Plants out of place.
What I didn't expect was that the conference would be among the most interesting I've attended. Because it was about relationships between animals and plants, insects and plants, birds and plants, and fire and plants, dismaying news of the degradation of natural systems by exotic plants was balanced by a sense of revelation.
We heard stories about volunteers pulling broom and removing Cape ivy from the Santa Cruz mountains. There were stories about new uses of fire in the control of broom and yellow star thistle. There were stories about careful, thirty-year-long studies of sagebrush land, of the desert tortoise, of the Spartina invasions in our wetlands. There were stories about pampas grass, tamarisk, Cape ivy, arundo grass, pepperweed, iceplant, and cheat-grass, all involving relationships in the process of disruption.
Many of these plants are still sold by California nurseries and planted by California gardeners, whose back yards serve as springboards for the spread of Cape ivy, capeweed, vinca, broom, iceplant, English ivy, passionflower vine, pampas grass, and acacia. Not a few gardens in my town consist solely of such species, often donated by other gardeners, who, understandably, "have more than they need."
With strip-mining or clear-cut logging, negative consequences are evident from the first. The disruption of natural processes that comes with the invasion of native plants may not be obvious for a while. Once it's too late, we can evaluate the loss of good grazing that follows the invasion of cheatgrass and yellow star thistle, or the compromising of dune ecology that follows the establishment of European beach grass, Ammophila arenaria.
Slow, steady erosion of natural values resulting from the choices made by gardeners is evident in many situations, from public lands to private holdings. Old house sites in national parks demonstrate the consequences of early horticultural choices. A hike into the southern end of Point Reyes National Seashore begins with a stroll through eucalyptus, Cape ivy, vinca, Klamath weed, and broom, and every year it takes longer to get beyond the plant community I call "old ranchhouse."
Creatures that require a certain kind of vegetative architecture for forage and shelter find their lives disrupted by changes. Take the example of the California desert's wide-bodied lizard, unable to negotiate dense stands of the invasive Bromus rubens and consequently starving to death. Eucalyptus groves provide habitat for predators like the great horned owl, which preys on other owls. Diminished populations of the smaller saw-whet owl and others might be partly due to the unnatural advantage given to great horned owls by the increase in eucalyptus groves in the area.
Nutritional inferiority can be a subtle factor in the slow diminution of resources. In a study by Harold W. Avery, captive tortoises were provided either native or nonnative food. Those fed the native Camissonia boothii had a greater rate of protein assimilation and remained in positive nitrogen balance throughout the study, whereas those fed Schismus barbatus, a non-native, experienced a significant loss in total body mass. Creatures may be seen eating nonnative plants, but their ability to thrive on such fare cannot be inferred.
Restoration begins at home
In informal observations of my employees, clients, and neighbors, I've noticed certain developmental steps once the interest in native plants quickens, potential pathways for the back-yard restoration gardener.
First, the gardener becomes aware of some part of the native flora, often spring wildflowers, that is visually appealing.
Planting annual wildflowers will in most cases lead to immediate success and pleasure. A tentative reach into other areas, such as shrubs and perennials, commences. More difficult subjects, such as challenging native grasses, and native trees, which require long-term involvement and delayed gratification, are subsequently tackled.
Somewhere in all this activity, the gardener notices that most of the work involved is weeding. The story of gardening is the story of weeds. Possibly unique to California is the extent to which these weeds are offered in nurseries, bought, and taken home by gardeners.
An ounce of prevention is worth a pound of cure, and a stitch in time saves nine. Both sayings were made for exotics control. A lone pampas grass that could have been removed in an hour with a pick and shovel when it first appeared will now require a backhoe or a half-day's work. As Helen Hunt Jackson said of wild mustard, "one plant this year, a million the next."
A new broom sweeps no good
A stand of French broom grows along the road to my house, between the road and the soccer field. Genista monspessulanis spreads rapidly, and its seed is said to live twenty-five to eighty years in the soil; it is adaptable to almost all habitats in the coast ranges, but its root system is usually shallow, and in wet or damp soil, seedlings can easily be pulled up. Every year it bloomed, sometimes twice, set seed, and ejected its seeds five to ten feet from each plant, spreading itself down the road.
One year some of us decided we didn't want to watch this increasing degradation of the land. We publicized a broom-removal day, borrowed weed wrenches and root jacks, put up signs, and met with lunches, children, and a willing spirit.
Along with publicity and support, we also received our share of letters criticizing our efforts. I read the letters at the chiropractor's office, where the strenuous activity had sent me. Although I ended up lying down, I didn't take those letters that way.
Some colleagues recommended ignoring these critics. I thought their feelings and attitudes needed to be considered, and I find that controversy, though not pleasant, forces me to continue investigations of these issues, to my own ultimate benefit. My search for the reasons to control biological invasions has taught me as much as any other part of my work.
I often hear the statement, "I'm not native here either." The hint of longing to belong somewhere rings a bell with me. Being not native here, does it not behoove us to begin to know this land where we find ourselves, to honor it with a clear look rather than collude in its diminution?
We broom-pullers were mightily abused. We were called genocidal, racist, and, worst of all, "well-meaning." One of our critics extolled the beauty of wild lilac (Ceanothus) blooming along the roadside, companioned by yellow broom. Ceanothus, in my experience, does not reseed into stands of broom, and since most ceanothus is relatively short-lived, in twenty to thirty years there will be no blue contrast to the ubiquitous yellow of broom blossoms.
Another argument goes something like this: Who are we to interfere with the dispersal of plant species, ongoing for eons? Who are we to make presumptuous choices, favoring what we call native plants over the newcomers, which we ourselves also are. If broom plants outcompete natives, they say, it is interfering with evolution, the survival of the fittest, to remove broom.
This laissez-faire argument is called by one naturalist "letting your dog pee on a person after you've knocked him down." Does it make sense to maintain a hands-off posture in our wildlands, even as we see the plants we have introduced, and continue to introduce, move over the landscape like a conquering army, destroying food and shelter for those voiceless species we may not yet have heard from?
It may be that in a thousand years, broom and pampas grass will have found natural enemies, will have become part of the game instead of dominating it. By then, so many players will have been eliminated that it will be a much less interesting game.
In communities that border on open-space land or national or state park land, it is critical to educate gardeners. One lone gardener planting a hedge on the flanks of Mount Tamalpais created the vast stands of French broom now being expensively tackled by controlling agencies. The gypsy moth was introduced to the US to begin a silk-worm industry. European beach grass, now dominating a thousand-mile coast, was introduced to stabilize dunes. French and Scotch broom were introduced to stabilize old quarries. Kudzu was brought in to revegetate the South. Eucalyptus was brought in for firewood and lumber. Bermuda grass, kikuyu grass, and other weedy grasses were brought in as "miracle" lawns. Capeweed, iceplant, and Cape, Algerian, and English ivy were brought in as speedy ground covers. These disastrous introductions should influence future decisions about "the right plant for the job."
In many cases, native plants were rejected for these jobs. People want fast-growing hedges and screens, instant lawns, quick vines, and instant landscapes, and, in too many cases, the species that fall into those categories become invasive.
Gardening is supposed to be for pleasure, one of the few areas where choices can be made based on whim and personal preference, with no immediately apparent price to pay for casually made decisions. Gardeners may understandably resist limitations, given how few arenas are left to us where we can play without consequence.
We don't always know which species have the potential to become invasive. Showing restraint - resisting the plumelike flowers of pampas grass until we know for sure whether the supposedly non-invasive species really is so, forgoing the purple stalks of loosestrife until we are sure it will not invade in California the way it has in New England - doesn't seem much to ask.
Judith Larner Lowry is proprietor of Larner Seeds, which specializes in seeds of native plants of California. This article is excerpted from Gardening with a Wild Heart, available from Lamer Seeds, PO Box 407, Bolinas, CA 94924 and in better bookstores.
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||plant ecology|
|Author:||Lowry, Judith Larner|
|Publication:||Earth Island Journal|
|Date:||Jun 22, 1999|
|Previous Article:||Cats indoors!|
|Next Article:||Invasion of the maple snatchers.|