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Seeds of destruction?

Non-native wild flower seed and British floral biodiversity

Published by Plantlife - The Wild-plant Conservation Charity © 1994

 
Summary
In recent years many people in Britain have been growing native wild flowers, especially from commercially available seed-mixtures. Plantlife applauds and encourages the return of vanished, well-loved and colourful members of our flora. Nevertheless, we have been concerned for a while that a proportion of plant material on sale does not represent strictly native British wild flowers. The species are mostly correct, but few widespread species are uniform and some of the plants that are being grown in Britain are not the same as native wild flowers. This booklet, based on a report by the author commissioned by Plantlife, discusses evidence to suggest that considerable quantities of wild flower seed have been imported from abroad.
 

Wild flower seed that is not native in origin can create a number of problems:

  • Confusion as to the natural distribution of the plants in Britain.
  • Confusion of complex and ancient patterns in the landscape and creation of a facsimile of countryside.
  • Competition between native and perhaps more vigorous introduced plants of the same species.
  • Crossing between native and introduced plants, leading to erosion of native genetic variation.

We are especially concerned about the potential for crossing between native and non-native wild flowers, lest we lose unique native genetic variation, a key component of plant biodiversity, already threatened by the loss and fragmentation of habitats. It is vital that we protect Britain's biodiversity, our precious and irreplaceable resource of natural genetic variation. The British flora already contains a very large non-native element, including many familiar wild flowers and trees, but the introduction of large amounts of seed is likely to have a considerable effect on the natural ecological balance and genetic variation of native species.

This booklet presents evidence that a real problem exists and that, despite the responsible attitude of many seed suppliers, the use of introduced wild flower seed in Britain is widespread. We discuss the value of our non-native flora, but at the same time stress the importance of conserving native genetic variation. Ideas are suggested for promoting the greater use of native wild flowers, including an accreditation system for suppliers. The last section of the booklet details differences between native and non-native variants of a number of common wild flowers, many of them economically important fodder crops that may be needed in the future by plant breeders. A bibliography lists books on the use of wild flowers in gardening and landscaping.

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Introduction
Increasing numbers of people in Britain are growing native wild flowers. Many species are available in commercial seed-mixtures, which are widely marketed and promoted both by the media and by conservation bodies. Wild flowers are also available as adult plants and readily transplanted 'plugs' or tubes from more than 50 specialised suppliers. Large-scale landscaping, especially of new road-verges, cuttings and embankments, uses the bulk of available material, but a good deal is distributed through the 'wild flower' market to plant-lovers and conservationists. Plantlife has encouraged this movement to bring back Britain's vanishing heritage of well-loved and colourful wild flowers.

Nevertheless, some of us are concerned that a proportion of the material on sale, both seed and plants, may not represent strictly native British wild flowers. The species are correct, or they usually are, but few widespread species are at all uniform and many of the plants sold in Britain are just not the same as our native wild flowers. It is important that gardeners and naturalists be made aware of this and of the issues that arise through the use of non-native wild flowers. These require some serious thought and discussion.

There are more than 50 suppliers of wild flower seeds and plants in Britain, from the major seed houses to small companies that packet and market seeds independently. Individual distributors are often concerned about the indiscriminate sowing of wildflower seed. It is important that Plantlife and others continue to encourage such responsible attitudes amongst suppliers and growers, many of whom apparently take the matter of native origin very seriously.

We have not included a list of suppliers here, although a number are recommended by the Botanical Society of the British Isles in their leaflet "Growing wild flowers from seed".

Variation amongst wild flowers
Every gardener knows that plants exist as a number of 'varieties' or 'forms', which differ not only in features such as height, leaf shape and flower colour, but in vigour, hardiness and flowering time. This is also true of our wild flowers, and these differences have long interested plant geographers, geneticists and ecologists. They can often be related to factors such as habitat, climate and a history of particular land management.

A number of variants of widespread plants are distinct enough to be recognised by botanists (variant is a most useful word, because 'form' and 'variety' imply an actual name that is used by botanists). In fact many have been given scientific names - as forms, varieties and subspecies, even species. These distinct variants frequently occur as wild plants in specific geographical areas, often regions of Europe outside Britain. In many cases they are not native to this country and it is misleading to call them native wild flowers.

The nature of the problem
The available evidence suggests that a very real problem exists as a result of the use of large amounts of non-native wild flower seed. So, what exactly is wrong?

Wild flower seed that is not native in origin can have a number of consequences:

  • Confusion as to the natural distribution of the plants in Britain.
  • Confusion of complex and ancient patterns in the landscape and
  • Creation of a facsimile of countryside.
  • Competition between native and perhaps more vigorous introduced plants of the same species.
  • Crossing between native and introduced plants, leading to erosion of native genetic variation.

