I recently reread Michael Pollan's 1994 essay "Against Nativism." In it he argues against a loud minority (a minority I float in and out of freely depending on the topic) who, according to him, believes the following:
A vocal army of designers and taste makers has decreed that the “new American garden” is henceforth a place that:
1. Outlaws any human artifice in its design;
2. Grants citizenship exclusively to native plants (any immigrant to
be treated as “flora non grata,” with “invasive aliens” subject to
3. Resembles as closely as possible the “presettlement” American landscape of its particular region; and
4. Guarantees the right of self-determination to all its flora and (nonhuman) fauna, and bans the “brutal” practice of pruning.
This list could not be more out of date. Maybe two decades ago, when the native plant movement was certainly in its infancy -- and as wildly disparate viewpoints from all over the place were being expressed as it tried to find its footing -- it seemed more "radical." There are plenty of folks who find my belief in the wildlife value and design potential of straight species native plants radical and limiting, and particularly my philosophical and ethical reasons for doing so in a time of climate change and extinctions, but the design of native plant landscapes is not as rigid -- and should not be -- as Pollan assumes. Let's go through each point:
1. You can't avoid human artifice in design. The very act of creating a garden is artifice. Once you arrange plants according to your aesthetic and / or site requirements (the latter is often quite different than a wild, natural site), artifice is the name of the game. Naturalistic garden designers (or New Perennial or New American) try to blend human needs with environmental and wildlife needs, echoing and evoking that natural landscape which the plants came from. But even I don't believe we can have prairie in the city in the way it exists on the Plains; I do think we could replace lawns and seed in prairie for some cool habitat and effect, but that prairie would exist, work, and be managed much differently than one outside the city limits.
2. Yes, I design with as close to 100% native plants as I can, and I believe we should all strive for this goal. Wildlife has co-evolved with those plants, the plants call us out into the wilds of our home places and connect / awaken us to the place we supposedly love and respect, and we do not know better than nature. I believe a hosta or daylily or lilac and even butterfly bush are dead zones for wildlife, especially pollinators, and deny life instead of providing it. But I'm not going to personally condemn someone for having these plants if the majority of the remaining landscape is in native plants -- even if I'd love to see the remaining landscape fully used by natives for maximum benefit. We have to have an ideal goal in mind, a reach that outstretches our grasp by miles, to get to an even better place; if the goal or reach is only halfway, then the reality will be even less then it could be.
3. Once again, a designed garden is an evocation and an interpretation. It may use the same plants as presettlement / annihilation / eradication -- it may even copy the plant communities in ecological design -- but it can almost never be the exact landscape that was lost. The reasons for that are complex, starting with the loss of soil life, urban pollution and heat island effects, all the way to having to create landscapes that function for people as well as wildlife in an almost infinite array of configurations, from parks to hellstrips, to suburban yards to road edges to businesses, and to storm water mitigation and treatment.
4. In a human landscape you have to prune woody plants -- from reasons involving safety to design. I do advocate letting perennials self sow, letting plants move around a bit to find their way and teach us about what they want and how they act. A garden is not a static sculpture, it is alive and evolving, rich with the chaos of fractal geometry which helps it evolve, grow, and exercise itself in a web of life. We are free to pluck seedlings if we wish, or move them about -- it is a garden, after all, not a "wild" prairie or forest.
There are many other points I could argue, especially Pollan's idea that plants move around naturally, so who cares if exotics mix with natives (yet never before have they moved so quickly and thoroughly as during the last century or two, and never before with such blindness and narrow-minded purpose / hubris as to the effects that such movement causes). Pollan wants multihorticlturalism, but shockingly in that view Pollan is part and parcel of the system that has severely diminished biodiversity, leapt without thinking or knowing, and works primarily to seek immediate human good first and everything else second -- even if everything else contributes to our long term good. For someone so aware of the agricultural issues of our culture, it's a surprise and a travesty.