Weed Management Techniques

Noxious Weeds

What They Are

Noxious weeds are more than plants out of place; they are non-native plants that are disrupting our native vegetation and ecosystems.

Noxious weeds threaten our drinking water supply, agricultural crops, pasture lands and native habitats.

Many of these plants come to Colorado as seeds in ornamental planting mixes, nursery stock or hitch-hike on the undercarriage of vehicles. Originally these plants have been transported from places as far away as Asia or Africa. Many of these species may still be sold in local nurseries for planting in landscapes.

Noxious weeds thrive because they have no natural controls, such as insects, and are able to adapt to varied climatic conditions. Some of these plants produce roots up to 15-20 feet deep and produce thousands of seeds annually.

Affects of noxious weeds are not limited to agriculture. Wildlife forage is being reduced or eliminated by this invasion as well. Additionally, some species reduce the water supply by individual plants consuming about 200 gallons of water daily. As good stewards of our land, be it a lot in a subdivision or a large acreage ranch, we all must work to keep our lands free of noxious weeds.

What do these weeds look like? (take a look at our "Enforceable Weeds" section for info and pictures)

Some are showy with beautiful flowers while others promptly fill in cleared areas. Some fill in niches or smaller voids in the landscape. Some weeds displace all other herbaceous plants and create a monoculture or single species stands. Using this web site will help to separate the invasive weeds from the native plants.

Flower color, annual or perennial growth, leaf shape and height are some of the characteristics used to assist in identification of the plants in question.

Q. What causes major weed infestations?  A. Detrimental Land Management Activities 

Some examples of detrimental land management activities that hinder grass plant health and set up scenarios for weed invasion are:  

  • Continuous grazing practices.
  • No grazing or no mowing practices.
  • Soil disturbance by off highway vehicles (OHV) or heavy equipment.
  • Accepting fill dirt with noxious weed seeds, concrete chunks, rock debris, sub soils or poor growing soils (shale, clay, etc). Adequate top soil is scarce in this region.
  • Grinding brush and not removing the wood chips during the operation.
  • Burning brush and trash piles on established grass meadows (scars heal slow, 5 to 8 years of intensive rehab required).
  • Continuous flood irrigation practices that drown out perennial grasses and promote Foxtail barley invasion.
  • Harboring burrowing rodents on property.
  • Natural debris flows following fire and flood.


Noxious weeds can be managed by using a combination of control methods including prevention, mechanical, cultural, biological, and chemical. 

Prevention involves planting weed free seed, mulching with weed free material, cleaning machinery before moving between sites and controlling weeds prior to their setting seed. Most important, it involves the use of land management practices that minimizes soil disturbance and compaction. It involves short duration, intensive grazing practices that takes half and leaves half of the plant un-grazed. It allows for enough time for plant recovery (re-growth) before more grazing is scheduled. It evaluates the health of a grass plant community and provides for sufficient nutrients and water to optimize plant health and growth.

Mechanical control involves mechanical methods, i.e.: shoveling, mowing, and cultivation. 

Cultural controls include over seeding with native plants or desirable grasses and a structured grazing plan. 

Biological control incorporates releasing beneficial insects which feed only on certain noxious weeds and well managed grazing practices that target specific weeds. 

Chemical control involves the judicious use of herbicides to compliment all control methods and provide an effective noxious weed management program. 

Above all, proper noxious weed identification, monitoring and consistent, diverse control methods can reduce or eradicate infestations. First off, learn how a weed spreads. If it spreads only by seeds, then take action to stop all seed production on an annual basis. If it spreads mainly by an underground creeping root system, then the proper timing application of an effective herbicide will be one of the most effective control methods in an integrated management approach.

Rehabilitation and Monitoring

The most important step is follow up and monitoring after controlling weeds or conducting rehabilitation work. Start a file and take photos with dates to record management activities failures and successes. Typical rehab time for perennial dryland grasses in the Southwest high mountain desert is 5 to 8 years on non-irrigated lands. Lands are fragile in La Plata County and disturbances or mismanagement generally comes with negative consequences.Recovery after disturbance or after weeds have become established requires thoughtful planning and and effective plan of action over several years time.