COST EFFECTIVE LANDSCAPES WITH A CONSERVATION VALUE

Gerard Russell, Heritage Seeds

Introduction

The idea of the environmentally sound landscape is not a new one; the landscape industry as a whole has recognised the value and has indeed expressed intense interest in all aspects of native plantings, either of native trees or shrubs or of floristically rich grasslands in amenity areas.

However the wild flower rich grassland is often perceived as a difficult to manage and exclusive affair which is only really effective in the comer of a school playing field where it can receive regular attention.

In fact, quite apart from the ecological value of combining native wild flowers with suitable grass species, a properly designed and executed wild flower seed mixture is a robust, persistent and c a t effective landscape material. It has the potential to very significantly reduce the costs of the amenity grass control burden, which in the UK currently runs at about f300 million a year.

plants (sward being the collective term for a whole grassland plant community). Exposure to light and water is vital in the pre- germination of many species, which in some cases may take up to eighteen months before they become established. If sown at the conventional amenity grassland rate, cover would be quickly achieved and stifle any further development.

The cost of wild flower seed is attributable to the difficulty in growing, harvesting and processing seed from low yielding plants. In the majority of cases these operations are carried out manually and without the assistance of chemical weed control, (it is of course imposible to spray weeds that are growing within a crop of weeds).

This fact accepted, wild flower seed mixtures cost 12p per square metre which is significantly less than 15p per square metre for traditional grass mixes. This is quite apart from the massive financial benefits of reduced maintenance costs once the area becomes established.

for a given area by 80%.

There are of course restrictions with the use of wild flower mixes, as indeed there are for the use of any landscape material. However most of the problems are restricted to areas with easy public access, for instance maintaining rights of way and litter attraction can present difficulties, hence the siting of wild flower mixes in these areas needs to be judicious.

seed.

Initially the problem facing landscape architects or local authority managers in relation to wild flower mixes was one of availability. This problem has lessened in recent years with the emergence of specialist wild flower seed producers as well as many of the amenity seed houses who are now offering a wild flower mix in some form. However, the wild flower seed industry is relatively new and although its products are in great demand, very little technical infoxmation is forthcoming for the consumer on how to practically set abut effectively using wild flower seed mixes. Many forward looking establishments who use these mixes become disappointed, mainly for want of technical advice.

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Table 1: RelatIve cost per M' of both wild flower and amenlty mixes

Type of Mix Sowing Rate Cost per Kilo Costm* g/m' (C) @ence)

Amenity Grass Parkland Mix 6 Species 35.0 4.28 14.98

Wild Flower Sandy Mix 34 Species 4.0 31.8 12.72

Wild Flower Clay Mix 32 Species 4.0 29.9 11.96

leliab ility As a result there are many regularly cited and m~ular - - - - _ misconceptions regarding the use of wild flower seed mixes, namely its expense, reliability, rate of colonisation and the ease of maintenance.

Expense

It is true that the cost per kilo rate for most wild flower seed is on average f30-60 per kilo compared with f4.20 per kilo for a standard amenity grass seed, but it must be noted that it is only sown at a miserly 4.0 @sq metre against 30-35 g/sq metre for amenity g r a s seed. The low sowing rate is due to the need to maintain an open sward during the development of the perennial

In this area the greatest majority of the problems or failures derive from soil fertility, for instance if the site is too fertile for the wild flower mix to succeed. Native plants are unable to compete for light and nutrients with cultivated grasses and as a result are swamped. This can be overcome by reducing soil fertility and maintaining a relatively low nutrient level as part of the on-going maintenance, this acts to suppress the grass species in the sward and allows the other perennial plants to succeed.

Other failures can be attributed to either mixes sown that are incompatible with the soil type or the emergence of pernicious weeds after cultivation that again compete with the perennial

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plants in the mix and then becoming dominant; Docks (hrnex The design of the sward closely follows the constituency of obrurifolia) or Thistles (Circium sp.) for example. This problem traditional agricultural hay meadows which would be cut once a can be easily avoided with pre-cultivation treatment using a year in the late summer, generally late August, for a hay mop herbicide that is readily absorbed by plants but has no residual rather than constantly grazed during the growing season. Hence effects (such as glyphmate). this type of sward reduces the frequency of cuts necessary for

amenity areas from possibly fourteen cuts a season to one cut in The maintenance within the fvst year is critical to the success and the late summer. longevity of the sward. A lack of attention or badly timed maintenance within the fvSt eighteen months following sowing hrge scale Applica~ons will allow total cover of vegetation to become established before all viable seed is able to germinate, hence restricting the number of species represented in the mature sward. Roadside verges may be regarded as a problem in so much as they

are large areas of land with little amenity value that need to be

Colonisation covered quickly and permanently but on a budget much smaller pro rata than any area of parkland.

Many institutions, notably Oxford University, have conducted This diIemma generally results in the 115e of low cast, but research into the nature and rate of colonisation of native plant unfortunately Vigorous agriculturally derived grass mixes, often species in their natural habitats. All the results concur that native including large percentages of polyploid rye grass, this differs plant material will not spread by seed unless it is presented with from native rye grass in that the process of breeding has resulted bare ground. Consequently the length of time that the soil remains in doubling up chromwone numbers leading to a vigorous and exposed is critical and this period varies widely between species. oversized plant. The greatest perceived benefit of using such a This was graphically illustrated at the end of the First World War product is its fast germination which can be. as low as 3-4 days in with the emergence of the ubiquitous poppy that capitalised on the some cases. However the resultant effect is a vegetation control huge areas of decimated pasture land to great effect where headache. If left unchecked the site becomes over grown and previously constant competition had suppressed germination. In unattractive and necessitates cutting up to eight times in the practical terms this means there will be no spread of native seed growing season. in to other established plant populations or more importantly in to existing grass swards. Genetically modified grass species designed for agricultural use

have several drawbacks making them unreliable for use in amenity Consequently, any attempt to enhance the ecological status of an areas. The vigorous species are able to fully utilise soil nutrients, existing g m s sward by simply reducing the number of cuts per hence without the application of fertilisers, in the course of three season without reducing soil fertility or creating bare ground or four seasons the sward will exhaust available nutrients and opportunities leaves no potential for colonisation. Hence there is result in substantial thinning and death of the plants, thus allowing no gain in the numbers or distribution of species. Under an the incursion of aggressive weeds and woody species intensive management regime any supressed herbs are likely to be. characteristically Bramble (Ruburfiuiticosu) and Elder (Sarnbuclrs low growing, m t t e forming species such as daisy (Bellis nigru). This succession is commonplace on most large perrenis) or Selfheal (Prunnella vulgaris). If the regime alters maintained verges, although the species invading will vary plants are unable to compete with the sudden change in foliage depending on soil type and fertility. height and die out, this is undesirable as the numbers of species represented declines. As a result of the genetic modifications, which are designed to

increase green plant material yield, many other facets of the grass Therefore, the enhancement or enlargement of valuable grasland p h t s are altered, and as well as becoming nitrogen hungry they can only be achieved using seed, as although the are= are self also become short lived. Therefore it is unusual to fmd an perpetuating they are not invasive. However some aggresive agricultural strain of any species that is more than three seasons species of meadow land plants with relatively short life cycles are able to establish into damaged grasslaud utilisiing very limited bare ground opportunities especially Ragwort (Senico jucobaea). This colonisation occurs strictly as a result of poor management, and in agricultural situations as a result of overgrazing.

Maintenance

Mast of the operations for the establishment of wild flower mixes are similar to that of conventional grass areas, which means that establishment costs for both amenity grass and floristically rich grassland are practically the same. However the timing of the operations varies from traditional grass swards.

The fmt year maintenance for a wild flower area is designed to maintain an open textured sward rather than to achieve total cover. It is the subsequent maintenance of wild flower grassland that presents the greatest opportunity f a substantial savings in maintenance costs.

old.

Clonal species of any plant express identical reactions to their environment. where the lack of genetic diversity makes the population susce@ible to environmental influences such as drought or disease. In addition they are also sterile from intensive breeding, and thus there can be no ~ t u r a l regeneration inside the sward, hence the invasion of aggressive weeds which capitalize on the bare ground opportunities created by the diminishing grass.

Native Material

Native plant material from the wild has many advantages over cultivated grasses or indeed cultivated perennial dicots such as Yarrow (Achilles rnilkfolium sariw) or Red Clover (Trifiliurn protense suriva), both commonly used in wild flower mixes but baring little resemblence to the native strains. From a purely botanical point of view, a population of uncultivated species carries a far greater range of genetic information than does a

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population of bred species. Breeding has the effect of enhancing a few desirable characteristics, but in the process of exhaustive selection necevary to achieve this, many other linked facets of the individual are diminished.

The action of constantly rejecting all but a few members of a population that show desirable facets and hence reducing the variation gives a homogeneous population with a reduced ability to react to the environment.

Whele this situation is acceptable inside the realm of intensive agriculture where a ley may only be expected to last for two or three seasons, when applied to amenity landscapes, especially where management is minimal, degeneration and succession is inevitable.

Native material however has the advantage of a diverse range of characteristics which creates a robust product. However ensuring diversity can be equally as demanding on the grower as can a breeding programme. All wild flower seed used in this country should derive from British native plants, so that resultant plant material is able to flourish under the particular demands of the British climate. Seed used for production plants must derive from more than one parent source to increase the range of genetic information present in the resultant seed crops. Furthermore, plants for production should be no more than one generation removed from the wild as this reduces the risk of unwittingly breeding production plants. The proportion of seed mixes should wherever possible reflect proportions of populations in natural communities, again this will aid subsequent stability.

The trend of commercial production has tended to pander to market forces in that the design of the mixes revolves around the cost of the ingredients, the cost being dictated by the complexity of seed extraction. This results in seed mixes being designed down to a price rather than up to a standard

When purchasing a wild flower mix it is important to establish provenance of the constituent species as all too often seed houses will select easy to grow strains of native material or even substitute native perennials with agricultural herbs with disastrous effects for the recipient site. When put together the interaction is one sided as the relatively vigorous bred plants are able to germinate quickly and swamp emerging native species, the short lived cultivated plants then die out and leave opportunity for the invasion of aggressive weeds.

There have been several incidents involving major seed houses who in an attempt to cut comers have substituted expensive ingredients for cheap agricultural varieties, the most extreme example of this was the emergence of F1 hybrid carrots in a wild flower area. This sort of practice is dimhidm ' g but is clearly damaging user confidence.

The constituents appearing in commercially available seed mixes vary greatly in number, origin and proportion. The generally accepted proportion is 80% gas to 20% perennial wild flowerg any increase in the proportion of wild flowers gives considerable benefit to the resultant sward but increases initial costs prohibitively.

It is a widely accepted ecological principal that stability derives from a diverse range of species co-existing in any given habitat. Therefore the lower the number of species represented in a community the less stable it becomes. Traditionally managed hay

meadows, often consistently cut for several hundred years, all exhibit upwards of 40 species of flora. It therefore follows that for B contrived floristically rich grass land to thrive it firstly should contain at least 30 species and secondly must be consistently managed. If this is the case this type of sward is, as far as it is known, sustainable indef~tely.

The role of wild flower mixes in large scale landscape construction as a practical material to aid the development of a site is not widely acknowledged. Roadside verges form a particularly pertinent application for the establishment of floristically rich areas as they are not generally subject to public pressure of access in the same manner that urban amenity areas would be. This allows for a much leu intensive maintenance regime.

In areas where soil erosion and or steep banks are potential problems, wild flowers have distinct physiological advantages over 100% gas mixes. These are effective in retaining soil with either invasive fibrous rhizomes or tap roots that penetrate the subsoil far more effectively than fibrous grass rmts which tend only to be effective in the first 3Omm of topsoil. This is especially valuable where homogeneous clay subsoil is liable to slump.

Construction

New construction schemes, especially involving large scale excavation and recoatouring. give the potential for significant savings through the use of a wild flower mix. Generally the specification depth of replacement topsoil for many road verges or embankments is 15Omm. If there is sufficient topsoil stored on the site its replacement constitutes a large percentage of the landscape costs. These cost savings are even more evident if the works require the importation of soil which necessitates finding a substantial and consistent supply from outside the site. The avoidance of this operation has obvious Financial benefits.

Wild flower mixes have a far lower topsoil requirement, 4Omm is sufficient in the majority of cases because the fertility associated with topsoil is unnecessary and damaging to wild flower mixes as it favours luxuriant grass growth.

Where topsoil is abundant on the site and only 40-5Omm is replaced, the surplus stored soil can be used for other schemes and indeed is a readily marketable commodity in most areas. Sales of the surplus topsoil can offset much of the construction costs and may even contribute to a profitable scheme.

The creation of less fertile soil conditions then eliminates the need to apply any base dressing of fertiliser possibly saving a further fl2Qhectare for materials and a similar amount for labour and machinery. Fertiliser is nct required during construction or at any other point during the development of the sward.

Habitat Values

The financial argument for using native plant species should be self-evident. The ecological gain from this type of planring needs to be put into perspective in relation to existing habitats.

Gradand supports relatively few species of plant and animal life if compared with broadleaved woodland where an oak tree will support over 200 species of micro flora, vertebrate and invertebrate life. This is approaching the total number of species

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supported by a whole acid grassland habitat, although this merely other plant species and allow succession to acid woodland. illustrates the differences between the habitats and is no reflection on the stability of the ecosystem. Public Awareness The inclusion of native flowering plants within any area will increase invertebrate activity as the number of plant species relates directly to the amount of activity supported. To optimise this effect the planting should be co-ordinated both within itself and the local environment. This involves the production of a balanced blend of species suitable for the existing soil type so that each will establish in population numbers close to that of existing native communities. This will avoid violent swings in the population numbers for each species and shorten the length of time taken to reach a state of dynamic equilibrium within the ecmystem, hence reducing the need for management inputs.

The support of the public in any such venture is of great importance for the success of any scheme, especially in urban areas, and any reservations about the use of wild flowers generally arise from lack of awareness. For local authorities in the UK with the advent of the Compulsory Competitive Tendering system and Poll Tax constrictions, local authorities are more accountable and therefore under more pressure than ever to be seen to invest wisely. If at the same time the demand for an ecologically sound urban environment is to be satisfied this must have positive effects for the use of cost effective landscapes.

Quite apart from the ecological value% a well executed North Meadow, Cricklaid in Wiltshire, UK, now under the floristically rich grassland is an attractive and valuable man%ement Of the Nature colnswancy Council* is Land feature. However, purists do argue, and quite rightly so, that there where a traditional a@eement between landlord tenant are no substitutes for native habitat% and therefore peat effort restricts the use of land to consistent annual hay removal and should be expended in the protection and conthwd autumn grazing. It has a documented history for over 800 years of such areas. during which time the management has been constant. The area has a Population Of some 120 Plant s p i e s which is However, although grassland is essentially a contrived landscape high and hence valuable. However, it should be remembered that importantly the majority Of British grassland habitat% with the possible urban situations dictates that its ecological contribution should be exception of some downland, are largely resultant from ma-sej, the use of wild flower made this easily

are therefore contrived.

its prevalence in both agrarian and

agricultural activity since the Land E n C h ~ ~ e s Act of 1740 and a,-heivable even within the present economic comw&ts.

However with the use of genuine native seed it is now possible to replicate meadowland areas with up to 60 represented species. Contrived meadow sites have several ecological benefits when used near or around existing valuable sites as a buffer effect is achieved where the effects of adverse influences from outside the habitat are reduced because of the change in the proportion of area against the perimeter, for instance venerability to chemical spray driit or nitrification of water c o w s is increased. Hence the larger the area the more resilient it becomes to environmental change. Therefore if the site is stable the maintenance costs of the area will remain minimal.

Specific Habitat Creation

Within the realm of amenity landscape the opportunity also exists for the creation of more specific habitats notably for the encouragement of butterflies and other invertebrates, this is achieved with the inclusion of food and nectar plants. The siting of such a scheme would of course need to be well thought out in order to provide. adequate shelter.

Heathland creation has many special management and establishment problems but also has much potential to preserve the now diminishing dry heaths in the South of England where continued development has resulted in fragmentation of the remaining areas of native Dorset heathland The isolation of habitats, either through building or agricultural development, has many effects on the overall ecology of remaining areas. Smaller habitats have less oppofiunity for internal variation which then restricts some plant species. For instance in relation to vertebrate activity, predatory animals such as the Hobby (Falco subhteo) need 600 acres to support a single breedw pair. AIso adjoining agricultural activity can effect rabbit numbers, where it is critical to have a stable population in order to control the invasion of bracken (Preridium aquilinum) which if unchecked will swamp all

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