Two other consequences of the use of wild flower seed must be considered. Species introduced as contaminants of wild flower seed, especially that of non-native origin, have the potential to become weeds and the introduction of any new plant has to be taken seriously. One example is Bristly Hawks'-beard (Crepis setosa), a native of southern Europe that appears regularly on resown road-verges and elsewhere. There is also the matter of the rich pickings to be had from the illegal collection for sale of native plants from the wild. Plants in remote, rural areas are especially at risk, for example in north Norfolk, where there is extensive evidence for the pillage of woods for Bluebells and other wild flowers.

All these points may seem to some people to be trivial, even academic, but they need to be addressed and discussed.

The one that concerns us here is that of crossing between native and introduced plants. This is perhaps the most significant in the longer term, for we must consider above all the protection of Britain's biodiversity - our precious and irreplaceable resource of natural genetic variation. Native biodiversity is particularly at threat today because we have fewer and more fragmented habitats for wild plants. The landscape can no longer buffer any large-scale introduction of new plants or animals.

At a time of widespread public concern about the loss of biodiversity in the tropical rain forests, it would be foolish to do anything that might put at risk our own special native plants. Many have economic use or potential; some are relatives of crop plants. Who can say when they will be needed by the plant breeder?

Let us first look at the vexed question of 'native' versus 'non-native' wild flowers.

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When can a plant be called native?
Britain's altered landscape
Britain has one of the world's most modified landscapes. Truly natural habitats have almost disappeared, but our mosaic of semi-natural and artificial landscapes retains rich fragments of flora and fauna, and demonstrates vividly the history of Britain's plant and animal life and human society since the end of the Ice Age. Many of our most species-rich habitats are not strictly natural, but are complex artefacts of generations of careful, traditional management. Striking examples are the wetlands of the Norfolk Broads, the heathlands and chalk grasslands of southern England, the moorlands of northern England and Scotland, and the machair or sand-dune grasslands on the coasts of northern and western Scotland. The landscape and its biodiversity are intimately linked with our history and culture.

Surviving habitats have mostly been reduced to small islands and strips, all too frequently surrounded by uninteresting urban, industrial or intensively farmed land. This makes the species, and their variants, that survive in such pockets vulnerable to damage by insensitive management, by building and other development and as a result of invasion by, and crossing with, alien species. They will also be susceptible to factors such as climatic change, agricultural and industrial pollution, including acid rain, and other long-term, major environmental damage.

The problems of introduced species in the wild have long been recognised worldwide, especially when they invade cultivated ground or treasured stands of natural vegetation. The classic example is the damage to the Australian outback, which became covered by thousands of hectares of an introduced cactus, Prickly Pear (Opuntiaficus-indica). In Britain, large areas of land have disappeared under thickets of Japanese Knotweed (Faliopia japonica), an aggressive invader from the Himalayas and eastern Asia, once an esteemed garden plant.

The problems posed by introduced variants of indigenous species have received considerably less attention.

Our non-native flora
Many familiar plants are not actually native to Britain. They have arrived over thousands of years during various episodes of human invasion, colonisation and trade. Today, however, they are totally naturalised.

Some botanists have resisted all introductions of plant species to Britain. Others take a positive attitude to introductions, recognising that these plants can make a significant contribution to our flora. So many of our wild flowers, trees and shrubs are not native, although their origins are obscured by time. Stone Age settlers introduced well-loved cornfield weeds, such as Cornflower (Centaurea cyanus) and Corn Cockle (Agrostemma githago), both of them treasured rarities today. The same people may have introduced Beech (Fagus sylvatica), and the Romans introduced Sweet Chestnut (Castanea sativa).

Other non-native trees and shrubs have been widely planted in the recent past, to become characteristic features of the countryside, notably Horse Chestnut (Aesculus hippocastanum) from Greece and Albania, now as much a part of the English scene as church, cricket and village pub. Other trees, such as Holm Oak (Quercus ilex), well established locally in southern England, and several of the attractive Southern Beeches (Nothofagus) from temperate South America, already growing wild in the Quantock Hills of Somerset and elsewhere, will be just as familiar in time.

Fewer examples have been recorded of the deliberate introduction of individual annuals and herbaceous perennials, i.e. the plants known collectively as 'wild flowers'. However, a number of species have arrived as crop plants and have escaped into town and countryside. Many crop plants are distinct variants of native species and the crop itself may also become established in the wild. Garden plants too, especially the denizens of the traditional cottage garden, are established in the wild, not only around villages and on roadsides but also beside rivers and in woodland, adding colour and variety to our flora and landscape.

