Species for Woodland Planting

When choosing the species for your new woodland you should not try to recreate the woodland that may have existed on that site sometime in the past. Neither should you limit yourself to those species which occur in the immediate neighbourhood. You will be growing a "future natural" woodland, so include all those species that you might find in your woodland in the future.

Certain species of tree may be removed in the future but (apart from some replacements the year after planting) further tree species cannot easily be added to the woodland. Most native broadleaved trees can grow in a wide range of sites when planted in single species groups. It is only when they are planted as an intimate mixture that some species show an advantage over others. Planting the widest range of trees and shrubs that are suitable for the site will allow natural selection and management to determine how the wood develops. This is the only way to grow a truly resilient wood.

An old woodland site would have a particular range of tree species that reflects its past history and management. Often this means that they have quite a narrow range of species, but their value lies in their history and it would be unwise to lose this connection to the past by adding extra species to an old woodland site. By contrast, a new woodland is a clean slate and an opportunity to design a varied and rich woodland ecosystem.

A woodland is not just about the canopy; there are two other important elements that must be incorporated into the design stage of any woodland planting scheme. These are the understorey and the woodland edge.

The leaves of the understorey trees soak up the light that penetrates through from the canopy above. This keeps the trunks of the canopy trees in the shade making them grow tall and straight. The understorey is a sheltered woodland habitat with its own ecosystem. Many bird species spend their time in the understorey of a woodland, seldom venturing into the canopy above. A good percentage of understorey trees will help to shade out weeds in the new woodland so that by year 20 or so the woodland floor is clear and ready for establishing a woodland flora.

I would recommend 30% understorey trees and 70% canopy trees. The canopy trees will compete with each other for light, some will be unable to cope with the competition and die, others will be thinned out by woodland management to make room for more desired specimens. Understorey trees will generally not be thinned but they may be pollarded or coppiced to keep them in the understorey. After several years of management the ratio of canopy to understorey trees will approach 50:50.

Woodland edge species of trees and shrubs should be planted as a band about 5m wide (2 rows at 2.5m spacing) around all new woodlands. Because they are growing in full sunlight they will have an abundance of flowers and fruits, making them excellent for wildlife. Shrubs provide nesting sites for woodland birds and shelter the interior of the wood from uncomfortable winds. On larger planting sites the woodland edge trees and shrubs can be planted along ride sides deep into the heart of a wood.

Canopy trees. I always start with oak, pedunculate oak on neutral soils and sessile oak on acid soils. At present planting ash is not grant aided, but it can be grown successfully using disease tolerant stock planted in an intimate mixture with other species. See the blog on Managing Chalara.

Lime, smooth-leaved elm, hornbeam, sweet chestnut, Norway maple and sycamore all make fine trees in a woodland. Alder and birch are pioneer species. They are fast growing and cast little shade. They shelter other trees from the wind and encourage them to grow tall and straight.

Poplars and willows are generally too vigorous for a mixed woodland; they will crowd out all surrounding trees. But they do support a lot of insect life, second only to oak. You could plant a small amount of aspen, a native poplar, and grey willow which grows less vigorously than the similar goat willow.

Wild cherry, wild pear and wild service can all make large trees in a woodland and are particularly prized for their timber value. They need plenty of light to grow to their full potential so be prepared to "halo thin".

Beech grows well but is slow. It can survive quite dense shade for several years before taking advantage of an opening in the canopy.

Some North American trees such as red oak and black walnut grow well in UK conditions, but you should always think of a positive reason for choosing each species. A tree might be chosen because it produces valuable timber or it fills a particular ecological niche, or even because it looks particularly beautiful at a certain time of year. Don’t choose a tree simply because it will grow well.

Britain has a mild temperate climate. Many exotic species grow well in Britain if planted in an arboretum. But the same species will often struggle when planted in a woodland where they have to find their own ecological niche in the face of competition from native trees that have evolved for millennia to fit those niches.

Many of our native species have adapted over the past few thousand years to a more open landscape where it is an advantage to grow slowly and more branchy to cope with high herbivore pressure. The same species growing in the dense forests of Central Europe grow taller, faster and straighter because the bigger threat to their survival is the competition for sunlight from other trees, not herbivores. Perhaps we should be using seed from the forests of Central Europe to grow timber quality maple, lime, oak and others in our new British woodlands.

Understorey trees. These should be planted throughout the wood to provide the benefits described above. Trees could include crab apple, wych elm, woodland hawthorn, hornbeam, field maple, hazel, yew and, on lighter soils, rowan and holly.

Woodland edge. This is where the choice is widest. Shrubs such as guelder rose, dogwood, spindle, hazel, and wild privet will provide flowers, berries and autumn colour. Why not take the opportunity to plant some fruiting cherries and plums along the woodland edge where they will be accessible to pick? If you don’t pick them, then all the more for the wildlife.