Plant Invaders of Mid-Atlantic Natural Areas - National Park Service

What are native species?
A native species is one that occurs in a particular place without
human intervention. Species native to North America are generally
recognized as those occurring on the continent prior to European
settlement. Non-native (alien, exotic) species are ones that have been
introduced by people, from other continents, ecosystems, or habitats
to places where they don’t occur and would not likely have been
dispersed to by wind, water, wildlife or other natural means. Many
non-native plants have great economic value for agriculture, forestry,
horticulture and other industries and pose little environmental
threat. However, others have become invasive and are having a
serious and measurable ecological impact.
What are invasive species?
Invasive species are alien species whose introduction does or is
likely to cause economic or environmental harm or harm to human
health. Invasives often benefit immensely from arriving in new
places without the assortment of natural controls (e.g., herbivores
and diseases) in their native ranges that serve as a check on their
survival. Many also have one or more of the following: 1) adaptation
to disturbance; 2) broad tolerance for environmental conditions and
extremes of light, pH, and moisture; 3) production of large numbers
of seeds; 4) high seed germination success; and 5) ability to spread by
runners or rhizomes.
An infestation of garlic mustard (Allaria petiolata) displaces spring wildflowers.
Bill Johnson
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