How does our HOA comply with Colorado noxious weed law on our open space?

By OurHOA · General information · Revised October 29, 2026

What Colorado's Noxious Weed Act asks of an HOA board: List A, B and C weeds, county notices and the 10-day reply, penalties, licensed crews and a yearly plan.

Part of the HOA board handbook: vendors, projects and upkeep.

The short answer

Find out which noxious weeds grow on your common area, learn what your county requires for each one, and put a written plan and a licensed crew on it before the county weed inspector shows up. Under C.R.S. 35-5.5-104, every person who owns or controls land has a duty to manage noxious weeds that are likely to materially damage neighboring land, and the statute's definition of "person" includes associations. An HOA that owns open space, detention ponds, greenbelts or entry medians is a landowner with that duty. This guide covers Colorado. Texas, Florida and other states run their own weed and invasive plant programs, and your declaration may assign some areas to the association and others to owners. Treat this as education, not legal advice, and call your county weed manager early. They are usually glad to help a board that asks before a complaint comes in.

What the lists mean for your land

Colorado's Department of Agriculture (CDA) sorts state noxious weeds into three lists under C.R.S. 35-5.5-108, and the list decides how much the board has to do. List A plants are rare in Colorado and must be eradicated wherever they are found. The current list includes myrtle spurge, cypress spurge, purple loosestrife, yellow flag iris, orange hawkweed and the Japanese, giant and Bohemian knotweeds. If one of these is on your open space, eradication is mandatory, not a goal. List B plants are established in parts of the state. The commissioner sets an objective for each species county by county: eradication, containment or suppression. Canada thistle, musk thistle, diffuse and spotted knapweed, Dalmatian and yellow toadflax, leafy spurge, Russian olive, salt cedar and oxeye daisy are all List B. CDA posts each county's List B plan, so look up yours rather than guessing. List C plants, such as field bindweed, cheatgrass, puncturevine, common mullein, Siberian elm and tree of heaven, are widespread. The state recommends control but does not require it. Your county or city can. Two more rules matter. Section 108(2)(b) lets a county or city adopt stricter standards than the state, and 108(3) lets it add local noxious weeds after a public hearing with 30 days' notice. And section 104.5 makes it unlawful to introduce, cultivate or sell a designated noxious weed, or to knowingly allow one to grow in violation of the act. A state noxious weed that is being properly managed under CDA rules is not a violation.

When the county sends a notice

C.R.S. 35-5.5-109 sets out the process, and the clock is short. Inspection. The county or city can inspect when the owner asks, when a neighbor reports a suspected infestation, or when an inspector sees one from a public road or area. It must notify the landowner by certified mail first. If the association refuses entry, the inspector can get a court warrant. Notice. If weeds are found, the notice names them and the control methods the county expects. The 10-day reply. Within a reasonable time, never more than ten days after receiving the notice, the landowner must do one of three things: comply, acknowledge the notice and submit an acceptable plan with a schedule, or ask for an arbitration panel. For most boards the middle option is the right one, because a crew rarely finishes a large open space in ten days. If the association does nothing, the county can do the work and bill the full cost plus up to 20 percent for inspection and incidental costs as a lien on the parcel. That lien ranks ahead of all others except general taxes and prior special assessments. Counties can also prosecute a violation as a civil infraction under section 118.5, which HB 26-1239 rewrote effective August 12, 2026. A court must impose $100 to $2,650 per violation, with presumptive maximums of $500 for a first, $1,000 for a second and $2,650 for a third or later one. Each day of violation counts as a separate offense. CDA can add its own civil penalty of up to $1,000 per violation under section 118.

