Rio Grande County Weed District


Summer hours (May to Sept)- 7:00 am to 5:00 pm Mon- Fri
Winter Hours (Oct- April) - 8:00 am to 4:00 pm Mon - Thursday
Closed on weekends and major holidays

Brianna Brannan
0164 W county Road 3 North
Monte Vista CO 81144

Cell: 719-580-0089
Phone: 719-852-4804

Bad, but beautiful Noxious Weeds

Job Openings within the Rio Grande County Weed District

If you are interested, please download and apply for the following:


          The application    


Russian Knapweed
Russian Knapweed
Russian Knapweed develops on many soil types, is very drought tolerant and is known to have allelopathic properties. Russian Knapweed is reported to have lethal effects on livestock due to its uptake of Zinc in the soil. The plant reproduces primarily through root system and fragments of one inch or less can reproduce into a new plant from depths of six inches. Russian Knapweed also reproduces via seed in small quantities, survival of seeds are from 3 to 5 years in soil bank, and new growth by seed is uncommon.
Black Henbane
Black Henbane
Black Henbane is an annual / Biennial with a long tap root and reproduces only by seed, but produces approximately 100,000 to 500,000 seeds per plant. Seeds are known to last approximately 5 years in the soil. Black henbane is an opiate and all parts of the plant are poisonous andpotentially lethal to humans and livestock. The plant and seeds have been used as a hallucinogenic and theflowers and give off an odor that causes a kind of “high”.


Land owner Info

All noxious weeds on your porperty must be visually (mown or sprayed) controlled BEFORE FLOWERING STAGE.

If you are a "Sensitive Person" to herbicides, you must register at: 

ALSO, you are still responsible for controling the noxious weeds on your property.

What we do

Rio Grande County Weed District is one of the only true "Weed Districts" in the San Luis Valley that is operational. Operational meaning, the weed district supervisor contacts those with private land containing noxious weeds and provides resources and weed managment plans to assist with meeting the control requirements set forth by the State of Colorado, and benefit for not only the land owner but for the whole of the county.


The Rio Grande County Weed/ pest District was formed by the request of local farmers who were concerned with the health and economics of the agricultural lands within the county due to the invasive noxious weeds. In 1963 the county was split in three noxious weed control districts. In 1970 the three districts merged into one weed and pest district for the service of all Rio Grande County. During the same year the State of Colorado issued the Noxious Weed Act which defined that,  "Noxious weeds have become a threat to the natural resources of Colorado, as thousands of acres of crop, rangeland, and habitat for wildlife and native plant communities are being destroyed by noxious weeds each year." 35-5.5-102. Legislative declaration(1.5)(a) To this day Rio Grande County Weed District strives to control noxious weeds through intergative processes and partnering with other entities.  

Resources used

Montana University Extension:

DiTomaso, J.M., G.B Kyser at al. 2013. Weed Control in Natural Areas in the Western United States. Weed Research and Information Center, University of California.

Colorado State University:

Colorado Department of Agriculture:

Whitson, T. (2006) Weeds of the west. Jackson, WY: Grande Teton Lithography

Merrill A. Ross :

Effective Control of Noxious Weeds

Canadian Thistle

Mowing – is effective if mown every 20 days for the full growing season for several seasons
Grazing- In the spring with fall application of herbicide
Herbicide- Is effective for thistle eradication, but only if followed by these specific steps:
  1. 2,4-D in the spring to keep from flowering
  2. Application of Translocation herbicide with sticker adjuvant in fall
  3. Repeating this for at least three years
  4. Reseeding in Fall the second year of control to re-establish desired grasses and/or forbs