Striking examples, which have come to be regarded by most people as native wild flowers, include Himalayan Balsam or Policeman's Helmet (Impatiens glanduhfera) and several species of Monkey-flower (Mimulus), Comfrey (Symphytum) and Mullein (Verbascum). Some of these are invasive - and a few such as the notorious Giant Hogweed (Heracleum mantegazzianum) can be a menace – but they are for the most part welcome. One garden introduction in particular that has improved the landscape is the delicate, creeping Slender Speedwell (Veronica fihformis), a native of the Caucasus. In early May, grassy places and lawns shimmer with its thousands of tiny blue flowers, in part making up for grassland flowers lost through intensive agriculture.

Wild flowers in gardens and for amenity
Gardeners have always grown wild flowers. Some native wild plants, such as Mezereon (Daphne mezereon), have been pillaged for cottage gardens, but conversely have also escaped from gardens to found new populations in the countryside. Common wild flowers of the cottage garden, such as Foxglove (Digitalis purpurea) and Sweet Violet (Viola odorata) have a native distribution obscured by a history as popular garden subjects. As long ago as 1870, Victorian garden-writer, William Robinson, who so influenced the legendary Gertrude Jekyll, was encouraging wild gardening and the integration of nature and the garden.

The large-scale cultivation of wild flowers is a recent phenomenon, which seems to have begun in Holland shortly after the Second World War. There, as in Britain, the movement arose as a reaction to the loss of natural habitats in a densely populated country with intensive agriculture. The last 15 years have seen an extraordinary expansion of the wild flower seed industry in Britain, much of it following the publication in 1981 of the Nature Conservancy Council's booklet, Cicating attractive grasslands using native plant species. Conservation, wildlife gardening, the creation of new habitats and the use of wild flowers in amenity landscaping have become fashionable, promoted by the influential horticulture industry and the media.

Plantlife applauds this interest and awareness of our wild flora, but not only must we consider the many effects that our enthusiasm may be having on existing native plant communities, but also establish the source of seed and plants.

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Non-native sources of seed
The popularity of wild flowers has created a heavy demand for seed that has caused inevitable problems of supply, leading to imports from abroad. At the same time, there exists a large pool of agricultural seed, much of it non-native in origin and surplus to farmers' requirements, that can be obtained readily and cheaply by suppliers. The implications of this trade for our native flora were soon noted by some botanists and naturalists. In 1985, the well-known environmentalist Professor Chris Baines pointed out in his book, How to make a wildlife garden:

"The seed of wildflowers is increasingly easy to come by, but ... foreign stock is widespread. This can be quite a serious problem, as the foreign strain of some of our wildflowers is much more vigorous than the native type, and could well overwhelm the indigenous stock. The responsible seedhouses are very particular about this point" our italics.

Despite the good intentions of many seed suppliers and those promoting the use of wild flowers, it has become apparent that much of the seed being distributed in Britain is not of native origin. As long ago as 1969, a non-native variant of Bird's-foot Trefoil (Lotus corniculatus), apparently a native of the southern Alps, had been reported from road-verges in Denmark and other parts of northern Europe. This and non-native variants of other plants were widely sown in Britain from the early 1970s. Botanists expressed concern about possible effects on the genetic constitution of the flora, and some preliminary research was carried out on the interaction between native and non-native variants of Bird's-foot Trefoil.

In 1989, the late Dr John Dony raised the matter of introduced wild flower seed in an impassioned plea at an Annual General Meeting of the Botanical Society of the British Isles. Based on his experience of recording the flora of Bedfordshire, he stated that the deliberate use of wild flower seed, especially of foreign origin, would render pointless the task of the botanist attempting to record the distribution of native wild flowers.

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How do we know that some wild flowers are not native?
Evidence from plant form
Most plant species are variable and much of this variation can be related to habitat factors. In most cases that have been investigated, variation has been found to have at least some genetic basis: in other words, characters are 'fixed' and can be passed on to the next generation. Genetic variation in populations of plants can be observed in form, life-history, physiology and biochemistry. Modern molecular techniques have greatly aided the study of genetic variation, but the principal tool of the botanist who wishes to identify plants remains the observation of their shape, size and structure.

If you look at a site that has been sown with wild flower seed, have a closer look at some of the common species such as Bird's-foot Trefoil. Note whether or not the plants are robust, tall and erect; are the flowers the same colour as you normally see in this species? Similarly, Kidney Vetch: are plants unusually robust and erect and are the leaflets different in shape to the plant of chalk grassland? If Salad Burnet is present, and in fruit, have a look at the fruits - perhaps they are unusually warty. It is these sort of distinguishing differences between plants that attract the eye of the botanist interested in variation within species.

