Manage Noxious Weeds
Noxious weeds are defined as plants that are one or more of the following:
•aggressively invade or are detrimental to economic crops or native plant communities
•are poisonous to livestock
•are carriers of damaging insects, diseases, or parasites
Leafy Spurge: Chemical treatment is recommended. Mechanical treatment is not recommended due to extensive root system.
Where do weeds come from?
Noxious weed seeds are dispersed by wind, water, and animals. Seeds can also be spread by mud attached to vehicle tires, or by attaching themselves to people’s clothing. Soil amendments, animal manure, and commercial seed can also be contaminated by noxious weed seeds. Because of these constant dispersal mechanisms, permanent weed eradication is unlikely, especially over large areas; this is why annual weed control is necessary.
A professional contractor sprays herbicide onto noxious weeds. The herbicide is mixed with blue dye, which helps the contractor keep track of which weeds have been sprayed.
Common Mullein: Uproot by hand or shovel. If flowers have developed, cut off stalks, bag and dispose to prevent seed dispersal. Larger infestations may justify herbicide use.
Disturbance creates opportunity.
A disturbance is anything that moves existing soil or uproots existing plants, such as forestry work, construction, excavation, tillage, flooding, or erosion. Once noxious weed seeds are present, they can remain viable in soil for decades, and only sprout once a soil disturbance provides an opportunity by eliminating competition from other plants.
Noxious weeds replace native species.
Without natural predators such as insects, fungus, and animals to keep them in check, noxious weeds can outcompete native plants and colonize huge swaths of land. Noxious weeds damage wildlife habitats. Invasive noxious weeds rapidly upset the balance of the local ecosystem, depriving wildlife of the food and habitats they depend on.
Weed management is long-term.
There is no quick fix to most noxious weed
infestations. Permanent eradication of all
noxious weeds on your property is usually not a realistic goal, except in small, focused areas. A landowner's focus should be to suppress noxious weeds so that they don’t get out of control. This is an ongoing process and should be part of a property's regular maintenance every year.
Noxious weed control methods include:
•Prevention: Keep weeds from hitch-hiking a ride onto your property by checking your boots, clothing, vehicles, and pets for seeds before returning home from hiking, camping, or driving off-road. Use state-certified weed-free soil amendments, forage, and seed.
•Cultural: Keep native vegetation on your property healthy and minimize soil disturbance. Establish native vegetation on any bare ground areas to outcompete noxious weeds.
•Physical: Hand-pulling, digging, cutting
flowering heads, mowing and weed-whacking are options for most of the annual and biennial noxious weeds before they can produce seeds.
•Chemical: Herbicides are the only realistic control option in many situations, particularly with deep-rooted perennials. There are many modern herbicides that are non-toxic to animals and pollinators when used as directed.
Canada Thistle: Chemical treatment is recommended. Mowing can be effective if done every 10-21 days. Pulling or tilling will make infestation worse.
Who can perform noxious weed control?
•Do-it-yourself: Many small infestations are treatable without expert help. See the Colorado Department of Agriculture’s weed fact sheets for recommendations. When using herbicides always adhere to the directions in the product label. The label is the law!
•Hire a contractor: Licensed private contractors are available for you to solicit and hire. Herbicide application is the most common control method provided by contractors.
Treatment is required by law.
Protecting our natural resources and agricultural lands is critically important in Colorado and required by law. Make a plan to control the noxious weeds on your property to comply with local laws and the Colorado Noxious Weeds Act. See your county’s noxious weed list on the CDA website for local management goals.
Yellow Toadflax: Chemical treatment is recommended. Mechanical treatment is not recommended due to the extensive root system.
Musk Thistle: Uproot by hand (wear gloves) or shovel. If flowers have developed, cut them off, bag and dispose to prevent seed dispersal. Larger infestations may justify herbicide use.
Need help with weed ID or weed control?
Visit these websites for lists and photos of weeds in your areas: