Planting with wildlife in mind:
An overview of issues concerning the sourcing and use of native plants
A Flora locale guidance note
Today, many schemes, across all the major land-based sectors, have among their objectives the creation or restoration of plant communities that have value for native wildlife. Examples include:
Plants that are established in these schemes will provide the essential building blocks upon which new areas of biological diversity can evolve - from microbes and fungi networks that are associated with plant roots and soil, to leaf and nectar feeding insects, birds, reptiles, amphibians and mammals.
With pressure continuing on existing wildlife habitats and species, and an increasing public desire to be put in touch with "the wild", this upswelling "go native" movement offers a chance to put something back. But habitat creation should not be seen as a substitute for the proper conservation of important habitats that still exist.
However, if the "go native" projects undertaken at a field or landscape scale are to make a real and significant contribution to enhancing local environments for wildlife, there are a range of issues which need to be addressed.
The importance of plant and seed sources
In fact the majority of native trees planted in the UK within the past 25 years have been sourced from overseas and do not represent the native genetic variability of trees found growing in the wild in the UK. In recent years an increasing amount of the wildflower seed used has been of British native origin, but the use of imported continental material, agricultural and amenity varieties is still commonplace. Practically all the grass seed used in the UK is sourced from abroad.
The use of introduced or translocated seed and plants may have a variety of consequences. These include:
Plantlife - the Wildplant Conservation Charity, was one of the first organisations to highlight these issues in the report Seeds of Destruction (Akeroyd, 1994). Since then has been an increasing appreciation that the origin of plants and seed is important.
However, at present, there is a dearth of scientific knowledge about the genetic variation and adaptive traits of our native plants, and whether small differences exhibited in a particular species, are important. We do know that there is adaptive variation among some species, and that physical differences in the shape or size of a flower when it is selectively bred can make it useless for native insects which take nectar from the wild forms.
A little research carried out into genetic variation among native species growing in the UK, has also found that plants of the same species growing at different locations can be quite different in their appearance, growth and behaviour. These variations have evolved over long periods and reflect adaptation to local conditions, such as climate, soil chemistry and water. For example, distinctive forms of some wildflowers have evolved where species populations have been isolated for a long time, such as on the coastal fringe, on islands and in local biogeographic regions that are well separated from other similar ones. Differences have also been identified among tree species growing at different altitudes or latitudes.
Armed with the little information we do have, it is difficult to be certain about what the best approach to sourcing planting material should be for individual species and locations. For this reason, the approach proposed by Flora locale and by the UK Forestry Commission (the only UK government agency to have, so far, attempted to have tackled this difficult subject) to sourcing planting material is based upon the precautionary principle - with emphasis on sourcing plants from similar habitats nearby, wherever possible.
A problem of definitions
One of the major problems facing anyone wanting to "create" native plant communities and use appropriate planting material, is the wide range of definitions applied to describe different seed and plant sources. Definitions for identical terms, such as "origin" and "provenance" are different, depending on whether you are talking to someone working in forestry, landscape or horticulture. To overcome this, Flora locale has produced a Specification for Native Plants.
The terms that Flora locale asks plant specifiers and suppliers to use are:
The place of native origin or native provenance should be stated (e.g. Plant of British native origin, or, Native origin: Berkshire, Plant of Hungarian native origin). The term "provenance" is otherwise meaningless, as it means "the place that a seed or plant was collected from", which could be a plant nursery.
To achieve a standardisation in the way the terms are used, plant collectors, growers, suppliers and users are invited to adopt Flora locale's Code of Practice for collectors, growers and suppliers of native flora. This also requires the source to be identified at the point of supply in particular, the place of native origin should always be given, or stated as "native origin not known").The right plant in the right place
Using the right combination of native plant species will create a framework which will promote the colonisation of a site by a diverse range of insects and other invertebrates, such as butterflies, ants and bumble bees. The native plant community is, in effect, the essential building block for re-creating and rehabilitating biodiversity in damaged landscapes. However, no one should be deluded into thinking that a pristine and wildlife-rich habitat, such as a stunning wildflower meadow, can be re-created overnight.