The botanist will then look through the various available Floras, new and old, to identify which variety, subspecies or distinct variant that he or she may have seen. The Flora should also indicate the native range of the plant. Again and again, we have found that too many wildflowers sown in Britain clearly originate in other parts of Europe. Sometimes we can be reasonably precise. It would seem that every plant of Kidney Vetch sown on roadsides in Britain belongs to a subspecies (indeed a variety of that subspecies!) that is native to the valleys of the Alps and other mountains of central Europe. Meanwhile, the native plant is now scarce over much of lowland Britain.

Evidence from life-history
An interesting feature of many widespread European plant species is that the further south they occur, the shorter their life-history. In Britain, Wild Carrot (Daticus carota) is a biennial to short-lived perennial, whereas in the Mediterranean region this species is frequently annual. Annual variants of Wild Carrot have been found on sites sown with wild flower seed as far apart as Berkshire and Galloway. This sort of evidence is very useful to demonstrate that non-native material has been used. Bulbous Buttercup (Ranunculus buibosus) has, in northern Europe, a characteristic bulbous corm or swollen stem-base. However, in southern Europe, this species lacks this feature and appears to have a shorter life-history. The southern European plant has not been reported in Britain, but a rather similar plant, the non-native annual St Martin's Buttercup (Ranunculus marginatus) has on occasion been substituted for it in seed-mixtures (see below).

Evidence from seed testing
Britain, like most nations, imports a vast quantity of seed. Data gathered over a long period by the National Seed Testing Station confirm that enormous quantities of non-native seed arrive in Britain each year. It has been estimated that in a typical year during the 1980s this country imported seed from nearly 100 different countries, representing every continent. Furthermore, at least some of this seed has been sold and distributed in wild flower seed-mixtures. It is much more difficult to identify seeds or seedlings than adult plants, but the data available from seed testing suggest that, for example, most commercially available Salad Burnet is probably not native, representing instead the more readily obtainable Fodder Burnet.

Some seed is known to have been grown on in this country from plants raised from imported seed. This material is no more British in origin than "British Sherry", even though it can legally be termed native wild flower seed.

Evidence from seed suppliers
Evidence for the use of non-native seed comes from the suppliers themselves. Many suppliers of wildflower seeds are scrupulous in their presentation of a quality product and are as concerned as we are about the widespread use of non-native seed. Some suppliers will always indicate when they are unable to provide native seed. For example, one catalogue notes the importance of different types of seed for different projects. A section on natural meadows lists mixtures from special Thames Valley sites, together with one from a planted meadow originally derived from wild-harvested seeds - but with the addition of Ox-eye Daisy, Meadow Buttercup and Fodder Bird's-foot Trefoil. Here, the fodder legume is clearly identified as a component of a wildflower seed-mixture, one which is, to quote the catalogue, "the type being considered for large scale use on motorway embankments, road verges etc."

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How widespread is the problem?
We have come across many examples of the use of non-native wild flower seed throughout Britain. We have seen them ourselves or they have been reported to us by other botanists and naturalists. Most relate to the landscaping of road-verges, cuttings and embankments, where practical and aesthetic considerations too often take precedence over conservation. Nevertheless, there is evidence that the sort of commercial seed that has been used by the Department of Transport and others is also being employed in projects where native seed would have been expected.

Examples are everywhere: from the Brixton gardener interviewed on BBC2' s Gardeners World, disappointed that the White Clover in his urban wild flower garden was "agricultural", to the robust variants of common wild flowers that can be purchased in pots at a range of horticultural outlets. One seed-mixture distributed by conservationists as part of a package to attract bumblebees contained a huge variant of Red Clover, but mercifully most of the seed of the other species included failed to germinate!

Two notable examples illustrate that even prestigious conservation projects are at risk from non-native seed.

Magog Trust, Cambridge, 1991-2
In 1989 the Magog Trust purchased land on the Gog Magog Hills just outside Cambridge in order to establish new chalk grassland on arable land. This is to be managed, together with adjacent existing and replanted woodland, as a public amenity. Money was raised by public donation and by a grant under the auspices of the 'set-aside' schemes for farmland. Experts were consulted, seed was chosen with care from reputable seed-merchants, and the land was ploughed and sown with a grass and wild flower seed-mixture in the spring of 1991. By that autumn, however, a number of botanists had noted a flora of unusual native and non-native species on the site. A detailed assessment of the flora was possible because the site had been regularly visited by botanists since the 19th century and a full inventory of the flora had been made in 1987 as part of a recording survey for the Botanical Society of the British Isles. Several of the most interesting species were undoubtedly native and had long been reported from the site, whereas others were certainly contaminants or deliberate components of the seed-mixture.

