Native plants are disappearing. Many pollinators are at risk of disappearing. Building and land development are causing habitat loss.
Climate change is a real concern that is affecting many aspects of the natural world. Invasive species are crowding out the plants pollinators need to survive.
These factors alone or in combination can result in plant and pollinator species becoming so rare that they are placed on an endangered species list or are lost (extirpated) from all or a portion their former area.
The state Department of Conservation and Natural Resources reports that about 3,000 native plant species grow in Pennsylvania. Of those, 228 are endangered; 78 are listed as threatened; and 106 species are considered extirpated.
When it comes to information about declining native plant and wildlife populations, gardeners hear from a variety of sources. It’s difficult to sort out what all this means, especially for gardeners who want to do their part to support native pollinators and wildlife.
Doug Tallamy, Ph.D. entomology, a professor of entomology at the University of Delaware and author of Bringing Nature Home, has demonstrated that native insects and wildlife co-evolved with and are dependent on native plants. When native plants are pushed out by invasive species, the native insects and wildlife lose their food sources. We lose the natural diversity of species.
Some invasive plants are introduced accidentally. Bradford/Callery Pear (Pyrus calleryana) and Japanese Barberry (Berberis thunbergii) were used extensively in landscapes before scientists and land managers recognized their invasive habit.
Crown vetch (Securigera varia) and kudzu (Pueraria montana) were introduced for erosion control; both have been proven to crowd out native plants. Changing climate conditions have allowed species like kudzu, which started out in the South, to move north.
The presence of native trees, shrubs and perennials returns native biodiversity, naturally increasing the species of insects, birds and other wildlife in our yards. Planting white oak (Quercus alba), red maple (Acer rubrum), and shagbark hickory (Carya ovata) provides habitat and food for caterpillars.
Tallamy’s research has shown that one white oak tree is capable of supporting 534 species of caterpillars. Caterpillars are not only the larval stage for moths and butterflies; they also feed many of our native birds, especially during the nesting season.
In contrast, according to Tallamy, the invasive Bradford/Callery Pear is a popular tree that is inexpensive and easily available; however, they are not only invasive but are toxic to wildlife that try to eat them.
Being familiar with related terminology can help gardeners faced with planting decisions. The following definitions are those generally accepted by environmental professionals.
Conservation is the preservation, protection, or restoration of the natural environment, natural ecosystems, vegetation, and wildlife.
Native plants have been defined as those present at the time Europeans arrived in North America.
Endangered species are those threatened by extinction throughout most of their natural range.
Threatened species may become endangered if their habitat is not maintained to prevent future decline.
Extirpated species are believed to be extinct within a defined area like a county or a state. They may or may not be found outside that defined area.
Non-native/alien/exotic plants are those not considered native. They may or may not be invasive.
An invasive species is a plant whose introduction does or is likely to cause economic or environmental harm. Invasives “hog” all the space and resources, crowding out native plants.
What can we, as gardeners, do to support native pollinators and wildlife and help to maintain a diversity of species?
Home gardeners can help in conservation efforts by planting native plants that, in turn, provide food sources for native pollinators and wildlife. They can remove or refrain from installing plants that have proven invasive. Here are some suggestions for planting native species:
Looking for a spring flowering tree? Consider natives such as flowering dogwood (Cornus florida), sweetbay magnolia (Magnolia virginiana) or serviceberry (Amelanchier arborea) instead of Bradford pear or Japanese cherry (Prunus serrulata).
Want vines for a trellis? Try American bittersweet (Celastrus scandens) or limber honeysuckle (Lonicera dioica) instead of Oriental bittersweet (C. orbiculatus) or Japanese honeysuckle (L. japonica), both of which are very invasive.
Planting a hedgerow? Japanese privet (Ligustrum japonicum) and burning bush (Euonymous alatus) are both regarded as invasive. Instead, consider American holly (Ilex opaca) which has the added bonus of being evergreen and produces berries for birds.
When planting perennials, choose native species such as butterfly weed (Asclepias tuberosa) or swamp milkweed (A. incarnata), New England asters (Symphyotrichum novae-angliae), and woodland phlox (Phlox divaricata).
When shopping for plants, buy nursery propagated native species; do not collect plants from the wild. Avoid invasive plant species (Pennsylvania maintains a list on their website: www.dcnr.pa.gov/Conservation/WildPlants/InvasivePlants).
If you have additional questions about native plants, call the Garden Hotline at 724-287-4761, Ext. 229.
Mary Alice Koeneke, a Penn State Extension Master Gardener of Butler County, retired as a biologist for an engineering and consulting firm after 35 years. Susan Struthers has been a Master Gardener since 2004.