Midwestern Native Shrubs and Trees. Charlotte Adelman
native shrubs and trees enable birds to spend less energy foraging.32 Some migrating warblers time their spring return to the Midwest to coincide with the emergence of little-noticed and beneficial insects that, in turn, time their emergence to coincide with the new growth of native oak leaves.33 When required native host plants are too hard to find or unavailable, Lepidoptera will not reproduce. When native plants are readily available, more species, greater numbers, and healthier butterfly and moth populations occur. Reproduction rates corroborate this. On average, native plants support 13 times more caterpillars (larval stage of butterflies/moths) than nonnative plants.34 “Adaptation by our native insect fauna to plant species that evolved elsewhere is a slow process indeed.”35 To enjoy birds and butterflies within our lifetimes, we must plant natives.
For nesting birds, the importance of native woody plants cannot be overstated. Birds nesting in nonnatives such as buckthorn and honeysuckle are more likely to fall victim to predators such as cats and raccoons. This is due to characteristics like sturdier lower branches.36 Bird reproduction is controlled by food availability. Contrary to what many people believe, most “birds do not reproduce on berries and seeds,” Tallamy says, noting, “Ninety-six percent of terrestrial birds rear their young on insects.” For insects, including butterflies, to exist, they must lay their eggs on “host plants.” Butterfly caterpillars don’t eat most nonnative plants, which they find toxic, bad tasting, or tough, so butterflies rarely lay their eggs on them.37 Most butterfly caterpillars eat native host plants, and that is where the birds go to find them. “If you have a lot of trees that are not native, to the birds, it’s almost as if there are no trees at all.”38 Planting natives makes life easier for nesting birds to feed their nestlings. Comparisons done of production of the butterfly and moth caterpillar stage eaten by insectivorous birds demonstrate that Asian woody species produce a significant loss in breeding bird species and abundance.39 Don’t worry about birds eating all the caterpillars. When we create a diversity and abundance of native host plants, the resulting populations of caterpillars are more than adequate to sustain healthy populations of both butterflies and birds.
We associate hummingbirds with flower nectar, but they feed insects to their rapidly growing young, and the adult birds eat them too.40 Sunflower seeds entice cardinals to bird feeders, but they eat and feed insects to their nestlings.41 Chickadees, another popular visitor, almost exclusively feed their babies Lepidoptera caterpillars.42 “Regardless of the size of your yard, you can help reverse the loss of bird habitat. By planting the native plants upon which our birds depend, you’ll be rewarded with a bounty of birds and natural beauty just beyond your doorstep.”43 “Studies have shown that even modest increases in the native plant cover on suburban properties raise the number and species of breeding birds, including birds of conservation concern. As gardeners and stewards of our land, we have never been so empowered to help save biodiversity from extinction, and the need to do so has never been so great. All we need to do is plant native plants!”44 (For information on caterpillar productiveness of some important woody and herbaceous species see Selected Bibliography and Resources for Native Woody Species and Native Herbaceous Species in Descending Order of Lepidoptera Productivity.)
Modern landscapes are heavily loaded with male-only trees and shrubs, favored by landscapers because they are “litter-free.” Because male plants don’t produce fruits or seeds, they have long been considered to be desirable landscape plants. For allergy and hay fever sufferers, there is an unintended and unpleasant consequence. The very abundant, lightweight pollen produced by many male conifers and broadleaved trees is intended to pollinate the flowers of their female counterparts, but a lot is blown by the wind into people’s noses. “In contrast, a flower, tree or shrub pollinated solely by insects can be ruled out as an important cause of hay fever.”45 To prevent unneeded suffering, here is a tip. Don’t purposely plant male (pollen-producing) plants. Commonsense landscaping includes a good mix of naturally sexed native shrubs and trees. It also benefits wildlife because the buds, fruits, nuts, and seeds found on female trees are their food.
“As people learn the importance of native plants, they begin shopping for them. However, straight species are hard to find. Nearly every plant currently available is a cultivar of a native.”46 “‘Nativar’ is one term for a cultivar of a native species,” states the Wild Ones website. “Like all cultivars, nativars are the result of artificial selections made by humans from the natural variation found in species. Nativars are almost always propagated vegetatively to preserve their selected trait, which means they no longer participate in natural reproduction patterns that would maintain genetic diversity.”47 Traits they are bred or selected for include showiness, compactness, or resistance to a specific problem—but not all problems—as gardeners know who complain about poor performance.
Gardening with nativars is a risky experiment. Studies are under way, but the science is still in its infancy.48 “The biggest danger is that the nativar may interbreed with a local genotype, destroying and replacing the local genotype,” warns naturalist Sue Sweeney. “Interbreeding might turn a local genotype into a plant that the local fauna can not recognize as food, or, worse yet, into an invasive.”49 How nativars meet wildlife’s fundamental needs is an important subject that has not been widely explored. Some shortcomings are apparent. When scientific breeding changes leaf color (green leaf becoming purple or variegated), the leaf chemistry is undoubtedly changed. Variegated leaves in cultivars have less chlorophyll than solid green leaves and so are less nutritious for insects. Purple leaves are loaded with chemicals that deter insect feeding.50 A result is less insect food for nesting birds. An example is ninebark (see Spring Shrubs, p. 44). Selecting for height produces more lost food for birds. An example is ‘Gro-Low’ Fragrant Sumac (see Fall Shrubs, p. 242). Advertised for ornamental fruit, not all serviceberry nativars produce (see Spring Trees, Serviceberry Cultivar/Nativar Note, p. 78). At this time, only female inkberry nativars are commercially available.51 The female shrubs need a male to produce fruit, so birds go hungry. Sterile nativars are “bad news for goldfinches, who want the seed,” and doubled flowers are “bad news for pollinators, who can’t effectively reach the pollen and nectar.”52 An insect’s mouthparts can only pollinate plants with “a particular morphology” [form and structure of an organism or any of its parts], so “altering a flower’s shape might make it incompatible with pollinators.”53
Nursery industry marketing strategies call for frequently offering new, trendy nativars featuring different colors and shapes. What can a consumer do when nearly every plant currently available is a nativar?54 Patronizing native plant landscapers, nurseries, and plant sales, and being selective when visiting generalist purveyors, are ways to overcome these challenges. Midwesterners can create gardens, yards, and communities composed of true native plants.
The idea of restoring all of North America’s ecosystems to a pure, pre–European immigrant state is unrealistic. But perfection is not required. Recognition of the fundamental connection between native plant species and wildlife is essential. This insight leads to pitching in and planting native species in areas over which we have unique control (yards, gardens, condominium balconies). Choosing natives is a practical, direct, and enjoyable way to help wildlife and achieve immense good. To our readers we say, before planting a shrub or tree, think about the beauty and the environmental benefits provided by our true native midwestern woody species.
Each gardener and landscaper should decide on the pace at which to convert to native shrubs and trees. Substituting natives for nonnative species need not require a drastic overhaul of a garden. Homeowners may choose to proceed gradually, adding or replacing nonnative shrubs and trees as they decline or die. Some may opt to do it themselves, others to employ a professional native plant landscaper, or some combination of these approaches. Going at one’s own pace is essential to achieve the most joyful and ultimately successful results. Before you start planting and rearranging, consider the essential items (cover, food, water, reproduction) for birds and butterflies, and plan so that you use