Native versus exotic—a key debate

Key to an understanding of the range of planting styles that can be described as ecological is the variety of attitudes to the use of native plants. The intensity of the debate between those who restrict themselves to native-only plantings and those who use non­natives (‘exotics’) varies considerably from country to country, with considerable implications for the resulting landscapes. Not surprisingly, there is a strong link between a habitat restoration style and the exclusive use of natives. This is seen most clearly in the US, where sections of the garden and landscape industry are now heavily engaged in the promotion of ‘native’ or ‘wildflower’ planting. However, little of the literature or other media forms, such as websites, addresses questions of design, either from a functional or aesthetic perspective.

What is so marked about the situation in the US is the tone taken by some of the proponents of native plants, which strongly asserts the morality of using them and their strict definition of ‘ecological planting’ as meaning ‘natives-only’. Consequently, the use of non-natives is seen as somehow unethical, and certainly ‘unecological’ (Druse 2001). A consequence of this is the reaction of those more pragmatic gardeners who wish to explore a naturalistic style using exotic elements. On several occasions the author has heard the expression ‘native Nazis’ being used by the latter to describe the former.

Typical of a pragmatic approach to ecological planting design is that of C. ‘Cole’ Burrell, who argues that ‘there is no point in using a native if it can’t perpetuate itself’. He is adamant that ‘our ecosystems are so trashed, that if I can rebuild any ecological structure then we must be doing some good’. ‘Non-natives’, he says, ‘can do much to expand the season for wildlife… But I do try to limit using non-native berrying plants as these can be carried a long way by birds, and some of our worst invasive species have been berry bearing shrubs’ (Burrell 2001). Part of the issue is what precisely constitutes a native. It seems to be a fact of life that our conception of geography is currently dictated by the nation-state and its boundaries, which are nearly always utterly arbitrary as far as nature is concerned. The increasing popularity of ‘native’ plants in the US has meant that, in the words of Rick Darke, ‘a lot of native plants are used way beyond their region.. .for example Echinaceapurpurea…a prairie plant…is being sold in Delaware as a native, but Delaware has never had any prairie’ (Darke 2001). The marketing ploy of selling ‘meadows in a can’ in the US has also meant the widespread commerial distribution of ‘mixes for broad geographical regions (that) may not be adapted for a particular situation’ (Bartels 1992:74).

Darrel Morrison defines a native as ‘a plant present in a region prior to white settlement’, although he recognises that ‘native Americans distributed plants too’ (Morrison 2001). However, Neil Diboll, a leading prairie restoration specialist and proprietor of Wisconsin-based Prairie Nursery, states that ‘I am not a purist, human beings are part of the ecology. and have always been implementors of plant distribution’, and is happy to implement the occasional prairie scheme in the Eastern states. ‘The only issue’, he says, ‘is if there could be an ecological problem from an invasive species or the polluting of a local gene pool of an isolated population’ (Diboll 2001).

Given its island status, definitions of native are easy to make in the UK, or might initially seem so. The island’s long history of human impact on the landscape has arguably made the opposing of ‘natural’ versus ‘cultural’ quite pointless, and in what is arguably one of the more successful of multicultural societies, the political overtones of a natives-only policy may sometimes seem offensive. Kendle and Rose’s discussion of the arguments from a variety of standpoints are as good a summary on the current status of the debate as can be found, and their conclusions reflect a classically British pragmatism (Kendle and Rose 2000:19-31). In Germany this debate does not appear particularly strongly. One reason for this is simply that two categories of ecological planting are clearly recognised, with each having clearly demarcated roles. Habitat restoration involving only native plants is used for both rural locations and many urban locations as a matter of course, and sometimes by legal requirement (Kendle and Forbes 1997). But in high-visibility public parks and other clearly designed public locations, another genre may be used to create a high-visual impact, the Hansen Lebensbereich style, with its intimate blending of native and non-native.

There is additionally considerable interest in natives among private gardeners, if we are to judge by the number of books on the subject, for example Witt (Reinhard 1994), but relatively little published material on the Lebensbereich style. Additionally, one must suppose that proponents of native-only planting (pace Ken Druse, see above) might want to keep their voices low, given the Nazi regime’s enthusiasm for native-only plantings. Gert Craning, in a paper on the ideological aspects of German nature gardening, notes that ‘in the late 1980s and early 1990s, books on nature gardens appeared in which more radical positions…were mildly rejected’ (Craning 1997), although he does quote from the Swiss U. Schwartz, who declared in a horticultural journal that ‘a weed is what is foreign. I count all cultivars as weeds’ (Craning 1997). In practical terms, there does seem to be a clear split between habitat restoration and the more ‘horticultural’ Lebensbereich school of ecological planting design which is much less extensive (discussed below). The latter always involves nursery-grown plants, whereas the former is nearly always reliant on seed, supplied by specialist wildflower seed companies. Landscape architect Uschi Grafen reported that ‘a problem here is that when you buy native plants from a nursery they may not be the wild forms, but horticultural forms. It is very difficult to get (true) wild forms as plants’ (Grafen 2001). In Sweden, like Britain, invasive non-native species have had a relatively limited ecological impact and there has apparently been little debate in this area (Hammer 2000).

Steve Martino, practising in the US southwest desert, is quite adamant that in many cases he is producing ‘contrived native plantings. people have to be around them’ so that not only does he use the occasional non-native, especially South African aloe species, but that cultivars have an important part to play in many of the locations he designs for, especially those of high visibility. Colleagues in the nursery trade actively search for new forms in the wild ‘which would make better cultivars for cultivation’, listing the usual aesthetic and horticultural criterias as well as those with thornless varieties as an important factor among naturally defensive arid-zone plants (Martino 2001).

Morrison, however, is sceptical about using cultivars; ‘in urban areas, there is a validity to using cultural heritage rather than just native plants, and for using cultivars. But there is a risk in overembellishing. I hardly ever specify a cultivar in a design’ (Morrison 2001). Cultivars of wild origin, as opposed to hybrids, or doubles, are more acceptable, although he is concerned that their use may restrict the gene pool and, therefore, the ability of a plant community containing them to reproduce and adapt effectively over time.