A choice first needs to be made concerning the planting of native, naturalised or introduced trees. Factors which need to be taken into account include the purpose of planting, the type of habitat you wish to create, and the preferences of the local community and those responsible for the planting.
Planting trees of local genotype requires propagating planting stock from seed or cuttings from local trees, which are thought to be of semi-natural origin. Some ecologists consider this important for maintaining the local variations found within species. A problem is that many existing woodlands, hedges and individual trees were themselves planted, some many centuries ago, and the origin of that planting stock is not known. Propagation from local stock is a useful enterprise, but it may not be valid in ecological terms.
There is also the fact that urbanisation has changed the climate, soil conditions, ground water levels and other factors affecting tree growth, so that trees which were in the past matched to the local conditions may no longer be suitable. Trying to recreate a native woodland type in an urban area may not only be difficult in practical terms, but may not be appropriate for the needs of the community.
Native woodlands
The following section gives details for selecting species and mixes where the aim is to create a woodland which is as close as possible to the natural type of woodland which would once have existed in the area. This aim may be appropriate for larger areas of woodland on the outskirts of urban areas.
The national Vegetation Classification (NVC) describes 19 major types of woodland, characterised by distinctive mixtures of trees, shrubs and ground flora. See Creating New Native Woodlands, Forestry Commission (1994) for full details. Each type is limited to a particular climatic zone and certain types of soil, and represents the kind of climax vegetation that could develop if succession was allowed to take its full course. Seven different types are described below, covering the main urban areas of Britain, which are all lowland. The remaining types are either upland or of very limited distribution.
Northern Ireland has its own types of woodland, which differ from the British woodlands described below. Several British species are not native to northern Ireland, including beech, lime, field maple and hornbeam. Beech is possibly absent because of the lack of chalk downland, its typical habitat. Lime may be absent because the climate is not normally warm enough to produce viable seed. Another factor is that some species did not spread as far as Ireland before the land bridges were breached after the Ice Age. Species widely distributed through northern Ireland include alder, ash, hazel, holly, oak and rowan. As in the rest of the British Isles, very little native woodland remains. For further details see Our Trees, Conservation Volunteers Northern Ireland (1997).
The presence of the ‘optimal precursor vegetation’ given below for each woodland type would indicate the site’s suitability for supporting that type of woodland. However, any existing vegetation may be considered of sufficient value as it is, that woodland planting is not advisable. Most of any precursor species would survive within a new woodland and become the basis of the woodland flora, but would be suppressed.
1 Lowland mixed broadleaved woodland with dog’s mercury
This occurs over limestones, calcareous shales and clays, and lime rich deposits such as boulder clay, which develop soils of brown calcareous earths, basic brown earths and base-rich ground-water gleys. Typical terrain includes gently undulating basins, vales and low plateaux across central and eastern England, and limestone scarps in the north and west. This is one of the most diverse woodland types in Britain with a great variety of composition and structure. Light demanding shrubs thrive along margins, and in any man-made clearings and rides within the wood.
The optimal precursor vegetation is dry or damp rank grassland with tufted hair-grass, false oat grass, Yorkshire fog, nettle, creeping and spear thistle, with bramble and ivy.
2 Lowland mixed broadleaved woodland with bluebell
This occurs over non-calcareous sedimentary shales and clays, granites and lime-poor deposits such as clay with flints, which give rise to brown earths, moderately acidic brown earths and base-poor ground-water gleys. Typical terrain includes gently undulating basins, vales and low plateaux across central and eastern England, valley bottoms and gently sloping sides towards the north and west. This type of woodland is less diverse than (1) above, but still with plenty of variety amongst the minor trees and shrubs.
The optimal precursor vegetation is rank grassland with false oat grass, Yorkshire fog, cock’s foot, rosebay willowherb, creeping and spear thistle, with bramble, gorse, broom and bracken.
