New native plant communities

Altering the species composition of a plant community to make it more visually appealing is one way to make native plants more exciting to a public whose appreciation of ecology often goes no further than getting a nice warm buzz from hearing the word. It is an approach that is most advanced in the US, although a long-standing and bold statement of the possibilities can be seen in the parks of Amstelveen, a suburb of Amsterdam, in the Netherlands. In Britain, the planting of rhododendrons and other exotic shrubs in native woodland is a nineteenth-century example of this style.

It is theoretically possible to ‘tweak’ a wide range of native herbaceous plant communities for artistic effect, which may include the following:

– leaving out less visually appealing elements

– shifting the balance from grasses to more decorative forbs

– leaving out taller elements

– concentrating on species that will be decorative for one particular season

– concentrating on forbs with particular coloured flowers, or elements with other

particular aesthetic qualities

– aiming at a ‘minimalist’ effect by reducing visual complexity, usually achieved by

reducing the number of species – creating combinations of species that, although native to the same region, might not

occur together in nature.

A good example that combined several of these approaches was a planting carried out for an area in front of the General Mills corporate headquarters in Minneapolis, Minnesota, in 1982. The landscape architect in overall charge of the project, Michael van Valkenburgh, described how ‘we got this idea of an embracing grove of trees with an abstraction of a short-grass prairie on the inside’ (Gillette 1994). The tree species used was Betula nigra, which is not normally found in conjunction with short grass prairie. Matthew Urbanski, a colleague of van Valkanburgh described how ‘it comes out of the garden tradition… It’s using some natural planted forms—the grove and the prairie in a compositional way’. Two native grasses—Schizachrium scoparium and Sporobolus heterolepis, and a sedge, Car ex pensylvanica—were used to create a knee-high ‘grassland’. The sedge flourishes in shade, an advantage as the trees grew. A limited number of forbs were also included: Asclepias tuberosa, Liatris aspera and Lupinus perennis. The artifice of the planting was further advanced by being dissected by very straight granite paths.

Leading specialists, Prairie Restorations, were charged with developing the prairie. Prairie Restorations’ Ron Bowen argues for as much diversity as possible, as ‘we believe it equates with stability, so the more diversity, the fewer problems’. However, he accepts that in ‘half’ the plantings that his company carry out ‘we are designing for aesthetic effect’, particularly with areas smaller than an acre, ‘which can’t really be called a prairie’, the proportion of forbs to grass is increased from the ‘natural’ 20:80 ratio to ‘typically 50:50 or even 80:20’ (Bowen 2001).

The number of species used for even really authentic habitat restoration schemes may still be substantially lower than what would be found in natural examples of the habitat, as Bowen points out when he states that ‘a plant community may have 200 species, of those only a third may be (commercially) available, and of these we may well end up planting only a third, as the others may be uninteresting, noxious or invasive’ (Bowen 2001). It therefore follows that further restricting the palette for aesthetic reasons may restrict the ability of an authentic plant community to develop.

How far one can tinker with native plant communities before damaging their integrity, and, hence, their stability is a question of major importance. Neil Diboll of Prairie Nursery is definite that there comes a point when reducing species diversity in a habitat can create problems. Citing the prairie, he states that certain species do not appear to do as well in the long-term when deprived of their normal companions, for example Baptisia lactea sets seed only very poorly in the absence of grasses. Problems may also occur as the prairie negotiates succession; short-lived species may die out and not be replaced, or one species may dominate in the absence of competition (Diboll 2001).

Diboll does, however, have considerable latitude over the appearance of a prairie; 1 have the bias of an ecologists training. I am not a gardener, it’s too much like hard work. but we have gardening with seed mixes’ (Diboll 2001). The company’s seed mixes are generally skewed towards forbs, in addition to which they can custom mix seeds for particular effects, such as for colour, season or height. Forbs used for these effects often include species of Liatris, Echinacea, Coreopsis, Rudbeckia, Asclepias and Aster. Potentially invasive forbs, such as Rudbeckia hirta and some Solidago species, are minimised however. Diboll is confident that ‘our custom design mixes do not compromise the ecological integriety of the project’ (Diboll 2001).

Broadly speaking, there are two types of naturally occurring prairie, the more droughttolerant western short-grass prairie and the eastern tall-grass prairie. In cultivated situations, these two variations can be used for different landscape effects; short-grass prairie is particularly useful for surrounding buildings or for small spaces, tall-grass for larger areas or to act as a background (Diboll 1998). Areas can be planted so that there are different concentrations of decorative forbs, or where the forbs are kept constant and the grasses change, which creates particularly attractive autumn scenes when the grasses change colour and produce mature seed heads. So long as good species diversity is maintained, these aesthetically determined compositions can be very successful in the long term and they are not even particularly ‘unnatural’, as one of the fascinating aspects of wild prairie is just how much species-composition changes from area to area. These changes, says Diboll, ‘are best experienced through walking along trails, the pattern of which can be changed from year to year’ (Diboll 2001).

Stylised ‘natural’ plant communities can also be interpreted as fulfilling another set of criteria in addition to the ‘ecological’ or the ‘aesthetic’, cultural and historical. Meadows are not, of course, ‘natural’ but a semi-natural habitat that is the result of traditional agricultural management, as is much European woodland, most obviously in the case of coppice and much of the American prairie may have been human influenced too. Creating areas of such habitat can thus also be seen as developing a link between the present modern landscape and the history and culture of the area. Continuity, memory and local distinctiveness can therefore all be emphasised.