Expand/Collapse All

For information about native and noxious weeds, where can I go?

Who can I hire to spray my weeds?

Where can I learn more about herbicide affected compost?

"No Spray" - How can I list my property as "No Spray"?

    If you have a parcel which is in front of a county road you can call 382-6470 and list it as a no spray property.  If the county isn't responsible for eliminating noxious weeds in front of your property, you must be.  Only list A and B weeds need to be controlled.  You must dig up or mow any applicable weeds before they go to seed.  If proper weed management is not done on county road right of way, the county must resume spraying there to comply with the Colorado Noxious Weed Act, C.R.S. § 35-5.5-101.  If you have property in front of a state road you must contact CDOT.

    If you have an organic farm or pesticide sensitive crops you can register at driftwatch.org.  This is an official database in which your name and address is logged.  You will also be sent signs which are highly visible and much more effective than a homemade "No Spray" sign.

What should I do with herbicide I no longer need?

    The County Weeds Dept. cannot accept herbicide donations at this time.  The County sponsors a Household Hazardous Waste Collection event in even numbered years. This information will be updated as possible.

What kind of herbicide should I use and when do I spray?

    There are different herbicides for different types of weeds.  Our information sheets (choose type and then follow link to info sheet) for each enforceable species gives several recommendations for herbicides as well as the ideal time for spraying.

What are Invasive Ornamentals?

    There are several noxious weeds that have attractive looking flowers, but are highly invasive. These "escaped ornamentals" were introduced as flowers for gardens or as part of wildflower mixes and can spread rapidly. Oxeye daisy has white petals with a yellow center and is often confused with wildflowers. Myrtle spurge and Cypress spurge (both have yellow flowers) are often found in planters and escaping/spreading into nearby soil. Yellow toadflax has a snapdragon flower and can be mistaken for an ornamental or wildflower, and can grow at higher elevations above timberline. Absinth wormwood is a sage looking plant with small yellow flowers that appear late in season, and has been used for landscaping because of its ability to flourish with very little water.

How do I report problem weeds?

    • If your neighbor or a landowner has a significant weed problem*, the Adjacent Land Form can be filled out
      (Must be a valid infestation and positively identified).   
    • For county roads, use the County Roads Form.    
    • For State Highways, US Forest Service, towns or municipalities contact them from this directory

    *These weeds need to be correctly identified and on the mandatory and enforceable list.  Each weed is listed and more details can be found under the fact sheet.

Does the "Herbicide Cost-Share" program still exist?

Unfortunately no. 

Due to budget cutbacks the County discontinued this program.  It is uncertain if this program will be reinstated in the future.

What weeds can be controlled effectively by hand pulling or digging?

  • Mowing does not have the same effectiveness as hand pulling or digging.
  • Hand pull or dig when soil is moist.
  • Hand pull or dig before flowering occurs, usually around June or July.
  • If removed during or after flowering, bag and dispose of plants carefully so you will not scatter seeds.

Absinth wormwood- Make certain to pull all the roots, including short horizontal roots.

Musk, Scotch, Bull thistles- Cut tap root two inches below ground to prevent re-growth.

Houndstongue- Cut taproot two inches below ground to prevent re-growth.  Old seed stalk:  Prior years dead plants with hanging seeds can be carefully cut at the bottom of the stalk then bagged.

Spotted knapweed- Be sure to hand pull or cut taproot at least 5 inches below soil to prevent re-growth before flowering and seed formation.

Oxeye daisy and Scentless chamomile - (recommended for new or small infestations) Hand pull or dig when soil is moist.  Oxeye is fairly shallow rooted- make sure to pull up all of the roots.

Myrtle and Cypress spurge- Make certain to pull all the roots.  Be careful and wear rubber gloves and eye protection, as the milky sap is caustic.

What kind of thistle do I have?

There are 3 main thistles in La Plata County. Scotch thistle is very big and spiny with large gray/green leaves and large purple flowers. Musk thistle is tall, but have darker and smaller green leaves/stems with symmetrical leaves. They have single pinkish/purple flower heads.  Canada thistle grows relatively shorter but in thicker stands, and have clustered seed heads with multiple, small pink flowers.  Canada thistle is prevalent near waterways, such as riversides, irrigation canals, fields and ponds, although it can also be found in dry sites.  Bull thistle has a unique leaf shape, which is narrow, spine-tipped, and progressively narrower at the tip.  The leaves are also dark green and have fine hairs.  Scotch, Musk, and Bull thistles are all biennial; meaning the first year the plant is a small rosette, without flowers.  The second year the plants produces seeds via flowers then die.  Canada is a perennial, meaning it lives year after year.

Is mowing an effective way to control weeds?

For the most part, no.  Mowing can actually increase shoot density of some plants with a creeping root system.  Research has shown that several mowings on Canada thistle will introduce stress and set up the plant for a fall-applied herbicide.

After being cut, most weeds will re-grow shoots from the reserves in the roots back into the upper plant in order to make flowers and seeds.  Certain plants can even create multiple stocks or heads where one was cut off, thus increasing the seed count.  When controlling a bi-annual seed production plant, like Musk thistle, the root should be cut one to two inches below soil surface prior to flowering, which will kill the plant.  Preventing flowering and seed formation is critical for success for plants that only spread by seed.

Some studies have shown that after years of repeated mowing at the right time can eventually exhaust a plants reserve in the root system.  However this is not recommended unless you plan on mowing multiple times a season.

Is tilling an effective way of controlling noxious weeds? 

Not unless you have annual or bi-annual seed producing plants, and till before they produce seeds.  Tilling can actually profoundly increase the size and density of weeds if used on root spreading plants like Canada thistle and Leafy spurge because the individual root segments will grow into separate plants.  Tilling the soil can also invert the topsoil with sub soils, which may be of lesser quality soil.