Pennsylvania Native Species Day, designated by the Governor’s Invasive Species Council, is being celebrated on May 16.

Comprised of seven state agencies and 14 different partner organizations whose members include representatives from environmental advocacy groups, agriculture, industries and local governments, the council selected the day to promote awareness of all native species found in Pennsylvania, including plants. Pennsylvania Native Species Day also serves to expand public recognition of the increased threat of invasive species.

Penn State University defines an invasive plant as one that grows aggressively, spreading and displacing other native plants in an ecosystem, such as one's yard or property. Under certain conditions, invasive plants can become the dominant species and alter natural habitats.

The expansion of the global movement of goods and people have created travel routes for non-native plant and animal species. In Pennsylvania, the Invasive Species Council has identified 140 species of plants considered invasive. Managing or removing invasive species can be expensive and time consuming.

Penn State University uses the term invasive to describe a plant that grows rapidly, spreads aggressively and displaces other native plants. They are non-native to the area but have naturalized and negatively affect the ecosystem they inhabit. Invasive plants degrade native environments by causing a decline in native plant species diversity.

Many of us have seen swaths of English ivy (Hedera helix) and stands of Norway maple (Acer platanoides), Japanese honeysuckle (Lonicera japonica) and orange day lilies (Hemerocallis fulva) in surprising places during our travels throughout Pennsylvania. These plants often originated in home gardens and spread into other habitats.

Native plants are the best choices for our home landscapes. They have evolved to grow in our existing soils and weather conditions, are easy to care for, and may be more disease and stress tolerant compared to non-native plants.

Additionally, native plants can support the life cycles of important pollinators and wildlife. Planting non-native species does not typically yield similar wildlife or pollinator values that native species do. Substituting native species for invasive species can provide the same desired design outcome in our landscapes.

Whether we wish to plant ground cover or use trees and shrubs for privacy screening, native plants are a logical choice. More native plant species are available in garden centers. Professional landscapers are embracing native plant species as the native plant movement gains popularity with homeowners. If you are contemplating creating or renovating your landscape, celebrate native species by purchasing plants native to Western Pennsylvania.

Here are a few suggestions for substituting native ground covers, perennials, shrubs and trees for invasive ones.

√ English ivy is often found as an evergreen ground cover. The same evergreen effect can be achieved by planting wild ginger (Asarum canadense), with the added benefit of supporting insect pollinators. Trumpet honeysuckle (Lonicera sempervirens) is a wonderful substitute for another invasive vine, Japanese honeysuckle. Your reward will be visits from hummingbirds and butterflies, when flowering, and birds feasting on the fruit.

√ The bright, showy flowers of the orange daylily can be difficult to manage. The orange daylily is often seen along roadsides and ditches, where it has invaded from original garden plantings. Replace orange day lilies with Canada lily (Lilium canadense) or wood lily (L. philadelphicum), both of which have showy orange flowers and support pollinators including bees, butterflies and birds.

√ Replacing Japanese spiraea (Spiraea japonica) with steeplebush (Spiraea tomentosa) or nine bark (Physocarpus opulifolius) attracts pollinators. Their exfoliating bark provides winter interest to the landscape.

√ The beautiful fall color of burning bush (Euonymus alatus) can be replaced with high bush blueberry (Vaccinium corymbosum), and you can enjoy your own fresh blueberries in season!

√ The native red maple (Acer rubrum) is an excellent substitute for Norway maple (Acer platanoides).

√ Bradford pear/Callery pear (Pyrus calleryana), the flowering tree with somewhat malodorous but showy white flowers, is found in many business parks and home landscapes. Consider replacing this species with flowering dogwood (Benthamidia florid, formerly known as Cornus florida) or serviceberry (Amelanchier spp.). Both of these native species contribute showy white spring flowers and fall color to the landscape while attracting pollinators and birds.

Landscapers and homeowners might be confused on which native plants to substitute for commonly sold invasive ones. The Pennsylvania Native Plant society offers native substitutions for invasive plants. Visit their website at panativeplantsociety.org for more information.

Penn State Extension lists native substitutes for invasive plants at extension.psu.edu/programs/master-gardener/counties/york/native-plants/fact-sheets/native-replacements-for-invasive-plants.

Penn State has updated information on invasive plants at ecosystems.psu.edu/research/centers/private-forests/news/announcing-new-invasive-plant-fact-sheets-series.

If you have questions about substituting invasive plants with native plants, call the Master Gardeners of Butler County Garden Hotline at 724-287 4761, ext. 7, or email the Master Gardeners at butlermg@psu.edu.

Mary Alice Koeneke is a Penn State Extension Master Gardener of Butler County.

Mary Alice Koeneke