Invasive Weeds in Our Watershed

Read the Articles:
Impacts of Invasive Weeds in Our Watershed (See below)
What YOU Can Do


The Impacts of Invasive Weeds in our Watershed

According to the California Invasive Plant Council, invasive weeds cost California $82 Million each year just for control efforts, monitoring and outreach. Estimates of actual impacts of invasive weeds reach into the billions of dollars. Invasive weeds are defined as non-native plants that are able to grow unassisted in our natural areas and have a negative impact on these places by causing economic harm, environmental harm or harm to human health. In California, invasive weeds interfere with ranching, farming, recreation, and habitat conservation.  The effects on our natural resources include: increased wildfire potential, reduced water resources, accelerated erosion and flooding, threats to wildlife habitat and degraded range and crop land.

There are several ways that invasive weeds are introduced and spread. Seed from invasive weeds can travel via wind, water, vehicle tires, clothing, and animal activity. Plants and seeds can travel across states and countries on automobiles, planes, trains and ships. Sometimes, invasive species are introduced purposefully and then they spread accidentally. An example would be a homeowner who unknowingly plants an invasive weed in their landscape. From that one plant, an invasion can begin through seed dispersion and/or underground shoots. Invasive weeds are able to thrive because they usually have no natural predators, they are very adaptable to new environments, and they grow and spread aggressively, outcompeting native species.

The first and best line of defense is to learn to identify these invaders so you can monitor for them and remove them immediately. Other strategies to control the spread of invasive weeds include being wary of what you plant in your landscape - never plant an invasive plant, working to restore native species populations, and sharing your knowledge of invasive weeds with family, friends, neighbors and local schools.

In the Colusa Basin Watershed, which spans the counties of Colusa, Glenn and Yolo, several invasive species have taken root. Of particular concern are the following (click on each for more information):

Giant Reed (Arundo donax)

Salt Cedar (Tamarisk ramosissima)

Perennial Pepperweed (Lepidium latifolium)

Yellow Starthistle (Centaurea solstitialis)

Barbed Goat Grass (Aegilops triuncialis)

Tree of Heaven (Ailanthus altissima)

Purple Starthistle (Centaurea calcitrapa)