Selecting timber tree species
Any timber component destined for selling should ideally be marketable, high quality (favouring deciduous), fast (and straight) and upright growing, deep rooting, wind firm and suited to the site. Durability of timber is also very important when trees are grown for estate use. These qualities are not always easy to obtain, especially from deciduous trees, most of which grow with a poor form without the pressure of forest competition to the sides.
High pruning will be needed with most trees to ensure a straight and knot-free bole of 6 m (20 ft); this raises the tree canopy and allows more light to reach the ground.
The straightest growing deciduous trees without forest shade pressure are those which are most light-demanding. When planting these, stock should be used which has been grown from seed collected from high-quality trees or seed orchards. Suitable species for Britain include:
· Ash (Fraxinus excelsior)
· Cherry (Prunus avium)
· Sycamore (Acer pseudoplatanus)
· Sweet chestnut (Castanea sativa)
In addition, straight-growing clones (varieties) of several species have been bred and are becoming available for planting. These species include:
· Hybrid poplars (Populus spp.) eg. Boelare, Beaupré
· Cherry (Prunus avium) - now used in France and Italy
· Black locust (Robinia pseudoacacia) - widely used in E.Europe
· Cricket bat willow (Salix alba ‘Caerulea’ )
Several species of coniferous tree can also be used, some producing timber of good quality. When using evergreen species, alley widths should generally be wider to compensate for the extra shading. Suitable conifers for Britain include:
· Douglas fir (Pseudotsuga menziesii) (some windthrow risk)
· Larch (Larix decidua, L.eurolepis, L.kaempferi)
· Lawson’s cypress (Chamaecyparis lawsoniana)
· Pines (Corsican, lodgepole, radiata, Scots) (Pinus nigra maritima, P.contorta, P.radiata, P.sylvestris )
· Coast redwood (Sequioa sempervirens)
· Western red cedar (Thuja plicata)
Trees destined for fuelwood or estate use need not have such good form or value, but should still be fast growing (especially for silvopasture, so trees rise above animals quickly) and may be chosen from a wider range of species including those below. Of these, black locust has very durable timber. Those species which coppice or pollard well can be used to provide sustainable fuelwood production.
· Italian, black and red alder (Alnus cordata, A.glutinosa & A.rubra - nitrogen-fixers) - can be pollarded
· Birch (Betula spp.)
· Black walnut (Juglans nigra) - coppice or pollard
· Black locust (Robinia pseudoacacia, a nitrogen-fixer) - coppice or pollard
· Sweet chestnut (Castanea sativa) - coppice or pollard
All the above species, and also less light-demanding species (eg. oaks, Quercus spp.), can benefit from the use of rows of nurse trees as illustrated on page 4. With the choice of a nurse species which grows at the same rate as the crop species, a straight form can be greatly encouraged; once the crop tree has a straight bole of the required length (usually 3-6m, 10-20 ft), the nurse trees are thinned and removed (some may be economically usable, eg. as cut Christmas trees). Some possible combinations are:
Nurse species Crop species
Sycamore, Black alder, Red alder, Sweet chestnut, Ash,
Oak
European larch, Norway spruce, Corsican pine,
Scots pine
Italian alder, Lawson’s cypress, Larches, Norway
Sycamore, Beech, Sweet chestnut,
spruce, Lodgepole pine, Radiata pine, Scots pine,
Black walnut
Cherry, Coast redwood, Western red cedar
Italian alder, Larches, Hybrid poplars, Douglas fir,
Cherry, Black locust
Lodgepole pine, Radiata pine, Coast redwood,
Western red cedar
Back to silvoarable Back to silvopasture