These included Cornflower (Centaurea cyanus), many of horticultural origin, with pinkish-purple flowers, Corn Marigold (Chrysanthemum segetum), rarely found on the chalk, a southern European subspecies of Hawkweed Oxtongue (Picris hieracioides), Fodder Burnet (Sanguisorba minor subsp. muricata) instead of the native Salad Burnet (S. minor subsp. minor, which grows nearby, and agricultural Red Clover (Tnfolium pratense var. sativum).

The most astonishing discovery at this site was St Martin's Buttercup (Ranunculus marginatus var. marginatus), closely related to the native Hairy Buttercup (R. sardous). This species is native to a large area from Albania to Iran, and has previously been reported from Britain only as a rare casual. R. marginaflis var. tracliycarpus, with warty rather than smooth fruits, persisted as a weed for many years on St Martin's in the Isles of Scilly. This obscure plant has recently turned up at another site, this time in the north of England, that had been landscaped with wildflower seed. In both cases it was undoubtedly the 'buttercup' or 'bulbous buttercup' included in the seed-mixture.

Garden Festival Wales, Ebbw Vale, 1992
A Wild Flower Meadow was one of many features at the Festival laid out to illustrate the interaction between landscape, conservation and wildlife. A tall, mixed grassland had been established on a steep slope on reclaimed colliery spoil. Here and there were patches of individual plants, such as Viper's Bugloss (Edlium vulgare) and Large-flowered Evening-primrose (Oenothera biennis), set out to give bold splashes of colour. Apart from the Evening-primrose, a well-established member of our flora that came originally from America, all the species were native to Britain. The grassland was an excellent example of the reclamation of derelict land using native species, but to call it a 'wild flower meadow' was misleading.

Perhaps the most distinctive plant in the sward was Flattened Meadow-grass (Poa compressa), used with Rye-grass, (Lolium perenne) as the basis of the sward. Flattened Meadow-grass is, however, a rather scarce plant over much of Wales. The most abundant and prominent plant was Fodder Bird's-foot Trefoil (Lotus corniculatus var. sativus), with clumps of weakly erect stems 40-60 cm. An observant visitor, overheard as she walked past, remarked: "That doesn't look like ordinary Bird's-foot Trefoil"! No it did not, but a few hundred metres away, adjacent to the Festival Farm, was an attractive, established pasture of mixed grasses, native Bird's-foot Trefoil, Red Clover and Self-heal. Here one could observe that the native plant is much neater and more prostrate in habit. Also, in the main body of the Festival itself were a few square metres of wildflower-rich grassland planted by means of turves, as part of the National Trust's landscape exhibit. This grassy patch contained native variants of both Bird's-foot Trefoil and Oxeye Daisy.

However, of the three clovers used in the Wild Flower Meadow, Alsike, Red and White, only the Red Clover was the gross forage variant (Trifolium pratense var. sativum). A handsome variant of Hardheads or Knapweed (Centaurea nigra), with long ray florets, that was present does not usually occur in Wales. The Oxeye Daisy used was the robust garden hybrid, Leucanthemun x superbum. More unusual constituents of the sward were plants of Yellow Chamomile (Anthemis tinctoria) and one of the long-headed species. Neither plant is a native but both are widespread in central Europe. They are likely to have been contaminants in the seed-mixture, supporting the suspicion that at least some of the seed had come from central or southern central Europe. The two members of staff at the nearby Countryside Centre exhibit were surprised, and not a little disappointed, when I discussed the meadow with them - for they had assumed that it represented a native sward - but details of the seed sources requested at the Garden Festival office were never forwarded. Clearly, a large amount of non-native wildflower seed is being used in Britain, even for conservation projects. Clovers and other peaflowers are a particular problem because they are readily available as agricultural seed. These form an important group because their native populations represent a genetic resource of inestimable potential value. Not only are agricultural clovers frequently recommended by experts for land restoration and landscaping, but considerable sums of money are currently available to bodies such as the Department of Transport for landscape planting.

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Trouble in store? Wild flowers on 'set-aside' land
We may see further expansion of the wild flower seed market with the increase in 'set-aside' agricultural land. Modern agriculture was responsible for most of the destruction of our wild flowers, especially in old grasslands. Ironically, agricultural surpluses have now forced EC governments to take land out of production temporarily or permanently. There are problems for the re-establishment of semi-natural plant communities. It is not just botanists who are concerned about some of the effects of 'set-aside' policies, for there is evidence that infestations of perennial weeds can build up on this fallow land.

Several commentators have suggested that wildflower seed might be used to beautify otherwise sterile landscapes, as well as providing food for insects such as butterflies and bumblebees, and one alternative to set-aside might be the creation of broad, wildlife-rich field margins. This has been tried locally on an experimental scale and is recommended by the Game Conservancy and others. Wildflowers sown on field margins have been shown to slow the rate of growth of noxious field weeds. However, this sort of project on a large scale might cause considerable problems for the long-term interpretation of our flora and trivialise our landscape and floral heritage.

