|Shirley Temple Peony|
Because my general attitude is not to harm living plants if they fit in with the garden ecosystem, I don't entirely sympathize with those who, after their natives-only epiphany, go and rip out all the offending exotics and completely redo the whole garden--it's a little too baby and bathwater for me. Better to evaluate on a case by case basis, and to make substitutions as opportunity occurs. For example, a climbing rose I loved died of rose rosette disease. Naturally I wasn't going to put in another hybrid rose, especially in that spot--but now I'm looking for a place to put a prairie, or Illinois, rose. In late summer or early fall you'll see me smother mulching a little more grass to make room for more native shrubs, forbs and grasses (described here).
Yes, I do draw the line at invasive species, many of which are dangerous to native ecosystems and plant communities--to have bishop's goutweed is to battle it, to see garlic mustard is to pull it out, and buckthorn exists to be chopped. In my garden, gone are some euonymous bushes, and I'm still working (forever) on the goutweed, old-fashioned orange daylilies, lily of the valley and English ivy. Unfortunately, many growers still produce and nurseries still sell all kinds of plants they just plain shouldn't. And don't forget, some natives can also wreak havoc in the garden: no old field goldenrod for me, thank you very much.
Yet there are plenty of non-natives that I'm not such a purist as to take out just 'cuz, though I wouldn't buy them now.
Came with the House
Hostas: along the the north side of the house, between house and walkway. Your grandmother's hostas-- by my estimation, these sturdy creatures are maybe fifty years old. Not so big, plain green leaves, not too showy lilac blooms with a nice scent in summer. Not a tetraploid set of chromosomes among them. Thrive on what I do for them, which is nothing.
Yews: in front of the house--horrors, someone call the landscaping police! Put in some time in the early twentieth century, I think. Many neighbors have taken theirs out, but hey, call me old-fashioned; they stay green, soften the ungainliness of my high front porch--and birds love to sit inside of them in winter. I chop at them from time to time with hand pruners, renewal pruning-style, to keep them in bounds. Sometimes I even them off a tad with hand trimmers (also discussed here).
Spring bulbs: big old-fashioned bright yellow daffodils, little white snowdrops and heavenly blue scilla.
In the Woodland Area
Back when I thought in terms of shade, part shade and sun instead of woodland, savanna and prairie, I put in a Japanese painted fern, some brunnera 'Jack Frost,' no-name astilbe and bleeding hearts. They do just fine among the Virginia waterleaf, virgin's bower, Jacob's ladder, Jack-in-the pulpit, woodland phlox and lady fern that went in when I learned better.
In the Savanna
The Hicks yew softens an objectionable corner--and the other day I watched some birds retreat into it when a hawk loitered about. And the white peonies, those gorgeous girls growing right next to the clematis 'Gurnsey cream'? They'll live to be a hundred, and I won't cut their lives short. There they flourish, among the purple coneflower, native columbine, obedient plant, New England aster, elm-leafed goldenrod and willow amsonia.
In the Prairie Patch
Which is what I call the sunny, unruly area where insect pollinators hold sway in high summer, where oriental lilies, raspberries, rhubarb, nepeta, oregano, mint and buddleia hold their own against cup plant, vernonia, Joe Pye weed, bee-balm and grasses. Honeybees cluster at the nepeta, bumblebees gravitate to the chives and beebalm and solitary wasps act as though the sweet autumn clematis is just for them. (The buddleia and clematis are potentially invasive in some places, but in my yard they die to the ground, and after being cut down are usually grumpy about re-emerging.)
Just naming these plants in the winter fastness of January brings warm sunny days to mind.
Note: One of the best lists of invasive garden plants and good alternatives is at the Chicago Botanic Garden website here. Also check out the Midwest Invasive Plant Network.
Update, 1/13/11: Just found the the compendious Invasive Plant Atlas of the United States. It's worth having a look. I've also put the link on the sidebar for future reference.
A Question of Trees
Gardening in Thatcher Woods With Help
Free Plants, Conservation and Reconciliation Ecology
Behold the Inglorious Garlic Mustard
May Has Almost Slipped Away