Excerpted from “Native Plants for New England Gardens’’ by Mark Richardson and Dan Jaffe.
Few things reflect the unique character of New England like its native plants. Native plants not only provide beauty and highlight the distinctiveness of a region, but they also help to support healthy ecosystems, providing habitat for local wildlife. Native plants evolved over millennia within a region’s environment, making them well adapted to a particular place, and so when properly sited in a garden, they require fewer inputs like irrigation, fertilizer, and pesticides to remain healthy. As our landscapes become more developed and the space between wild areas grows wider and wider, it is critical that we think of our managed landscapes, like the gardens we all care for, as more than just ornamentation. Our gardens are critical ecosystems, providing habitat for wildlife, capturing and filtering stormwater, and sequestering carbon. Native plants are fundamental components of these urban and suburban ecosystems, and by using more of them in our gardens, we can keep our environment healthy and celebrate the charm of the region we call home, New England.
For those of us who work with native plants professionally, defining what we mean by “native’’ can be a colossal challenge unto itself. Generally speaking, native is defined by “where’’ and “when.’’ In other words, native plants are considered to be those that existed in a given location at a specific point in time. The first point, location, is simple enough, but requires that you choose parameters. From broad terms like “North American native’’ to narrow terms like “native to Middlesex County, Mass.,’’ the gardener, landscape designer, or horticulturist sets the criteria and chooses plants that fit. At Garden in the Woods, the New England Wild Flower Society’s native plant botanic garden in Framingham, and for the purposes of selecting plants for this book, native plants are those that naturally occur in the US Environmental Protection Agency’s Ecoregions of New England.
The second point, when, is a little more complicated and can be a bit more controversial. For simplicity’s sake, we define native as dating back to European settlement. While using a rigid time parameter implies that natural plant migration halted when the pilgrims arrived, it also makes it easy to determine which plants migrated on their own and which were introduced from outside the region. Species migrate constantly; in fact, every plant in our flora migrated northward since the last ice age. When plants migrate into an area on their own, they do so slowly, typically by natural movement of seed by wind, animals, and water. Natural migration is obstructed by geographic barriers, like oceans and mountain ranges. While the vast majority of introduced plants are innocuous, there are myriad examples of introduced plants that have become invasive.
Invasive species are not simply garden thugs that take over a perennial border, like lily-of-the-valley (Convallaria majalis); rather, they cause substantial harm to natural lands, like oriental bittersweet (Celastrus orbiculatus). Working with native plants is one great way to ensure the plants in your garden will not contribute to the disastrous environmental and economic effects of invasive species, which are estimated to cost the United States more than $120 billion annually.
RIGHT PLANT FOR THE RIGHT PLACE
It’s easy to get lost in a garden center, admiring the various colors and textures and thinking about where that great new plant with its steel-blue flowers might look best in your garden. Gorgeous plants can be hard to resist. Choosing native plants is one easy step toward knowing whether they will struggle or thrive in your garden, but it’s not the only step. It’s reasonable to assume that a native plant will be hardy enough to survive our winters and that it is not invasive. Beyond that, gardeners must think about that ever important principle: the right plant for the right place.
All plants, regardless of their origin, have specific cultural requirements, and if planted in the wrong place will struggle to survive. The key is to visit the garden center armed with a good understanding of what your garden has to offer and to choose plants based not only on their looks, but also on their cultural needs. Cardinal flower (Lobelia cardinalis) is stunning, but plant one in a dry, shady site and it will never flower. On the other hand, plant bearberry (Arctostaphylos uva-ursi) in a wet spot, and it will rot. When selecting plants for gardens, the goal should be to put plants where they will require no supplemental irrigation once established (a period of two to three years, depending on the plant and the situation). To understand what your garden has to offer, consider three important factors: light, soil type/moisture, and space availability.
Consider full sun anything greater than six hours of direct sunlight per day. Anything less than six hours is some variation of part shade to shade. Conduct a simple light analysis by observing light and shadow at least three times throughout the day, for example, at 8 a.m., noon, and 4 p.m. Soil can be a little more difficult to evaluate. Determine how well your site drains by conducting a percolation test. The simplest method is to dig a hole about 8 inches deep, fill it with water, let the water drain, and then fill it again. If it takes longer than 24 hours for the water to drain, your site is poorly drained; less than 12 hours, and your site is very well drained. Contact your local cooperative extension to conduct a soil analysis to determine your percentage of organic matter, soil texture, and pH. Finally, choose plants that at maturity will be the appropriate size for your garden. Avoid planting tall trees under power lines or putting aggressive spreading plants next to delicate, slow-growing specimens.
One final point: No matter what a plant’s cultural requirements, all new plants require care to establish in the garden. Treat newly establishing plants as if they are still in a container, providing ample water at least for the first growing season to make sure they get off to a good start.
MAINTAINING THE ECOLOGICAL GARDEN
The ultimate goal for the ecological gardener is a beautiful garden that provides year-round interest, supports local wildlife, absorbs and filters rainwater, and improves air quality. In other words, the ecological gardener thinks not just about creating and maintaining a beautiful garden, but also about the garden’s impact on environmental quality.
At Garden in the Woods, we practice some basic principles that ensure our garden stewardship contributes positively to environmental quality. First and most basic, we use native plants. They provide habitat for wildlife as well as a beautiful display for people to admire.
Second, we limit our use of irrigation water to new plantings. We site plants properly, matching their cultural needs to the right places in the garden so that we can turn off the irrigation water once the plants are established. As much as 30 percent of the potable water in New England is used for irrigating lawns and gardens. With droughts becoming more commonplace, it’s critical that we decrease that percentage, and siting plants properly is the simplest step in that direction.
Next, we never use fertilizers, focusing instead on building healthy, organic soils that provide all the nutrition our plants require. Fertilizers, even when used responsibly, are pollutants; they are highly mobile forms of basic elements like nitrogen and phosphorous that cause direct environmental harm to waterways. Fertilizer runoff leads to algal blooms and ocean dead zones, and the reality is that by recycling organic waste through composting and using organic mulches in our gardens, we have no need of fertilizers.
Finally, we never use pesticides. They can have disastrous unintended consequences to human health, as well as catastrophic environmental impacts. Systemic pesticides are absorbed by a plant’s vascular system, making the entire plant toxic to harmful and beneficial insects alike. The use of systemic pesticides has been linked to the decline of important pollinators, and their widespread use in growing plants for gardens means that many important pollinator plants are toxic to the very insects gardeners intend to support. When buying plants, always ask whether or not they have been treated with systemic pesticides.
Ecological gardening with native plants is a fantastic way to keep our gardens beautiful and make sure they support healthy, local ecosystems.
“Native Plants for New England Gardens” (© 2018 Globe Pequot, the flagship imprint of the trade division of Rowman & Littlefield) by Mark Richardson and Dan Jaffe will be released March 1. Preorder a copy or get the latest book tour dates at newenglandwild.org. Send comments to Address@globe.com.