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Learning from others
Our international obligations
We in Britain must develop a long-term policy for the protection of our native biodiversity. Indeed, since we have signed the Biodiversity Convention, proposed at the Earth Summit in Rio de Janeiro in June 1992, we are obliged to do so under the terms of international agreement. There has been some public debate on the status of our tree flora, notably concerning an EC decision to discourage the planting of native oaks. The conservation and restoration of native Scots Pine (Pinus sylvestris var. scotica) forests in the highlands has been exemplary. However, the biodiversity represented by our native wild flowers has largely been ignored.

Can we learn from other European countries?
In France, rigorous measures are being applied to ensure the genetic conservation of threatened wild plants, an approach that could be extended to cover all native plants, especially in a small and overcrowded island such as our own, where even formerly common wild flowers are restricted to a few surviving pockets.

In Scandinavia, the Nordic Council of Ministers has established a Nordic Gene Bank to conserve both native and introduced genetic resources in Scandinavia and Iceland, especially populations of native forage grasses and clovers. It is worth considering the Council of Europe's Recommendation on the introduction of non-native species, adopted by their Committee of Ministers in June 1984, that the governments of member states:

"prohibit the introduction of non-native species into the natural environment", except where a study to evaluate the possible consequences of such introduction has been carried out; and that member states "take the necessary steps to prevent as far as possible the accidental introduction of non-native species".

We are not always dealing with distinct species when we consider non-native wild flowers, but surely the principles should be the same?

The problem of alien versus native variants of species in our flora will become even more significant when genetically manipulated organisms are released into the wild. Almost no thought has been given to this issue in Britain, although in Holland a report has been prepared by geneticists and field botanists on the possible impact on the native flora of gene-flow from cultivated plants. In the U.S.A., where there is a long tradition of seeding road-verges with native wild flowers (especially each State's official flower), there is more discussion of 'restoration ecology' and the whole approach to wild flowers is more sophisticated, with discussion of the practical and aesthetic issues.

Are we just too haphazard, whimsical and irresponsible in Britain?

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Some constructive ways forward
Restoration of traditionally managed grassland
Studies of the natural or semi-natural restoration of species-rich meadow from former intensively cultivated land provide hope for future schemes. A study in Sweden, on the Baltic island of Oland, indicated that many meadow species reappeared under a mowing regime on a former arable field within three years of the cessation of cultivation. In Britain, a field experiment at Somerford Mead near Oxford by Dr Alison McDonald showed that the reseeding of arable land that had formerly been meadowland, using seeds harvested from adjacent ancient meadows, produced within three years an approximation of species-rich grassland. At least one plant present in the new meadow, Knapweed or Hardheads (Centaurea nigra), was a distinctive, early-flowering variant that grows only in meadows.

It is essential that native seed of local provenance be used in this sort of project, which cannot be achieved by the use of a standard commercial seed-mixture! All over Britain there are surviving pockets of ancient grassland and other plant communities that can be carefully conserved, restored and expanded.

Suppliers show the way
Many suppliers of wild flower seeds have a most responsible attitude to their product. For example, one respected supplier of garden herbs and wild flower seeds offers advice in their catalogue on how to sow wild flower seed, together with a request that seed is not to be scattered in the countryside. Instead they recommend that any conservation seeding outside the garden is carried out "in close association with your County Wildlife Trusts or the Nature Conservation Agencies". They also note that "it would be quite inappropriate to establish many of these species in the countryside far from their natural habitats".

It is important that all of us, public and private sector conservation organisations, seed suppliers, botanists, naturalists and the many users of wild flower seed come together to discuss these issues. A step in this direction is the Wild flower Seeds Working Group.

The Wild Flower Seeds Working Group
The Wild Flower Seeds Working Group was set up in the spring of 1993 to look into the whole matter of introduced wild flower seed. The group brings together representatives from Plantlife, the Botanical Society of the British Isles, the RSNC Wildlife Trusts Partnership, English Nature, the Joint Nature Conservation Committee, NIAB's Official Seed Testing Station and from the wild flower seed trade.

Discussion has centred on the creation of a national seed-bank of widespread species, with collections included from all parts of Britain. Eventually the Wild Flower Seeds Working Group would like to see an accreditation system for suppliers who distribute native seed. These measures would go some way towards limiting the actual and potential damage to Britain's biodiversity that the present unrestricted use of seed is creating.

In this way, we shall be able to encourage the greater use of native wild flower seed, to bring back the floral carpets that once brightened our landscape. Any work of restoration, be it a painting, a building or a habitat, needs careful thought and discussion. Let us all consider the implications of the quality of wild flower seed and do our best to conserve our most precious, beautiful and irreplaceable natural resource, our biodiversity.

