Noxious weeds once thought to be beneficial

When good plants go bad... sounds like a book or movie title. When good plants go bad... results in some very expensive problems. When good plants go bad...is the basis for the launching of a new weed control effort.

Some plants, now listed as noxious weeds, were purposely imported for beneficial purposes. Kudzu and lespedeza were imported to provide soil cover for soil erosion control and as forage. Purple loosestrife, Cypress spurge, myrtle spurge, bouncing bet, Dyer's woad, and Dame's rocket were imported for gardening purposes. Russian olive and saltcedar were imported for horticultural purposes as ornamental shrubs or small trees.

You are probably wondering how a good plant goes bad. Introduced plants escape their natural enemies. Those natural enemies reduced their growth and reproductive capability in their native homes. Once released from their natural constraints, they can quickly become invasive in a new home.

Ecology is the study of the complex relationships found in nature. At first glance, a pasture, field, or forest seems like a simple mix of plants and animals. Upon close study, you discover a myriad of relationships exist. Each of these relationships can have from little to significant impact on the functioning of the ecosystem at that site.

We react to ecology with subjective evaluations. We might find a thick stand of Lodgepole pine trees to be beautiful and desirable in its mountain setting. A trip through the plains might elicit a response of "There is nothing out here!" Neither subjective view reflects the real ecology of those sites.

We also react to plants with subjective evaluations. A plant we find beautiful and desirable is a good plant. When we find a plant where it is not wanted, we call it "a weed." If that weed is particularly troublesome to control, it is "a noxious weed".

Purple loosestrife is a gorgeous flowering plant with glossy green leaves and purplish-pink flowers. It looks wonderful in a garden setting. When it grows in a wetland or riparian site, it becomes a noxious weed. In those sites, it quickly crowds out native plants and establishes a monoculture of loosestrife. This makes the site undesirable for waterfowl use. It changes the ecology of the site and reduces available waterfowl habitat. No wonder it is on our Colorado "A" list of noxious weeds.

Another beautiful plant is saltcedar, also named tamarisk. Saltcedar is a small tree or shrub that has reddish-brown bark and soft, green, needle-like leaves. It has pink flowers. It is on the Colorado "B" noxious weed list because it can take over a riparian or wetland area. Saltcedar crowds out native willows. The small tree pulls mineral salts from the soil and stores the salts in its leaves. When it sheds its leaves each fall, it causes a build-up of salts on the soil surface, which prevents other plants from growing in the vicinity.

Russian olive has silvery-green leaves, yellow flowers followed by white berries, and an interesting bark. It can crowd out native plants in wetland and riparian areas. It has spiny branches. Russian olive has very good survival in our difficult environment. When it replaces native willows, it reduces available habitat for wildlife and especially certain songbirds. This has earned it a place on the Colorado "B" list of noxious weeds.

Leafy spurge is relative of the Cypress and myrtle spurges. It can quickly replace grass in a riparian, pasture, or rangeland site. It reduces available grazing forage, unless livestock are trained to graze on it. The sap of the plant has a caustic effect. It also makes the Colorado "B" list of noxious weeds.

These four "good plants gone bad" are the reason for a cooperative weed management area (CWMA) becoming established. This area will cover the riparian corridor from the confluence of the Cache La Poudre River with the South Platte River to the Nebraska state line. The area is designated as the Lower South Platte CWMA.

A riparian corridor is the ecosystem adjacent to a stream course. For the South Platte River, a mix of cottonwoods, willows, and grasses characterizes the riparian corridor plant community. Some native shrubs and broadleaf plants are included in this natural plant community.

The purpose of the CWMA is to bring a concerted effort to the control of these four noxious weed species in that designated land area. The cooperative effort will share available resources and seek to find additional resources to assist and encourage all landowners in the riparian corridor to find, plan control efforts, and manage those species before they become a prohibitively expensive problem.

More information about the Lower South Platte CWMA is available from the county weed districts in Weld, Morgan, Logan, and Sedgwick counties. Local Conservation Districts and the Colorado Division of Wildlife are primary cooperators in this CWMA.

Date: 4/19/06

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