3 Lowland oak-birch woodland with bilberry.
This occurs over sedimentary sandstones, grits, sands and gravels, and pervious lime-poor superficial deposits, which give rise to acid sandy soils, acidic brown earths and podzols. Typical terrain includes dip slopes and plateaux, free-draining basins and terraces in the south and east, and valley sides and scarps towards the north and west. The number of shrub and herb species is low, although a rich flora of mosses and lichens can develop.
The optimal precursor vegetation is grassland and heath with heather, bilberry, bell heather, gorse, wavy hair grass, sheep’s fescue and common bent.
4 Beech-ash woodland with dog’s mercury.
This occurs over chalk and limestone, which gives rise to rendzinas and brown calcareous earths. Typical terrain are scarps and steeply sloping ground on the limestone hills of the south east. Beech casts a dense shade, and the rich associated flora develops only along the edge or within rides and clearings within the wood.
The optimal precursor vegetation is rank grassland with false oat grass, tor grass, upright brome, false brome and marjoram.
5 Beech-oak woodland with bramble.
This occurs on non-calcareous sedimentary shales and clays, and lime-poor superficial deposits such as clay with flints, which give rise to typical brown earths. Typical terrain includes dip slopes and plateaux, often drift-covered, on the low hills of southern Britain. Beech makes its best growth in these areas, making lofty canopies with holly and yew below, and little or no ground flora.
The optimal precursor vegetation is rank grassland with false oat grass, Yorkshire fog, cock’s foot and creeping soft-grass, or scrub of bramble, gorse and bracken.
6 Beech-oak woodland with wavy hair-grass.
This occurs over sedimentary sandstones, grits, sands and gravels, and pervious, lime-free superficial deposits. Typical terrain includes dip slopes and plateaux, often drift-covered, on the low hills of southern Britain, and free draining basins between. The acidic soils do not support great diversity, but the heath flora at the edges and in glades can be attractive. Pine and other conifers are likely to spread into open areas.
Optimal precursor vegetation is grassland and heath with heather, bell-heather, gorse, bilberry and wavy hair-grass.
7 Alder woodland.
This occurs over young alluvium and enriched fen peats alongside mature river valleys and edges of open water, and in floodplains and basin mires. In younger stands, almond, osier and purple willow predominate, with mature stands of crack willow and alder closing over and allowing only nettle, willowherb and goosegrass to flourish. Wide spacing of trees is needed to develop a richer associated flora.
Optimal precursor vegetation are areas of tall herb or grassy fen with common reed, stinging nettle, goosegrass, great willowherb and bittersweet.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | ||
|---|---|---|---|---|---|---|---|---|
| TREES | ||||||||
| Pedunculate oak | Quercus robur | M | M | M | m | M | M | m |
| Sessile oak | Quercus petraea | M(nw) | M(nw) | M(nw) | m(l) | m(l) | ||
| Ash | Fraxinus excelsior | M | m(nw) | M | m | m | ||
| Silver birch | Betula pendula | m | M | M | m | m | m | |
| Downy birch | Betula pubescens | m | m | M(l) | m | |||
| Wych elm | Ulmus glabra | M(nw) | m(nw) | |||||
| Field maple | Acer campestre | M(se) | m | |||||
| Beech | Fagus sylvatica | M | M | M | ||||
| Small leaved lime | Tilia cordata | m | m | m | m | m | ||
| Large leaved lime | Tilia platyphyllos | m | ||||||
| Holly | Ilex aquifolium | m | m | m | m | M | M | m |
| Crab apple | Malus sylvestris | m | m | |||||
| Rowan | Sorbus aucuparia | m | m | m | m | m | ||
| Aspen | Populus tremula | m | m(l) | m(l) | ||||
| Alder | Alnus glutinosa | M | ||||||
| Crack willow | Salix fragilis | M | ||||||
| White willow | Salix alba | M | ||||||
| Gean/wild cherry | Prunus avium | m(l) | m(l) | m | ||||
| Whitebeam | Sorbus aria | m(l) | m(l) | m | ||||
| Hornbeam | Carpinus betulus | m(se) | m(se) | m | ||||
