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Common Weeds to Watch for in Colorado & How to Control Them Full Guide of 2023

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common weeds to watch forStop and smell the roses – I know the saying is cliché, but truly, take a moment to appreciate the effortless beauty of nature all around you.

Yet peering closer, you may notice a few weeds creeping in, threatening to choke out the radiant blooms. Like any garden, our landscapes require attentive care. Let’s cultivate an awareness of common intruders, arming ourselves with knowledge to keep pesky weeds at bay.

Though the task may seem daunting, together we can nurture landscapes as vivid and fragrant as our imagination allows. Now breathe deep, roll up your sleeves, grab those gardening gloves – a little work today will allow our gardens to flourish.

The secret is taking it one patch at a time.

Key Takeaways

  • Know your area’s noxious weed lists and management priorities, such as eradication for List A weeds.
  • Certain widespread noxious weeds, like knotweeds and hybrid knapweed, require coordinated management plans to stop their spread.
  • Some persistent perennial weeds, such as nutsedge, may need complete tuber removal for control.
  • Some common lawn weeds, such as clover, can provide ecosystem benefits, so only spot treat or tolerate them.

Colorado Noxious Weed Lists

Colorado Noxious Weed Lists
As a gardener in Colorado, you need to be aware of the state’s noxious weed lists. List A species like Bohemian knotweed are designated for eradication, while List B species such as hybrid knapweed have management plans to stop their spread.

List C species are locally managed, and Watch List species including Japanese knotweed are monitored as potential threats. Although identifying and managing noxious weeds can be challenging, resources including County Weed Managers and CSU Extension are available to support your efforts.

List a Species

You’d be wise to watch for sneaky weeds such as henbit, chickweed, and bittercress as they begin sprouting up early every spring. Their fast expansion and durability can swiftly overwhelm your lawn if you don’t take measures.

Be prepared with some pre-emergence herbicide or other elimination tactics to stop them right away.

List B Species

You must take action to implement state management plans for hybrid knapweed and salt cedar to stop the spread of these List B noxious weeds across Colorado.

  • Survey and map distributions of the weeds.
  • Prioritize the most problematic areas for management.
  • Employ integrated strategies to control the weeds.
  • Consult local experts on best management practices.
  • Monitor efforts and reassess management plans annually.

This focused effort can help mitigate invasive weeds like knotweed and tamarix through science-based management plans.

List C Species

List C species like diffuse knapweed have state management plans to support local efforts, not stop spread, so you’d best learn to identify and manage such sneaky weeds in your own yard. Restricted noxious species require statewide management coordination. Contact extension specialists for herbicide advice to control the spread of knotweed and other weeds.

Pre-emergent and post-emergent herbicides, properly timed, can eliminate weeds before they thrive. Learn to spot Advisory Watch List species not yet known here. With knowledge and persistence, you can restrict troublesome weeds.

Watch List Species

Gotta keep an eye out for those tricky Watch List weeds before they become full-blown noxious invaders. Sneaky invaders like spotted and diffuse knapweeds, yellow and dalmatian toadflaxes, hoary cress, knotweeds, and tamarix threaten to elbow out native flora.

Although not yet noxious here, their proven menace elsewhere shows our gardens’ days could be numbered if we don’t take care. It is better to nip them in the bud with selective herbicides than watch our flowers displaced by these crafty weeds.

Identifying Unknown Weeds

Identifying Unknown Weeds
County Weed Managers and CSU Extension can both assist with positively identifying mystery plants, either through photos, plant samples, or descriptions. They can also recommend the most effective control methods tailored to your specific situation.

When an unrecognizable weed appears, don’t hesitate to contact these knowledgeable local experts, as proper identification is the critical first step toward successful and ecological weed management.

County Weed Managers

Contact your County Weed Manager and emotionally prepare to wage war against the insidious invaders threatening your lawn’s integrity. As a master gardener, I urge you to defend home lawns and maintain preferred plants.

Consider manual removal for light infestations, digging up weeds and roots entirely. For severe cases, apply natural boosters to strengthen turfgrass before problems arise. Reduce water usage and overseed thin areas to crowd out weeds. Hand-pulling perennials prevents reseeding of broadleaf and grassy weeds.

Partner with the county to identify risks early and determine integrated management plans, combining cultural, mechanical, biological, and chemical controls.

CSU Extension

You can also identify unknown weeds by contacting your local CSU Extension office. Their experts can help determine what’s growing in your yard and provide recommendations for management. Digging into weed lifecycles and cultural practices like proper mowing height and mulching benefits leads to natural solutions without chemical overuse.

Understanding the soil, grass type, and weed lifecycle enables targeting weeds when young through digging, mowing, or mulching instead of widespread herbicide application. Knowledge empowers you to manage weeds and nurture the yard’s health holistically.

