NPS photo

Canada thistle is a common weed problem at park sites in Montana, Idaho, and Oregon.

Invasions of exotic species represent one of the most serious threats to natural ecosystem integrity. Biological invasions are occurring at accelerated rates in nearly every major ecosystem. Invasive nonnative plant species are of concern given their ability to quickly expand into new areas, compete with and exclude native species, and alter ecosystem processes. At Nez Perce National Historical Park, invasive plants, most of which are nonnative species, pose one of the greatest threats to natural and cultural resources and havebeen identified as a high priority management responsibility.

“Weeds” can be defined in many ways. To the average person, the term “weed” refers to:

·         A plant growing where it is not wanted,

·         A plant out of place,

·         Plants that are a nuisance, unsightly, or harmful, and/or

·         A plant whose virtues have yet to be discovered.

Although there is truth to all these definitions, these statements minimize the impact of weeds on humans and the environment and disregard some fundamental biological features of weeds that set them apart from most other plants. Weeds are what they are because they have certain characteristics that make them different from other plants.

NSP photo

Poison hemlock often occurs near pastures and cropland and is present throughout much of Idaho. All plant parts are poisonous.

The following is a list of “weedy characteristics,” many of which are possessed by the worst weeds in the world.

·        Parasitic on crop plants

·        Poisonous

·        Reduces crop value

·        Hosts for diseases and other pests

·        Block waterways

·        Hinders the functioning of equipment

·        Affects manmade environments other than agricultural land

·        Socially unacceptable (i.e., marijuana, poppies, etc.)Directly interferes with crops and other plants

It is also important to keep in mind that when a plant is not desired, it still needs to be managed or “controlled.” Even ignoring a weed (i.e., no action) is actually a management technique, as defined in NPS policy.

Park staff are making a concerted effort to locate, identify, and treat these weeds with proven Integrated Pest Management procedures. This is important to guarantee that federally and state listed noxious weeds and other nonnative species do not gain a foothold and then replace the native plant communities found here.