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Non-native wild flowers to watch
Non-native wild flowers are rarely easy for the non-specialist to identify in the field. However, some non-native variants of common species can be spotted at a glance. Notes on some of these are given below.

It is probably significant that many non-native wild flowers, especially peaflowers or legumes, are readily available from agricultural suppliers. Their frequently tall, erect habit reveals their a history of selection as fodder crops, since it makes them easier to cut, either by scythe or machinery. Few of them, apart from Red and White Clover, continue to be grown as fodder crops in Britain, although they are still grown in other parts of Europe and elsewhere.

Red Clover (Trifolium pratense)
Wild flower plantings frequently include a commercially available agricultural clover that is widespread in cultivation. This plant (var. sativum) can be recognised by the tall, erect stems and large clusters of pale pink flowers, whereas the native plant of grassland is more slender, with prostrate to ascending stems and small heads of deep pink flowers. This or a similar plant can still be seen in the countryside in surviving fragments of semi-natural grassland, notably churchyards. It is as characteristic a plant of old meadows as cowslips, hay-rattles and orchids.

White or Dutch Clover (Trifolium repens)
Native populations of this ubiquitous and remarkably variable agricultural clover would be hard to find. Nevertheless, many amenity plantings contain entirely unsuitable agricultural plants, which are enormous, with massive leaflets and tall, erect stems bearing large heads of flowers.

Other clovers
Alsike Clover (Trifolium hybridum) tends to be robust, but some amenity plantings are of astonishingly gross, erect, hollow-stemmed plants. Lesser Trefoil (Tnfolium dubium), known to farmers as Suckling Clover, is usually a delicate plant of dry banks and open grassland. Much more robust plants, with long stems and larger heads of flowers, are appearing increasingly on road-verges and elsewhere.

Black Medick (Medicago lupulina)
At least two non-native variants of this species are sown as wild flowers, one a robust, prostrate to ascending plant that was formerly grown in Britain as a fodder crop, together with another, less hairy fodder plant with larger leaves, probably from south-eastern Europe. The native plant of grassland is more prostrate and often hairy. A compact, often somewhat sticky and hairy variant occurs on the coast.

Bird's-foot Trefoil (Lotus corniculatus)
This familiar and well-loved peaflower is a major fodder crop in the USA and in some parts of Europe, but not in Britain. Fodder Bird's-foot Trefoil (var. sativus) can be recognised by their tall, upright habit, rather broader, pointed leaflets and smaller, yellow rather than orange-tinged flowers. This plant is apparently native to the foothills of the southern Alps in Switzerland and northern Italy. It were first observed by botanists along new or recently improved roads as early as 1966 in Tuscany, in 1969 in Denmark, Germany and Holland, in 1970 in Britain, in 1972 in Austria and in 1976 in France. Where hybrids have been recorded between alien and native plants, there is evidence that the upright habit of the fodder plant is a dominant character, which will lead to loss of variation amongst native plants.

Fodder Bird's-foot Trefoil has been widely used in seed-mixtures for roadside verges in Britain since the mid-1970s and has recently been reported from Ireland. Its use in wildflower seed-mixtures is partly a result of the limited availability of native seed and also an EC regulation that only approved sources of seed of agricultural species may be used commercially.

Kidney-vetch (Anthyllus vulneraria)
Like Bird's-foot Trefoil, this popular wild flower, one of the commonest peaflowers sown on road-verges, has limited availability as native seed. During the 1950s and 1960s, plants from central and eastern Europe, known to botanists as subspecies polyphylla, were widely reported on roadsides in Britain. Since the early 1970s the common plant used on new road-verges is a variant of subspecies caipatica, native to alpine valleys in central Europe. Both of these are more robust and erect than the native subspecies vulneraria and both have been grown widely in Europe as fodder crops. We have observed plants of subsp. caipatica being sold in pots as a native wildflower on market stalls, also at a Naturalists' Trust fair and at a 'green' nursery!

An unsuitable coastal variant of Kidney Vetch, with much-branched stems, is sometimes sold by nurseries. In many parts of lowland Britain, native Kidney Vetch is now rare, and it would be a pity for it to be replaced by non-native plants. In Scotland and Ireland there exists yet another subspecies of this variable plant, and on coasts of western Britain there is a rare and unique subspecies that grows on cliffs and sand-dunes.