| Yew | Taxus baccata | m | m | m | ||||
| SHRUBS | ||||||||
| Hazel | Corylus avellana | M | M | M | m | |||
| Hawthorn | Crataegus monogyna | M | M | M | m | m | ||
| Blackthorn | Prunus spinosa | m | m | m | ||||
| Elder | Sambucus nigra | m | m | m(l) | m | m | M | |
| Guelder rose | Viburnum opulus | m | m | m | m | |||
| Wild privet | Ligustrum vulgare | m | m | m | ||||
| Dogwood | Cornus sanguinea | m(se) | m | |||||
| Spindle | Euonymus europaeus | m(se) | m | |||||
| Wayfaring tree | Viburnum lantana | m(se) | m(se) | m | ||||
| Juniper | Juniperus communis | m | ||||||
| Purging blackthorn | Rhamnus carthartica | m(se) | m(l) | |||||
| Alder buckthorn | Rhamnus frangula | m(l) | m | m(l) | ||||
| Gorse | Ulex europeaus | m | m | |||||
| Broom | Cytisus scoparius | m | ||||||
| Grey willow | Salix cinerea | m | m | m | m | |||
| Goat willow | Salix caprea | m | ||||||
| Almond willow | Salix triandra | m | ||||||
| Osier willow | Salix viminalis | m | ||||||
| Purple willow | Salix purpurea | m |
Non-native woodlands
The native distribution of species outlined above has been greatly altered by man over the centuries. Species not native to the locality, and introduced species, have been widely planted for economic reasons or because people found them attractive. Many people would see this spread of species as a benefit to the landscape. Beech is too good a tree to be confined to the south and east, and it is not surprising that it has been widely planted throughout Britain for its timber, for shelter at altitude, and for its beauty. It regenerates naturally throughout Britain, and it is not known why its natural distribution was so limited. Similarly, the Scots pine, though it can be a problem on heathlands, is a magnificent high-canopied evergreen which has blended well into many landscapes outside its homeland in the uplands of Scotland. Confining choice of species to only those known to be locally native may not be a sensible objective for amenity woodlands and those on altered substrates. Trees with a high, light canopy are good for amenity woodlands, and a clump of trees that are noticeably different in colour, texture or form can add character and provide a sense of place in an otherwise homogenous woodland. On altered substrates, on very exposed sites, or where vandalism is a problem, robust, fast-growing species may be needed as pioneers in establishing trees.
Urban areas also support many plant species that have spread of their own accord following accidental or deliberate introduction into the British Isles. In their pioneer stages, natural (i.e. unplanted, naturally seeded) woodlands on urban sites contain many species recently established in the wild, which rarely turn up in rural situations. It is probable that in the later stages of their succession, these woodlands will, if left unmanaged, converge on one of the rural types described above.
Stands of mature, single species woodland are not natural, and are of less benefit for wildlife than more varied woodlands, but they form some of the favourite woodscapes for amenity use. Beech woods, stands of Scots pine or silver birch are wonderful to look at and inviting to walk through. Regularly managed coppice of hazel, sweet chestnut, lime or even sycamore have a similar attraction. Single species planting may also be easier to manage when planting small patches of woodland, so that all grow up together. This avoids the problem of differential rates of growth from a mix of species which, in a small woodland, may result in only a few individual trees thriving.
The choice of species comes down to what is possible, what is appropriate for the area, and what local people want. The feeling of being in a semi-natural woodland would be spoiled by the presence of introduced species. However, where planting is adjacent to housing areas, an open meadow-woodland or parkland may be preferred for its appearance and its potential use. In this kind of setting, some introduced species or ornamental forms of native species may be appropriate.
