The use of mixtures as the basis for setting out plantings is most commonly encountered in amenity or landscape settings as the basis for naturalistic native woodland planting. In particular in the UK, mixture-based techniques have been developed in recent decades for extensive new naturalistic ‘community woodlands’ on the urban fringe (Hodge 1995) and for new farm woodlands on surplus agricultural land. These woodlands are created using young trees (generally two-year-old ‘transplants’), planted relatively closely to achieve quick canopy closure. Because planting has to be carried out simply and efficiently, detailed planting plans are rarely used. Instead, written specifications are followed that give the contractor all the necessary information to obtain the plants, lay them out and get them planted. At its most basic level, this information includes:
– plan showing the area the mix is to fill
– percentage composition of the mix—what proportion of the total number of plants does
each species or cultivar make up?
– the size of each plant
– planting density, i. e. the number of plants per m-2, or the distance between each plant
– group sizes—approximately how many individuals of each species or cultivar are to be
planted together to form groups or clumps
– planting method, i. e. notch or pit planting.
In most situations it will be left to the contractor to randomly arrange groups of each species within the total planting area—rarely will the position of each group be shown on a plan. However, there may be specific instructions regarding the placing of certain species that, for example, may be congregated close to the edge of a plantation or around paths or entrances. In any given scheme there may be a range of mixes, the number of which will vary according to the complexity of the scheme, for example woodland-core mixes and woodland-edge mixes, edge mixes that respond to different aspects, or mixes of different species composition that respond to differences in soil type or aesthetic outcome. The main point here, however, is that drafting these planting plans is relatively quick and, importantly, the laying out and planting can be done through a series of instructions that do not require advanced horticultural knowledge to implement.
Within this model it is possible to have varying degrees of specificity in the placing of individuals and groups. Certain trees may be located individually if, for example, large material (standards or larger) are included among a mass planting of small material to give immediate structure. Again, larger material may be included as more formal elements along paths or edges. Perhaps ornamental species may be included at specific points in predominantly native plantings to produce enhanced aesthetic effects. Plant selection generally in these plantings is made on an ecological or habitat basis, choosing common native species that are suited to the site conditions.