Steamboat Springs With our challenging climate, it's hard enough to grow desirable plants here. However, when aggressive, invasive, nonnative weeds insinuate their way into our yards and gardens, desirable flora and fauna suffer even more. Noxious weeds steal water and nutrients from native plants and boldly trespass onto ranch lands, river banks, neighborhoods and forests, becoming impossible to control. They rob vital food crops from ranchers, threaten wildlife, infest our forests and streams and displace native plants.
Matt Custer, the weed expert at the Routt County Cooperative Extension Office, says seven especially noxious weeds need to be eliminated from the Yampa Valley: leafy spurge, spotted knapweed, diffuse knapweed, Russian knapweed, dalmatian toadflax, yellow toadflax and whitetop, also known as hoary cress. Controlling noxious weeds such as these requires a combination of biological, chemical, cultural and physical methods.
Leafy spurge grows to 3 feet tall and has small yellow-green flower heads arising out of heart-shaped bracts and smooth, narrow leaves. When you cut the stem of leafy spurge, a milky substance will ooze, causing burning sensations to eyes and sensitive skin. "If horses and cattle chew this plant, it causes lesions in their mouths," Custer said. The seeds stay viable in the soil for up to 10 years.
Spotted knapweed has a lavender to purple thistle-like flower with black spotted bracts beneath the flower. It grows 1 to 3 feet tall with branched shoots and leaves that are narrow and deeply lobed in a rosette around the stem.
A tough competitor on dry sites, diffuse knapweed has one main stem about 18 inches to 2 feet tall with lots of branches. Its flowers are mostly white, sometimes purple, and are found on the branch tip.
Russian knapweed, very poisonous to horses, has unusual black roots that grow both vertical and horizontal. Flowers are thistle-like and colored lavender to white. The plant flowers in June to August.
Dalmatian toadflax and yellow toadflax both look like snapdragons (and, indeed, are close relatives) but are highly invasive. The dalmatian toadflax has a bright yellow snapdragon-shaped flower with an orange center on a 2- to 4- foot-tall stalk with waxy, heart-shaped leaves. Yellow toadflax, also called common toadflax, or butter and eggs, has a similar yellow and orange flower on leafy stalks 8 inches to 2 feet tall.
A member of the mustard family, whitetop, also known as hoary cress, is one of the earliest noxious weeds to emerge in the spring. It grows from 10 to 18 inches tall and has gray-white foliage with numerous small white flower clusters.
As gardeners, we need to maintain plant diversity by diligently managing infestations of noxious weeds before they truly get out of hand.
Deb Babcock is a Master Gardener through the Colorado State University Cooperative Extension office in Routt County. Questions? Call 879-0825 or e-mail email@example.com.