Management of Noxious Weeds

Management of Noxious Weeds
You’ll want to stay on top of those pesky invaders in your lawn before they get out of hand. A bit of elbow grease or some clever concoctions applied at the right time can keep things tidy.

  1. Hand removal – For small infestations, manually dig up weeds. Use a forked weed tool to remove the entire root system.
  2. Mowing/cutting – Frequent mowing can help control some weeds and prevent flowering/seed production.
  3. Herbicides – Apply selective herbicides to target specific weeds without harming grass. Pre-emergents prevent germination, while post-emergents kill established weeds. Follow label directions carefully.

Repeated monitoring and quick action against tamarix chinensis, tamarix parviflora, tamarix ramosissima, giant knotweed, bohemian knotweed and other noxious weeds can stop invasion in its tracks. Consistent prevention practices like maintaining healthy pastures, monitoring for new growths, and utilizing integrated management techniques will keep these aggressive plants from gaining a foothold.

A vigilant gardener who uses multiple control methods at the optimal timing will reap lush, weed-free rewards all season long.

Three Major Noxious Weed Groups

Three Major Noxious Weed Groups
As a botanist or landscaper, you’ll want to keep a close eye out for these three major noxious weeds that can quickly overtake landscapes: Knotweeds, Hybrid Knapweed, and Salt Cedars. These aggressive spreaders have state management plans aimed at stopping their continued invasion across private and public lands through integrated approaches like education, research, and biological controls.


Knotty knotweeds, including Japanese, giant, and Bohemian varieties, are aggressive invaders that can take over your yard if you don’t act fast. These persistent perennials spread rapidly via rhizomes, forming dense thickets that crowd out native plants.

Employ an integrated strategy to control knotweed—repeatedly mow, dig, or spot treat young shoots with glyphosate. Monitor treated areas for regrowth and reapply as needed. Biological controls show promise to suppress knotweed long term.

Hybrid Knapweed

Hybrid knapweed combines tough characteristics like a mixed martial artist. This challenging hybrid weed crosses diffuse and spotted knapweed parents. Widespread in the Western states, its vigor and spread impact rangelands. Early detection allows management before extensive root establishment.

Hand pull small patches, being sure to remove all root fragments. For larger infestations, integrated management combines mowing and selected broadleaf herbicides. Consult local weed experts to learn identification and tailor plans to local conditions.

Success requires persistence, but together we gain ground against hybrid knapweed.

Salt Cedars

Tamarix chinensis, parviflora, and ramosissima are salt cedars included in List B with state management plans to stop their spread on private and public lands in Colorado. As an engaged gardener, understanding salt cedar impacts allows us to support meaningful management strategies.

Originally introduced from Eurasia, salt cedars aggressively invaded our western riparian habitats. Thoughtfully implemented control methods like biological agents can reduce spread while restoring diverse native communities.

Annual Bluegrass

Annual Bluegrass
You’re right, managing noxious weeds takes a coordinated effort. When it comes to annual bluegrass, you’ll want to watch for it starting its germination in late summer when soil temperatures dip below 70°F.

This tricky weed thrives in the cooler temps and is quite tolerant of shade. It’s a real bear to control because it doesn’t respond well to many common herbicides. You’ll need to determine the type of grass you’re dealing with before applying any chemical control, or you risk damaging the good grass.

Mowing higher can help reduce this weed’s competitiveness, but diligent pre-emergent herbicide application in early fall is key to preventing infestations. Hand weeding small patches can work when populations are low. But once established, you’ll be locked in an endless battle without using a multipronged approach.

When it comes to annual bluegrass, an ounce of prevention is truly worth a pound of cure.


As crabgrass invades, you’ll painfully watch your lush lawn transform into a patchy eyesore if you don’t act fast. This aggressive summer annual weed thrives in the heat, spreading rapidly by seed to form dense mats that crowd out turfgrass.

But with diligence and timely application of crabgrass preventer, you can halt this invasion in its tracks.

In spring, as soil temperatures rise above 55°F, carefully spot treat emerging crabgrass before it goes to seed using selective postemergent herbicides. Follow label directions closely to avoid potential damage to desirable grasses. For full season control, apply crabgrass preventer in early spring before the ground freezes to create a chemical barrier that prevents crabgrass seeds from ever establishing.

With patience and persistence, you can reclaim your lawn from this persistent warm-weather menace. Though frustrating, remember that crabgrass isn’t invincible. With a thoughtful plan and proper timing, your grass can prevail.


Goosegrass weeds will frustrate your weed control efforts this summer. Pre-emergent crabgrass herbicides are less effective on this pesky grassy annual. Watch for its light green color and dense mat of thinner, branched stems to set it apart from crabgrass.

Goosegrass germinates later in spring and summer than crabgrass. Time your pre-emergent herbicide split applications for both. Hand pull young plants after rain loosens the soil. For established patches, spot treat with post-emergent herbicides containing quinclorac, fenoxaprop, or MSMA.

Repeated herbicide applications and vigilant scouting will be necessary as goosegrass continues germinating into summer. But don’t lose heart! Consistent prevention and control will reward you with a goosegrass-free lawn next year.


Dig up that pesky nutsedge completely to finally be rid of its triangular stems poking through your lawn. As temperatures rise, that common nutsedge starts stretching skyward, its sparse growth creating bare patches in your turf where broadleaf weeds can encroach.

With a warm season growth advantage, nutsedge persists through summer’s heat long after cool season grasses wilt, emerging again in late summer.

But don’t just hack away stems and leaves – severing them actually stimulates nutsedge to generate new shoots. Only extracting the underground tubers can conquer this sedge. So take that garden fork in hand, feel for the nut-like tubers congregating a few inches down, then lift them fully out.

Shake off clinging soil, gather tubers in bags for disposal, and breathe easy knowing nutsedge won’t sprout again from remnants left behind.

Enjoy a rejuvenated lawn, thick and lush, freed from those triangular invaders.


Dandelion, plant of the daisy family Asteraceae, has long been scorned as a weed but also valued as an edible green and herbal medicine. Though herbicides temporarily banish its bright yellow blooms, resilience is this flower’s virtue.

Dandelion’s sunny faces belie its tenacious roots. Unsightly in lawns, every remnant of root left behind sprouts anew. Manual removal by digging may work for small infestations but proves laborious. Broad-leaf herbicides kill existing dandelions but not the seeds lurking underground.

Repeated applications must target young plants to prevent them maturing. Still, it’s an endless battle where nature usually wins.

Rather than fight, make peace: let dandelions flourish in part of the yard. Enjoy their early spring blooms, so vital for bees. Harvest the tangy greens for salad. Make sweet dandelion wine from the brilliant flowers.

Weeds or wildflowers: it’s all in how you look at it. With a shift of perspective, dandelions show their sunny side.


You’d want that clover even though it spreads rapidly, for it provides nitrogen and bee food. While clover may overtake patches of lawn, consider the benefits it brings. This hardy perennial fixes nitrogen in the soil, enriching the lawn with a natural nutrient source.

The nectar-rich clover flowers attract bees and other pollinators, supporting biodiversity. As it spreads via rhizomes, clover forms dense mats that choke out other weeds. Though you could eliminate clover completely with a three-way herbicide, try a more balanced approach.

Set your mower higher to allow clover’s low growth habit to blend into the turf. Spot treat only larger infestations, rather than blanketing the entire yard. Tolerate clover’s presence in lower traffic areas.

With thoughtful management, clover can enhance your landscape’s health and beauty.

Frequently Asked Questions (FAQs)

What are the best herbicides to use for controlling common lawn weeds?

When tackling common lawn weeds, start by identifying the offenders. Doing so allows you to select targeted pre- and post-emergent herbicides. Spot treat persistent perennials such as dandelion and clover. For widespread annuals like crabgrass, apply pre-emergents in early spring.

Combination products offer efficient control of diverse weed populations. With patience and diligence, you will be rewarded with a lush, weed-free lawn.

How often should I apply weed control products for the best results?

You, dear gardener, should wisely apply weed control products frequently for fabulous results. Applying treatments twice per year prevents abundant problems and promotes proper plantings. However, beware of overapplying, as moderation maintains landscape magnificence.

What time of year is it best to treat lawn weeds?

You’ll get the best weed control by treating in early spring before weeds emerge and again in fall to target new growth. Carefully identify weeds first, then choose selective herbicides that target the weeds but won’t harm your lawn grass.

How long does it take for weed killers to work on my lawn?

The timing depends on the weed and product used, but most post-emergent killers take 7-14 days to fully wither broadleaf or grassy invaders. Pre-emergents work more slowly, stopping seeds from sprouting over 2-3 months. Patience pays off for a pristine lawn, pal.

Are there any natural or organic weed control methods I can try before using chemical herbicides?

Try spot spraying vinegar or boiling water for annual weeds. Pulling by hand works on young weeds before roots establish. For perennials, repeated digging may weaken them over time. Solarization using plastic sheets can also help.


My friend, the way lies open before you. These weeds may seem a burden, but they are teachers. Heed their lessons, and care for your garden with patience and wisdom. The path winds, yet with each step we draw nearer the bright meadows ahead.

Keep watch, wield your tools judiciously, and the common weeds will trouble you no more.

Avatar for Mutasim Sweileh

Mutasim Sweileh

Mutasim is a published author and software engineer and agriculture expert from the US. To date, he has helped thousands of people make their yards lush and thick.