Write a plan for the open space

A plan is what turns the 10-day notice from a scramble into a phone call. Keep it to two or three pages. 1. Map it. Walk every tract in late spring and again in midsummer with a printed site plan. Mark each patch, the species and a rough size. CDA uses the free EDDMapS system and accepts reports from private landowners, so a volunteer with a phone can log locations and photos. 2. Confirm the species. Send photos of anything you are unsure of to the county weed manager or CSU Extension office. Misidentifying a List A plant as a common weed is the expensive mistake. 3. Set the objective for each species from the state list and the county's List B plan: eradicate, contain or suppress. 4. Pick integrated methods. The act defines these as biological, chemical, cultural (favoring desirable plants through seeding, fertility and moisture) and mechanical (mowing, pulling, mulching, grazing). Use more than one. 5. Budget for years, not one season. Put a weed line in the operating budget and revisit it each fall. Keep the map, plan, contractor reports and county letters in the association records. If an inspector calls, the board can send the plan the same day.

Timing for the weeds boards see most

Canada thistle is the List B plant most Front Range HOAs fight. CSU Extension's fact sheet says its horizontal roots can run 15 feet or more and that root pieces a quarter inch long can grow new plants, so pulling and tilling spread it. Mowing alone only works at about one-month intervals over several growing seasons. Herbicides work in spring before flower buds form, and CSU notes fall treatment gives the most consistent results for several products. Retreatment in one to four years is normal, so tell owners up front this is a multiyear job. Myrtle spurge is a List A plant that came into Colorado as a garden ornamental. Jefferson County warns the sap can burn or irritate skin and that mowing is not recommended because it spreads seed. Crews and volunteers who dig it need gloves, long sleeves and long pants. For knapweeds and toadflax, the timing and products vary by species. Ask your contractor to follow the current CSU herbicide recommendations that CDA links from its weed list page, and to note in each report which plants were treated, where and when.

Hiring a weed crew

Anyone who applies herbicide on association land for hire is a commercial applicator under C.R.S. 35-10-103, and the work is pesticide work even when it is a landscaper with a backpack sprayer. Section 35-10-106 requires a licensed commercial applicator business to carry at least $400,000 in liability insurance and to have a qualified supervisor licensed in the category of work. Before the first visit, collect the CDA business license, the supervisor's license and a certificate of insurance naming the association. Put these items in the scope of work, and our guide on hiring an HOA landscaping contractor covers the rest of the contract: - The weed map and the objective for each species. - Number of visits and the months for each. - A written report after each visit with species, location, method and product. - How the crew will protect ponds, trees and pets, and post treated areas. - Reseeding of bare spots, since bare ground invites the next infestation. - A named contact who will meet the county inspector if asked.

Owner lots and landscape rules

Weeds do not stop at the lot line, and section 104 applies to owners too. The board's job is to keep its own rules from making the problem worse and to tell owners what the law already says. Check the approved plant list in your design guidelines. Remove anything on the state list. Myrtle spurge, oxeye daisy, dame's rocket and Russian olive all are, and all have been planted in yards. Then send owners a short notice. Wording you can copy: "Colorado law requires every landowner, including the association and each homeowner, to manage state noxious weeds. Some, like myrtle spurge, were once sold as garden plants and must now be removed. The board is treating weeds on the open space this season. If you find a plant on your lot you can't identify, send a photo to [contact] or the county weed program. Please wear gloves when pulling spurge; the sap irritates skin." A motion for the minutes: "I move that the board adopt the attached noxious weed management plan for Tracts A through D, approve a contract with [company] at a cost not to exceed $[amount], and direct the secretary to keep the plan and contractor reports with the association records."

A sample year and the usual mistakes

January: set the budget and send owners the plant notice. April and May: survey and map, confirm species, first treatment of rosettes. June and July: dig or treat List A plants before seed set, mow thistle patches monthly where mowing is the method. August: second survey. September and October: fall herbicide treatment on perennials, reseed bare spots. November: update the map and plan, and file the year's reports. Mistakes boards make: letting a lawn crew without an applicator license spray; mowing myrtle spurge or seeding knapweed and spreading it; ignoring a certified letter until the ten days are gone; treating once and calling it done; and leaving bare ground behind. If the open space also has burrowing animals, our guide on managing prairie dogs on HOA open space in Colorado covers barriers and permits that fit into the same yearly walk-through.

Sources

These guides are general education for HOA boards and residents, not legal, tax, or financial advice. Rules vary by state and by your community's governing documents - check with a professional for your situation.

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