Why should we care about invasive plants?

The Boise Foothills and River Corridor support a variety of native plants and animals. Such biodiversity is threatened when a non-native plant species come to occupy these ecosystems. Non-native invasive species can alter the complex balance between plants, animals and soil that have adapted over thousands of years. In extreme cases, the ecosystems that once supported this balance can be eliminated by the introduction of non-native invasive species.

Weeds also have a significant economic impact. The damage they do on croplands, rangelands, wilderness and recreation areas, parks, and forests makes some of that land unusable for farming, grazing, logging, tourism, recreation, and housing, reducing the value of those lands. While some of that cost can be recouped through aggressive weed management, this too has steep costs. Studies at Cornell University suggest that the economic impact of invasive plants in the U.S. to be $120 billion a year. 

Weed infestations not only impair the quality of the landscape, but they actually increase the frequency and intensity of wildfires! Invasive plants threaten our forests, farms, and recreation areas, as well as our towns and our homes. In summary, they:

  • reduce biological diversity by crowding out native plants
  • compete with desirable plants for water and native pollinators
  • replace complex plant communities with monocultures
  • degrade wildlife habitat
  • clog streams and encourage flooding
  • increase soil erosion
  • blanket trails, walkways, lots, and landscapes

In the Boise Foothills, for example, cheatgrass has out-competed several native grasses and has grown into a blanket of grass covering much of the foothills. Cheatgrass burns easily and thrives after wildfire and, therefore, can replace grasses, shrubs and forbs that do not grow back quickly after fire. Our foothills, once supporting the sagebrush-steppe ecosystem, is now an invaded grassland ecosystem in many areas of the Boise Foothills. This shift in ecosystem causes significant changes in the composition, structure, and ecosystem function in our precious, public open space areas and beyond.

Non-native invasive species are often hard to control. They often require a mix of mechanical, chemical and hand removal efforts over several years to become successfully managed or eliminated. It is key to find and eliminate non-native invasive species when they are small, and remove them before they establish and propagate.

A typical non-native invasive plant will have some or all of the following characteristics:

  • high seed production
  • long-lived seed viability
  • hardy, far-reaching rhizomes (spreading roots)
  • ability to spread quickly via seed or roots
  • aggressive growth
  • ability to out-compete native plants 
  • toxic chemicals that suppress growth of nearby plants (allelopathy)
  • tolerance for disturbed or inhospitable growing conditions

These “weedy characteristics” enable invasive plants to spread—like wildfire! A few weeds spring up, then spread to cover huge areas if not stopped quickly. 

So what are some weeds common to our area? To learn more, click here