Action 1. Remove Invasives and protect native plant communities

The legal definition of an invasive species, and the official position of the U.S. government, is "An alien species - not native to the ecosystem - whose introduction does or is likely to cause economic or environmental harm or harm to human health." ("Alien" refers to species not native to the ecosystem).

An invasive species can be any kind of living thing--a plant, fish, insect, fungus, bacteria, or even the eggs or seeds of an organism-- that does not naturally occur in a specific area. By far most people encounter invasive plant species that endanger pollinator habitat and are an increasing problem in Pennsylvania.

Why are invasive species so bad for the ecosystem?

  • Out-compete native species for food or other resources
    (Example: Japanese barberry (Berberis thunbergii) alters microbial activity in soils, increases soil pH, and reduces forest leaf litter.)
  • May cause or carry disease that affects the health of native species
    (Example: Hemlock woolly adelgid, an insect pest from Asia, kills eastern hemlock trees.)
  • Contribute to the decline of threatened and endangered species
    (Example: Feral pigs forage aggressively for insects, plants, small birds, amphibians, reptiles, fruits, nuts, and berries.)
  • Prey on native species or prevent them from reproducing
    (Example: Norway maple from Asia and Europe seeds prolifically and produces dense shade preventing native species regeneration.)
  • Change entire food webs, decreasing biodiversity
    (Example: Purple loosestrife chokes out waterways by creating a monoculture.)

Did you know that out of the 50,000 introduced plants in the United States nearly 5,000 are wreaking havoc on our environment? Invasive species are second only to habitat destruction, such as by fire or land clearing, for displacing native plant and animal communities and altering entire ecosystems. Some invasive plants have been introduced accidentally, one example is mile-a-minute (Persicaria perfoliata) that is prolific in disturbed habitats; some species were introduced for wildlife benefits such as multiflora rose (Rosa multiflora) and Japanese honeysuckle (Lonicera japonica); or for erosion control like Japanese knotweed (Fallopia japonica); or for medicinal and/or food use such as garlic mustard (Alliaria petiolata). Others have escaped from our gardens like purple loosestrife (Lythrum salicaria), a Pennsylvania noxious invasive plant that devastates waterways. Once they establish in natural areas their ability to propagate in several ways and to thrive in many conditions allows them to spread rapidly. Because they have few or no natural enemies in their new home they can usually out-compete native plants. This upsets the delicate balance of local ecosystems and affects the insects and pollinators dependent on the natural habitat.

Some common garden plants that are on the invasive list are:

  • Japanese Barberry (Berberis thunbergii)
  • Burning Bush (Euonymus alatus)
  • Autumn Olive (Elaeagnus umbellata)
  • Privet (Ligustrum sp)
  • Bush Honeysuckles, Tartarian, Amur, (Lonicera sp.)
  • Oriental Bittersweet (Celastrus orbiculatus)


Japanese barberry invades a Pennsylvania forest

oriental bittersweet

Oriental bittersweet swallows white pine trees in a York County park

Another imported plant that is showing up on invasive lists is Buddleia davidii, better known as Butterfly Bush. It has been escaping to roadsides and natural areas in the Mid-Atlantic region and has the potential to displace important butterfly host plants.

Buddleia image

Butterfly bush invades habitat along Rt 83

What can you do?

  • Avoid buying and planting invasive plants in your landscape. Be selective and research your plants prior to purchasing them to ensure you select native and/or non-invasive plants for your landscape.
  • Identify existing invasive plants on your property and initiate a plan to remove them. If you have a woodlot or meadow on your property remove any invasive plants and protect existing populations of native plants.
  • Where invasive plants are removed, replant with native plants or seed in native plants as soon as possible.
  • Learn to identify and manage invasive plants by helping at your local park, preserve, or other natural areas with knowledgeable volunteers and/or experts in the field.

For more information and list of invasive plants in your area, click on the publications below:

In order to certify, the following is required of your garden:

  • Avoid acquiring invasive ornamental plants
  • Develop a plan to actively remove and/or avoid use of invasive plants

Continue to Step 4: Safeguarding Pollinator Habitat (Part 2)