What are We Really Planting in Our Gardens?
In New England, spring is almost here. The urge to stop and admire the first blooms on the redbud tree or the spring beauties in the woods, to plant something in the garden, above all, the longing to spend more time outdoors has now become a compulsion.
I truly believe that gardening connects people to nature. We work with plants and soil, nurturing something, enticing it to grow. Gardening gives us a chance to become children again, burrowing our hands in the dirt. We grow vegetables to eat and flowers to admire, and feel that we have made the world a better place. But have we?
Gardening and conservation do not necessarily go hand-in-hand. For example, fertilizers make things grow, but are also some of the biggest sources of non-point pollution for streams and rivers. Watering makes things grow, but irrigation systems drain aquifers in many parts of the US, not just in the western states. Large-scale landscape plantings often employ the same plants again and again (no matter where you live), setting the stage for major pest infestations, which we often try to control with pesticides that threaten our health.
Sustainable gardening (also called ecological landscaping) is about applying conservation values to horticulture. Conservation values per se are a human construct, a set of beliefs that guide decisions about how we vote, where we spend our charitable dollars, which cars we purchase, and, yes, how we garden. In my mind, the essence of "conservation values" is (1) preserving biodiversity, (2) "doing no harm," and (3) protecting natural areas from destructive forces (within our control, of course). Using native plants in the cultivated landscape is one way to preserve biodiversity. (Native plants are plants that grew in the US before the colonists arrived. Sometimes a native plant is defined more specifically, such as 'native to Massachusetts' or 'native to New England'.) Native plants not only provide excellent and familiar foods for wildlife, but appropriate shelter as well. I don't necessarily believe that native plants are better adapted to an area than non-natives. The right plant in the right place means a healthier plant with less additional effort, native or not native. I would never put a native wetland plant in a dry, rocky site -- it won't do any better than any other wetland plant in the wrong place. But native plants offer something much more. Learning about and cultivating native plants builds a vital psychological and emotional connection to wild places. We love what we know. Grow it in your garden, and then you recognize it in the woods and fields. Growing native plants is not a substitute for nature; it's a door to another world.
As a conservationist, I know most gardeners don't limit their choices to native plants. I certainly don't, and I work for a native plant organization! It's critical, however, that gardeners "do no harm." If nothing else, we must avoid planting invasive, non-native species. Invasive plants are aggressive, non-native species that are so vigorous and successful that they spread into uncultivated natural areas and become dominant or disruptive to those systems. They are habitat generalists that grow well under a variety of conditions, producing prolific amounts of fruit or seed, or spread by underground runners or climbing vines. The seeds of many invasive plants such as the burning bush or barberry are carried by birds, allowing them to spread far beyond the area of original introduction. Or, like the Norway maple, roots produce growth inhibitors, making it impossible for native species to compete. Once established in new areas, invasive species often take over and out-compete the native species. These plants will never be completely eliminated from our natural areas, but we can do something. As gardeners, we must stop buying these plants, remove them from our yards, and tell our local garden centers to stop selling them. Then, get involved with local efforts to control them in natural areas. (See below under "Related Link" for a link to information about which species are invasive in your area.) Growing native plants, however, is just one small piece of the conservation question. Many of us consider ourselves environmentalists. But how well does that translate to what we do in our yards or landscapes?
Plants need water, but how much water is enough? If it only rains an average of 11 inches a year in Tucson, Arizona, why do people insist on having lawns? Why can't we install water sensors so that programmed irrigation systems don't water the lawn in the rain? Even in the northeastern US, irrigation systems for landscaped homes and commercial sites are pulling enough water to drain aquifers to dangerous levels, or turn rivers into muddy seeps. Some towns have responded with regulations limiting outdoor water use, but with rapid development and increased demand for water, it is not enough. Every gardener who believes in conservation should look at how they use water in the landscape. A conservation garden uses plants adapted to the site conditions, so that they grow well with little supplemental water. Xeriscaping is not just for desert gardens.
Water conservation is more than plant choices. It's about soil health. Add organic matter to well-drained soils and they hold more moisture. My town's water district agency requires new housing developments to incorporate 10% organic matter into the top 12 inches of soil on a newly constructed house site before they will activate the water meter. No water, no occupancy permit. It's an excellent incentive when cutting corners on landscape quality is often the industry standard. Mulches are another great tool for both conserving water (prevents evaporation) and feeding the soil. At Garden in the Woods, the New England Wild Flower Society's botanic garden, we mulch with shredded leaves, recycling nutrients and organic matter almost as nature does.
The issue of lawn comes into every discussion about conservation and sustainable gardening. Why must every new suburban house be surrounded by the largest possible turfgrass carpet? As a landscape designer, I like a bit of lawn. The texture and elevation contrast compliments a perennial border, graceful shrubs, or muscular trees. But lawns are not putting greens unless you are a golf-course superintendent. Lawns should have species diversity, be mowed at a height of 3-4 inches to keep the grass plants healthy, and the cuttings recycled back into the lawn. Functionally, it's still a flat green place. No need to use "weed and feed" products that apply pesticides with every use. No need to fertilize at all, except for a little compost early in the season. And most of all, no need to have too much lawn. A diverse assortment of perennials, wildflowers, shrubs and trees does so much more. It absorbs more rainwater so there is less stormwater run-off. The biodiversity created in these areas supports an incredible array of pollinators, predators, and prey, providing habitat, food and shelter in a balance that controls pest problems with little human intervention. Even green industry professionals are now recommending that nurseries and large landscaped sites create "refugia" for these organisms to encourage more effective implementation of natural biological controls.
Spring is here in New England, even if the snow still lingers in the shady corners of the woods. I've been watching a pair of broad-winged hawks checking out nesting sites for the last two weeks (and fervently hoping they decide to settle in for the season). For those of us living in northern climates, spring brings a sense of affirmation that cannot be ignored -- earthy smells, the first chorus of spring peepers, and bright colors. We begin our gardening rituals, activities that weave fundamental bonds between wild nature and human nature. But it's only real if we garden in ways that conserve what we value, so that what we do and what we believe are truly connected.
Cheryl Lowe is the Horticulture and Botanic Garden Director with the New England Wild Flower Society based in Framingham, Mass.
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Source: An ENN Commentary
Photo by R. R. Smith. United States Department of Agriculture/Research Service.