Sainfoin (Onobrychis viciifolia)
The plant that is widely sown on roadsides is robust and more or less erect. A prostrate plant with darker red flowers grows in chalk grassland in Wiltshire, Cambridgeshire and elsewhere, which is very close to, if not identical with, var. montana, a plant of semi-natural grasslands on the continent. It is likely that this is the native plant reported by John Gerard in his famous Herball of 1597 from Cambridgeshire and Bedfordshire half a century before writer and antiquary John Aubrey first recorded the introduction of Sainfoin from the continent as a fodder crop. Some of the plants sown recently are so-called Giant Sainfoin, an even more robust variant of the common plant. This is a good example of the potential for ecological or genetic erosion of native populations of a plant that is not only an attractive wildflower but a fodder plant of economic value.

Salad Burnet (Sanguisorba minor)
This variable species has several subspecies in Europe. Fodder Burnet (subsp. muricata), originally from southern Europe and a plant quite distinct from the native Salad Burnet (subsp. Minor), is a common component of wild flower seed-mixtures. Long grown as a fodder crop and the 'Salad Burnet' of the herb garden, it can be recognised by the taller, more robust habit and larger, more warty fruits. As well as being employed widely in projects such as landscaping of roads and revegetation of mine-spoil, Fodder Burnet almost always substitutes for Salad Burnet in wild flower seed-mixtures and nursery stock.

Oxeye Daisy (Leucanthemun vulgare)
This species has been divided by botanists into several subspecies, even distinct species, in Europe. Much of the material included in wild flower seed-mixtures is the garden hybrid, L. x superbum. It is more robust, branched and has broader leaves than the more delicate native plant of meadows (L. vulgare). Widely sown and almost an indicator of the use of wild flower seed, this plant is common on recently landscaped road embankments.

Yarrow (Achillea millefolium)
Robust, branched variants of this common plant, often with pink flowers and probably of horticultural origin, are found in seed-mixtures. This species has several distinct variants in Britain, associated with different habitats.

Corn Marigold (Chrysanthemum segetum)
This popular garden plant and component of wild flower seed-mixtures is characteristic of acid soils and only very rarely occurs as a native on chalk or more alkaline soils. Its use in wild flower seed-mixtures has expanded its range in the countryside, obscuring the native distribution. In the past it was a major weed of cultivation on sandy soils.

Grasses
We have not investigated grasses in detail, but non-native material is used widely. There is probably no way out of this problem, as enormous quantities of non-native grasses, such as material of Chewings Fescue (Festuca rubra subsp. commutata) from New Zealand and North America, are important plants in agriculture and landscaping. They are often classified as agricultural crops and thus subject to EC regulations on seed purity and origin. Native populations of grasses undoubtedly survive on cliffs, sand-dunes and elsewhere and these must be conserved.

One non-native variant of a grass, in particular, has attracted the attention of several botanists. We have seen and come across several records of a robust variant of Yellow Oat-grass (Trisetum flavescens), 80-100 cm tall, that is distinct from the native plant and probably comes from S.E. Europe. This may well become a problem in restored chalk grassland, where the native plant would be appropriate.

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Acknowledgements
Plantlife would like to thank those who provided information and discussed the problems of introduced wildflower seed, especially Bronwyn Akeroyd, Dr David Briggs, Dr David Coombe, Dr Quentin Cronk, Gwynn Ellis, Paul Evans, Lynne Farrell, Prof. Vernon Heywood, Linda Laxman, Dr Alison McDonald, Dr Donald McIntyre, Vicki Morgan, Philip Oswald, Chris Preston, Peter Sell, Jonathan Spencer, Olga Stewart, Hugh Synge, Dr Max Walters and Dr Peter Wyse Jackson. Special thanks to Olga Stewart and Graham Easy for the illustrations.

We are grateful to Bob Flood (NIAB, Official Seed Testing Station) for data on seeds coming into Britain. We are pleased to record the assistance of Botanic Gardens Conservation International (BGCI), Kew, who provided the author with office facilities for a period during the compilation of this booklet. Plantlife is indebted to English Nature for their generous funding of this project.

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Further Reading
Baines, C. (1985) How to make a wildlife garden. Elm Tree Books, London.
Briggs, D. & Walters, S.M. (1984) Plant variation and evolution. Cambridge University Press. (A very readable account of the nature of genetic variation in plants, with many examples drawn from the British flora.)
Chambers, 3. (1987) John Chambers' wildflower garden. Elm Tree Books, London.
Department of Transport (1993) The wildflower handbook. D.O.T. Publications,London.
Gibbons, B. & L. (1988) Creating a wildlife garden. Hamlyn, London.
Rackham, O. (1986) The history of the countryside. Dent, London.
Stace, C.A. (1991) New Flora of the British Isles. Cambridge University Press.
Stevens, 3. (1987) The National Trust Book of wild flower gardening. Dorling Kindersley, London.
Wells, T., Bell, S. & Frost, A. (1981) Creating attractive grasslands using native plant species. Nature Conservancy Council, Shrewsbury.


 

 


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