birch: A medium-hard timber with general strength properties some 10 to 20 per cent inferior to those of yellow birch.
Yellow birch: Yellow birch is a stronger and harder wood than European birch, being about 60 per cent harder when dry, and about 15 per cent stronger in compression along the grain and stiffer in bending. It equals European ash in toughness and in resistance to shock loads.

Working qualities

Good.

Paper birch: Works reasonably well with all hand and machine tools, with only moderate dulling of cutting edges. Curly-grained material is liable to pick up, but a good finish can be obtained with care. The wood glues satisfactorily.

Yellow birch: Works fairly easily with only a moderate dulling effect on cutting edges, and finishes smoothly and without difficulty if the stock is straight-grained and clear. Curly-grained material, and disturbed grain in the vicinity of knots is liable to tear and pick up during planing and moulding, and a cutting angle of 1 5° or less is needed. The wood turns well, and with care glues satisfactorily. It takes stains and polish extremely well, and on account of the light tone of birch wood, it is well adapted to delicate colour stains. It is unexcelled as a base for white enamel, because its uniform, dense surface, free from large groups of pores, guarantees a permanent smooth surface.