If the objective of a scheme is to create some kind of coherent plant community, it is not only important to select the right combination of plants, but species which will actually grow. Like plants commonly used in formal horticulture, British native plants include annuals, biennials, perennials, species which like lime-rich soil and those which do not, wetland plants which don't grow on droughty sands, and so on. In the wild, these plants form distinctive associations which reflect the nature of the soil, the water regime, geographical location and influence of management (such as sheep grazing or mowing) or interference by people, animals and other fauna. These plant associations are described in the British Plant Communities volumes (published by Cambridge University Press). A useful abbreviated synopsis is also published as British Plant Communities in Natural Associations (Christopher Betts, 1997).
Other useful references are:
Understanding the natural range of native plants is very important when selecting species to establish - both to ensure that the plants will survive and that the naturalness of remaining native plant communities in the locality is not deleteriously affected. Maps showing the national distribution of native plants (by 10 km square) can be found in the Atlas of the British Flora (soon to be revised by as the Atlas 2000). More detailed distribution maps are also available for most of the English counties, published as individual county floras. Details of these publications are available from the Botanical Society of the British Isles.
Judgements about what is the right species to plant must take into account both the ecological and landscape context of an area, as well as the scheme objectives. In some cases, this may lead to a decision to plant a native species outside its natural range but not where nature conservation is the primary objective. Some native species have already been extensively planted outside their natural range and in the wider countryside, where they are now considered to form important components of the landscape. Beech is such an example. In contrast most native wildflowers have discrete natural ranges and their distribution has, historically, not been extensively tampered with.
Bird Cherry Prunus padus is a very attractive small native tree worthy of planting in urban areas, but its natural distribution in Britain is patchy. It should not be planted in ancient woodlands and hedgerows where it had never naturally occurred in recent history (and where it could be potentially invasive and eventually distort the balance of indigenous tree and shrub species). This is an example of a native species where planting outside its natural range would be acceptable in certain "controllable" circumstances, but could pose problems to existing wild plant communities in others.The establishment of native species outside their natural range also has implications for environmental monitoring. Mapping and monitoring the distribution of native plants helps us to assess the state of the environment. Native plant introductions (putting native plants in areas where they have never occurred before) need to be recorded, so that background changes to plant distributions are not obscured. This is particularly important in the context of identifying changes in British vegetation that may be associated with global climate change. Any introductions of this sort, if they must take place, should be notified to the Botanical Recorder for the area. Details of Vice-county Recorders is available from the Botanical Society of the British Isles.
Establishing native plants, in the garden or on a larger landscape scale, can be challenging, but requires good knowledge on the ecological requirements of the plants, the place and context in which they are to be established, and the future management that will be necessary to ensure their future survival. Lack of such knowledge can lead to disappointing results, wasted effort and money, and may prejudice opinion against using wildflowers and other native species again.
For these reasons, good advice on what native species are appropriate for the planting site, should be obtained before embarking on a major scheme. This knowledge, is usually available locally either on a professional basis (e.g. from a professional ecologist with botanical skills) or via amateur botanists who belong to the Botanical Society of the British Isles. It is also available from nurseries that specialise in collecting and propagating seed of native species. Some of these also have expertise in site preparation and planting.
If you are not a plant ecologist, do not expect to learn the ecology of native plants overnight by reading a book!
Expert advice is especially important at the earliest stage of designing large landscaping projects which involve the selection and use of native species. For landscaping schemes which are predominantly using native plants, and which have as their principal purpose the creation of vegetation that is going to be of some wildlife value, the science and practice of ecology is fundamental to scheme objectives, approaches and design.Environmental responsibility and introduced species
Introduced "exotic" species have an important role in enhancing the urban environment, parks and gardens.
But there is a scant awareness about the risks posed to our native biodiversity from some introductions.
Apart from habitat destruction by man, the spread of invasive introduced species now poses probably the single greatest threat to global biodiversity. In the UK, measures now being taken to eradicate invasive plants are proving costly. At the same time, the globalisation of trade in horticulture, forestry and agriculture, means that many other wild species are piggybacking on otherwise benign imports of trees, garden and crop plants. Some of these new invaders are pests that threaten agriculture, horticulture and our native wildlife.
One extreme example is the hybrid Phytopthera disease (the progeny of two introduced species) which, by the beginning of 1999, had already destroyed around 10% of wild alder trees in southern England, and threatens to do to our alders what Dutch elm disease did to our native elms.
Horticulture, landscaping and habitat creation are potent sources of invasive exotic plant species. Examples include: