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Diversity in amenity planting

Volume 5 Number 2 - July 2008

Introduction

Botanic gardens form part of the continuum of open spaces available to the public in urban areas. As well as their more specialised roles in research and biodiversity conservation they provide recreational areas for exercise and relaxation. The planting and pathways are important as in any urban green area. But how important is diversity in planting when the plants are seen as one part of the amenities available to the general public in our city spaces? And what is meant by amenity planting? In its broadest sense, amenity planting is a wide-ranging subject. It covers planting in parks and gardens, roadside flower beds, roundabouts and cemeteries, and extending to supermarket car parks, motorway verges and public visitor attractions. It is in fact any planting in a public space. Those responsible for amenity planting include local authorities, trustees of private gardens and museums and tenants organisations.

Amenity planting – the traditional view

Amenity planting in any context including within botanic gardens, encompasses trees; both as specimens and in woodlands; shrubs, perennial planting in herbaceous borders and seasonal bedding. All of these types of planting embellish mown grass which has itself always been the dominant vegetation type in the amenity setting. The preferred landscape choice of many involved in the amenity sector is mown grass, along with seasonal bedding (annual flower planting). This is monoplanting and has been described by sceptics as ‘green concrete’ and is the antithesis of diversity in amenity planting. The reason it is so widespread is the minimal maintenance required to keep it neat (predictable, repetitive and mechanised) and its more physical qualities such as robustness and long season of ‘interest’. In the UK at least, much is made by local authorities of the cheapness per hectare of gang mown grass: in economy of scale it is unparalleled. Annual plants used to complement mown grass are planted in their thousands in every country that has the resources to do so - from Egypt to Mexico. These provide ‘colour and drama’ now understood to be an essential requirement of the average tax payer who provides budgetary support for amenity planting. Thousands of bedding plants are planted every summer to decorate the streets and parks. The Royal Borough of Kensington and Chelsea in London, for example plants at least 300,000 bedding plants every year for 100 or so sites around the borough. The resource intensity of this is considerable as these plants need a ready supply of water and nutrients in order to complete their swift, intense lifecycle. Mobile watering vehicles regularly irrigate the flowers that are planted during a hectic month in late spring and again in late autumn.

The managers in the parks departments would also see that planting 300,000 exotic flower cultivars….from Dahlia ‘Roxy’ to Fuschia ‘Maybe Baby’, tightly together in rows and shapes and creating a riot of colour that lasts just three months, to be replaced in autumn with pansies and bulbs, as very diverse. They are right from an artistic point of view, but this kind of landscape management is a far from sustainable from an ecological perspective and is expensive. Local authorities would argue that this kind of planting bolsters ‘civic pride’ despite the fact that it is economically and environmentally costly. Does civic pride have to come at this cost?

The influence of the ‘gardenesque’

Historically the influence of the ‘gardenesque’ underpins all of our thinking about planting. During the second half of the nineteenth century global influences and the greater availability of many types of flowers made it possible for parks to aspire to have the features of the great botanic gardens and private estates of the day. Many public parks had indeed been private gardens themselves before being taken over for the enjoyment of the public. Herbaceous borders, ‘parkland’, annual displays of bedding plants, Japanese gardens, Alpine gardens, Rhododendron borders… the list of features that constitute gardenesque is considerable. In their time, parks were very successful at maintaining and introducing these elements for the enjoyment of the public. Today however most parks departments are no longer the repositories of horticultural skill they once were, and they no longer have the resources to implement and maintain the highly formulaic garden features they formerly aspired to. Stripped down and simplified ideas from the gardenesque seeped out into amenity planting, hence the expanses of monoplanting that adorn our streets and roundabouts; monoplanting of shrubs, annual flowers and bulbs. This type of gardenesque ‘lite’ still forms the majority of our amenity planting outside our parks and, to some extent, within them.

Introducing diversity into amenity planting

Let’s consider this matter of diversity in amenity planting. What is it and why is it better than the traditional alternative? Diversity means a large number of plant species creating a variety of habitats thereby allowing numbers of species to thrive in balanced, permanent ecosystems. And why is it good? From an ecological point of view a range of co-existing species is considered able to exploit more resources than can a single species on its own thereby producing a greater biomass and the environmental benefits that ensue. A range of species is also said to be better able to cope with change, as an ecosystem, then a single species.. There are two theories as to why this might be so: firstly, at a community level, the greater the number of species, the greater the number of responses to different environmental stresses, which smoothes out variation at the community level; the second theory being that a large number of species in a community means that there are enough species to functionally replace those that are adversely affected by external pressures. (Dunnett 2004). It is true that a range of species planted in an ornamental setting is certainly less vulnerable to pathogens and environmental extremes than one sole taxon. Pansies planted en masse all with mildew are not an uncommon site on London’s Streets, as are rose beds blighted by black spot.

From an aesthetic point of view, despite evidence suggesting that people like things to be tended, peoples’ perception of landscape is favourable if there is a degree of ‘complexity’ to a setting (as well as coherence). Managed complexity, or diversity, is therefore what people want to see. Wildness is acceptable if the edges are neat…mixed plantings are accepted if they look planned rather than random. This requires skill at the management level to make wild and managed meet seamlessly. Spontaneous vegetation (also known as weeds) in an urban setting, left to colonise abandoned land does not necessarily constitute diversity as too often it is one or two highly competitive (normally exotic) species that dominate.

Environmental concerns, which now underpin every area of public life, have started to have an influence on amenity planting. Parks departments and others in the landscape planting sector have been and continue to think about how to make planting both diverse as well as resource-efficient. They have approached this in various ways. Many of the more forward-thinking managers of public spaces have experimented with sowing flower mixes redolent of annual meadows. Organisations such as Landlife International based in the UK receive a lot of public funding to involve the community in sowing wildflower meadows in an urban setting. These mixes can, however, be very vulnerable to annual weeds and a short (but often spectacular) burst of poppies, cornflowers and ox eye daisies cedes to three months of weeds that self seed and so the cycle continues. It can take many years (and much commitment) to restore the balance in favour of a natural succession of annual flowers in grasses. The reason for this is two fold….the soil in the amenity setting is more often than not much richer in nutrients than many of our soils that occur naturally. A small group of exotic plants exploit these nutrients and self seed very successfully making it difficult for introduced annual flower seeds to get a toehold.

Another very successful way of introducing diversity is simply not to mow the grass; differential mowing is a common practice in most amenity grassland management. Over time new species self seed and the unmown grass becomes a habitat in its own right with other species slowly establishing in the grassland. On the planting side, local authorities such as the new Potters Hill Park by Tower Bridge in London, UK have employed forward thinking landscape architects who are specifying swathes of tall perennial plants and grasses such as those pioneered by the Dutch architect Piet Oudolf. These are wildlife-friendly and easy to maintain. Oudolf uses a limited palette of tall perennial plants and grasses planted in swathes…. his is the herbaceous border re-examined with grasses playing a major role.

Using perennial plants again the University of Sheffield has done much research over the last twenty years to develop the use of naturalistic herbaceous vegetation in an amenity setting. This presents a middle ground between meadow-like planting and herbaceous planting and as well as being a resource-efficient way of introducing diversity into amenity planting. Using a large number of species of perennial flowers, or forbs as they are known, ‘prairie’ type planting is established; a site is sprayed with a graminicide weed killer and seeds are sown into a thick mulch of sand or compost which acts as a weed suppressant. Germination and establishment is generally very successful. Mixes can be tailored to damp or dry soil, they require very little maintenance and the resulting growth is very attractive to birds and invertebrates.

Management is the key to increasing diversity in amenity planting. For local authorities that do not have the resources to achieve nature-friendly management, wildlife trusts sometimes step in and take over the management. Such is the case of Brandon Hill Park in Bristol. Half of this park has been given over to the Avon Wildlife Trust, who are restoring it to a mesotrophic grassland, introducing native trees and shrubs and allowing nature to take its course. Botanic gardens and other parks, often have ‘conservation areas’ that are encouraged to be wildlife friendly habitats. Management is kept to a minimum - just enough to keep species diversity fairly balanced. These areas are accepted by the park users as long as all of their other needs are catered for, such as sport, dog walking, flower displays, benches, cafes and toilets.

Conclusions

Encouraging diversity in amenity planting is often constrained by the reluctance of those in charge of amenity landscapes to experiment. This is an area in which botanic gardens, most of which are in cities, could play a major role. Botanic gardens have always taken the lead in encouraging the conservation of plant diversity, and there is a growing focus on local habitats and vegetation types in their displays. They have in the main however, been slower to adopt some of the management practices discussed above – differential mowing of grass, sowing ornamental seed mixes or even using perennial plants experimentally.

Botanic gardens are repositories of increasingly rare horticultural skills and accumulated knowledge. They also have a history of plant-based experimentation - whether it be trialling tropical crops for agriculture or growing plants for medical research. This experimental approach could be extended to include to the wider amenity environment, notably the area of ornamental planting. There is no reason why botanic gardens could not aim to move away from the immaculate seasonal bedding laid on for the visitor and experiment to make seasonal ornamental planting less resourceintensive, with a greater focus on seed sowing - educating visitors and the wider greenspace community thereafter. Taxonomic order beds are often maintained by re-sowing every year, with seed being collected and phonological information noted; there is no reason why these practices cannot be applied to some of the seasonal ornamental plantings, to create diverse and suitable seed mixes with a long season of colour.

References

  • Dunnett, N. & Hitchmough, J., 2004. The Dynamic Landscape, Spon Press, London, UK.

Mima Taylor
9b Pemberton Gardens
London, N19 5RR, UK
Email: mimataylor@btinternet.com; arp06jht@shef.ac.uk