I was out weeding my native plants garden when a houseguest chided me about the ethnic cleansing that seemed to be happening there. Targets were dandelions, salsifies, thistles, chicories, henbit and donkeytail spurge, which try to crowd out naturalized grasses and bee-balm, penstemon and Jacob's ladder.


I have the satisfaction of knowing that what I toss out flourishes elsewhere, up and down my street in Boulder, Colo. As aggressive as they may be, most are themselves native plants and thus possess an ancient claim to their presence here.


I stay away from exotics. Santa Fe is plagued by Siberian elms and the Colorado Plateau by tamarisk; the Rocky Mountains are infested with cheatgrass, knapweed, leafy spurge and Russian olive. Meanwhile, this area offers donkeytail spurge (Euphorbia myrsinites) as our gift to Boulder Mountain Park and, by extension, the rest of the Rocky Mountains.


Donkeytail spurge is a mirror-like reflection of ourselves, especially if one is of European descent. It's an aggressive invader that is becoming naturalized in North America. Just like those ranching and logging families that have been in the West so long that they almost believe they originated here, spurge is making a home for itself. It won't be long before there's no one left who can remember what the prairies and foothill meadows looked like before the onset of spurge.


For years I've seen this stuff overflowing Boulder gardens, an attractive blue-toned succulent that thrives with little water. In early spring, its blossoms glow a pastel green under overcast skies. As it reaches for the sun, entire fields of it nod in unison, facing a single master.


I saw it first on the mesas west of town and wondered whether it was a "naturalized native." The wild rose, for instance, was introduced by European gardeners to North America, and is now a prominent and lovely wildflower of the American West. Toadflax, an aggressive exotic, came here by the same path. When toadflax is called butter-and-eggs, it is a sunny-meadow wildflower pictured in Audubon guides. Few, however, are ready to declare that ubiquitous Eurasian import, tamarisk, naturalized (HCN, 5/25/98).


Like tamarisk, donkeytail spurge is a fast-moving, aggressive invader. The City of Boulder Open Space program lists it as an "ornamental exotic" and recommends not planting it in the first place and pulling it when found growing wild.


It's poisonous and some people have been hospitalized from allergic reactions after contact with the milky latex from broken stems (See Longmont Daily Times-Call, 9/18/97, "Children bit by donkey tail'). Ignore spurge at your peril; it will soon be everywhere. My neighbor's "xeriscape" needs little water and boasts many healthy patches of it (-the deer won't eat it'). I see him out there pulling up great gobs of the stuff. He can pull all he likes; anything less than complete elimination is an exercise in frustration. Even then, somebody else's patch will try to colonize his garden - seeds spurt up to 12 feet every time a seed pod bursts.


Spurge never stops trying; that's the key to its success. We gardeners grow weary and tired, but not spurge. Is it any coincidence that it rhymes with "scourge'?


Many gardeners have extended the idea of xeriscaping to mean a waterless and maintenance-free garden. Anybody who has ever gardened knows what an oxymoron that is.


Xeriscaping's logic is that we live in a water-starved region and ought to garden that way. Such an approach can produce nice results when done right but often results in two disturbing trends. One is that as we conserve, the saved water gets appropriated for new development, habitat is subsequently destroyed and we remain just as water-starved.


The other is that we introduce from our rock-gardens a pantheon of the world's hardiest dry-climate species into the West, species whose colonization and naturalization seems irreversible. Think of the tumblin" tumbleweed that rolled all the way from the steppes of western Siberia into all those John Wayne movies.


Think twice before you plant that new exotic. An innocent garden flower could trigger an ecological nightmare.


No nightmare, however, awaits the native-plants gardener. The worst-case scenario is that a plant returns to its native range. Natives come ready-made with checks and balances in the native ecosystem. Oh, there may be the occasional bad dream. A hungry family of native herbivores may congregate in the garden and eat every exposed green thing, lock, stock and barrel. A cloud of aphids could descend upon prize columbines and quaking aspen. A hot spell and furnace-blower windstorm will desiccate even these drought-tolerant plants.


Put up the fences, folks, and buy some ladybugs! You might even want to get out the hose and indulge in some guilt-free watering. n





Evan Cantor is a gardener, writer and artist in Boulder, Colorado.