Unless you're a specialist plant collector, you probably choose landscape plants on what is appealing to you in flower or foliage, or both. For most, cost also is a factor. Increasingly gardeners want landscape plants that are sustainable-- no significant problems, not invasive, drought tolerant once established, low maintenance, and long-lived. To be sustainable, plants must be matched to their site, or "right plant, right place". Otherwise plants may grow poorly, need lots of care, or worse, die off.
So once you find an appealing landscape plant, consider where it will be planted. A bit more planning up front pays off with longer lived, more healthy plants, and much less labor later. Here are 10 main factors in matching a plant to its future home, and to your needs and resources, in order for it to be sustainable.
- Hardiness. If you don't know what hardiness zone you live in, get familiar with this (books, online, and store personnel can help) and see if it matches your plant choices. Keep in mind there are small climate variations on most properties-- microclimates-- that can be warmer or colder. Consider these when finding sites for new plants.
- Height and width. Find a space of suitable size for your plants when they are mature. This will keep you from excessive pruning, or having to relocate them when large and hard to dig.
- Sun exposure. Determine if your plant prefers sun or if shade, how much. And will it tolerate the opposite?
- Soil pH. Does your plant need a certain pH or soil acidity, or will it do well as most do in a slightly acid soil? What is your soil pH? If you don't know, inquire at your garden store about soil testing and kits, or from your local Extension office.
- Soil type. Is your soil well-drained? What does your plant need, or at least tolerate? Also consider whether your plant will tolerate a soil extreme if you have such, like sand or clay.
- Drought. Once the plant is established (water well the first year after planting), will it tolerate drought? If so this will save you on the time and expense of watering often.
- Growth habit. This could be thought of in terms of plant shape, also in terms of its behavior. If you want a rounded plant, buy one with a rounded shape unless you want to spend lots of time shearing. Is the plant "vigorous"? (This is often a term on labels and in catalogs for aggressive spreaders that will overtake a bed and may become invasive even beyond.) If so, do you have a site where it can be contained? (Pavement such as walks and walls contain spreaders well.)
- Pests and diseases. Check to make sure your plant doesn't have serious problems with these, or can tolerate them (such as powdery mildew on garden phlox). If it can tolerate a disease, can you tolerate the looks of it aesthetically?
- Maintenance. This relates more to your own time and resources. Will your plant require frequent pruning, fertilizing, deadheading (nipping off) old flowers, staking, or similar?
- Longevity. Is your plant long-lived, or will it die out (such as the biennial hollyhock or short-lived delphinium), or need digging and replanting or dividing every couple years (such as some coralbells)?
In addition to considering these factors for each plant, consider a couple others for your plants to make your whole landscape sustainable. Use a diversity of plant choices, the more the better. This not only makes a landscape more interesting, but helps beneficial insects and pollinators, and avoids big loses should harmful insects or diseases invade. A diverse plant palette also will be more beneficial to wildlife. Choose plants to provide shelter and food. Many gardeners start their choices with native plants, but don't overlook others that may fit these needs.
For deciduous trees (those that lose their leaves in winter), consider for smaller trees the crabapples (look for disease resistant cultivars), three-flowered maple, Japanese tree lilac, and native river birch and American hornbeam. For large deciduous trees consider the native American hop-hornbeam, sugar or red maple, American yellowwood, American beech, oaks, silverbell, and larch. Large non-native trees include the ginkgo, katsura tree, and Japanese zelkova. Evergreen trees for sustainable landscapes include white pines, spruces, and arborvitae.
For evergreen shrubs, consider the eastern red cedar or junipers (disease resistant species and cultivars). Deciduous native shrubs include the bottlebrush buckeye, fothergilla, red chokeberry, inkberry, winterberry, summersweet clethra, sumacs, and highbush blueberry. Deciduous non-native shrubs include 'Miss Kim' and 'Palibin' lilacs, as well as shrub dogwoods.
There are many perennials to choose for sustainability. Some non-natives include feather reed grass, 'Rozanne' perennial geranium, bigroot geranium, daylilies, and sedum. Native perennials include false indigo, bluestars, 'Moonbeam' coreopsis, coneflowers, joe-pye, switchgrass, black-eyed susan, little bluestem grass, bugbane, phlox, and foamflower.
More choices for sustainable landscape plants, including ones resistant to some specific major pests, can be found in a factsheet by Deborah Swanson from University of Massachusetts Extension ( www.umassgreeninfo.org/fact_sheets ).