Streets and parks in urban areas are characterised by particular introduced species chosen for their tolerance of pollution, attractive foliage and regular, stately proportions that enhance the built landscape. These street and parkland trees include such favourites as London plane, horse chestnut, common lime, copper beech and tulip tree. Smaller trees include ornamental crab-apples, flowering cherries, birches and other ‘garden’ trees. These are not trees to plant en masse in woodlands, but which should not be omitted altogether from urban green space, not least because many people like them. native assemblages of trees with their understorey are too ‘wild’ for many people, and unsuitable for some amenity use. note that ornamental trees are generally sold as 1.5-1.8m plants, pot-grown or bare root, and are very much more expensive and slower to establish than transplants.
Productive woodlands
Trees can be planted for the timber and fruit they produce. This can have the advantage of encouraging care and management of the woods, as well as producing materials or income which can be used for further management. Managed, productive woods tend to be of less value for wildlife than less managed woods, but can fit well with the desire for urban woodlands to be fairly ‘open’, and be regularly visited by woodland workers, thus encouraging use by others.
Traditional coppice products
Hazel, sweet chestnut and oak coppice woodlands produce useful materials for hurdle making, fencing, and garden uses such as bean poles and pea sticks. Mutual benefit can be gained by establishing a small area of coppice adjacent to allotments or gardens. ‘Green’ woodworking, or working with freshly-cut wood, is usually carried out in the woodland itself. Coppice products can be cut from trees of about seven years and older, or coppicing can be started or resumed in existing woodlands. The wood is divided into areas or ‘coupes’, which are cut in rotation. Coppice management is an ancient method of harvesting trees, used because it could be achieved with simple tools to produce small-diameter poles which were easily worked. For the same reasons, coppice management is a good form of woodland management for voluntary groups, as it can be safely undertaken by trained amateurs using bowsaws, loppers and billhooks.
For further details see Green Woodwork,Abbott, Mike (1989), Traditional Woodland Crafts, Tabor, Raymond (1994), and Woodlands – Coppicing.
Woodchips, firewood and charcoal
Woodchips can be produced from any timber, from thin prunings to large-diameter timber. Woodchips can be used for fuel, in special multi-fuel burners, for mulch in woodlands and gardens, and for path and playground surfacing. Groups managing large areas of woodland will find it worth purchasing their own woodchipper, together with the necessary training to operate it. Other groups may need to hire a machine and operator as needed, or take material to a community or council-operated woodchipping facility.
Firewood can be produced from small or large diameter timber. Small-diameter timber is best used on wood- burning stoves, rather than open fires. Firewood is probably only worth producing if you have a ready market to hand, as marketing or transport is likely to absorb any profit you might make.
Having nearly died out in this country, the skills of charcoal burning are undergoing a great revival. This is due to the demand for barbecue fuel being met by managers of small woods. ‘Environmentally friendly’, locally-produced charcoal from native species in managed woods is beginning to challenge supplies from abroad, where the source of the charcoal is not always known. In suitable woods, a charcoal burner may pay to come and harvest the timber and operate a mobile kiln. TCV and other conservation groups are active in operating kilns in some areas of the country.
High value timber
Growing trees for timber is a long-term investment, with no return before at least 70 years for hardwoods. Trees need careful pruning in the early years, and close planting to produce tall, straight trunks for maximum value. Formative pruning, involving removal of side shoots, promotes quicker height gain, and results in a clear-stemmed, high canopied tree. For the reasons of security described above, in some urban woods this type of tree growth may be preferred to a more natural branching growth with an understorey. Harvesting requires felling trees when in their prime, which is likely to be unpopular.
Fruit
Contact Common Ground for information on the planting and care of orchards for community use.
Urban squirrel populations are likely to decimate hazel and cob nuts. In ‘mast’ years, the gathering of fruit and nuts for seed can be undertaken as part of a tree nursery operation.
The traditional ‘hedgerow’ fruits of blackberries, sloes and hips, from hedgerow and woodland understorey, always attract pickers, and conkers remain an irresistible magnet for children. Horse chestnuts have recently been shown to produce a substance effective in treating sprains, validating an ancient Romany cure. Plantations of horse chestnut trees in the Uk are being planned by a pharmaceutical company. A grove of horse chestnut trees may become an asset too valuable for small boys to plunder!
