Don’t Plant a Pest

Some of the plants we purchase can escape to natural areas where they become a problem.

These invasives not only threaten our ecosystem, but they cost us money as well. Ever thought about whether any of the plants in your yard could be pests elsewhere? Just because they are not reseeding in our own yards and gardens doesn't mean they aren't causing problems in other places.

What is an invasive plant and how did invasives get here?

An invasive species is defined as 1) non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health.

Some invasives were introduced deliberately. Norway maple was brought to Philadelphia in 1756 by botanist John Bartram. Other invasives, such as Japanese stiltgrass, were introduced accidentally, often in packing materials.

What is it about Invasive plants that make them able to spread so widely?

Invasives:

can grow in many different conditions
are able to reproduce quickly by setting thousands of seeds. Some reproduce by roots and shoots
like disturbed conditions
because they are not in their native territory, have no natural enemies and can out-compete native plants
have a long flowering and reproductive season

I don't see them spreading in my yard. How do invasives get into our woods and natural areas?

Small seeds carried by long distances by wind & water (Examples: butterfly bush, Norway maple)
Berries eaten by birds who fly to natural areas and deposit the seed (Examples: Japanese barberry, autumn olive, privet)
Seeds hitchhiking on animals or hiker's shoes

Why are Invasives a problem?

They form monocultures and reduce diversity of our fields and forests
Invasives upset our food webs. Native insects can't eat plants they did not evolve with. Fewer insects mean less food for birds to feed their young.
Fruits of most invasives do not have the proper nutrition for our migrating birds
Invasives prevent new trees from sprouting in forests
Invasives can change the characteristics of the soil. (ex. Japanese barberry leaves raise the soil pH, making it unsuitable for our native plants)
Cost. From 2015 to 2017 Pennsylvania spent over $650,000 to control invasive plants.