Invasive Weeds in Wyoming: How to Identify and Stop Them Before They Take Over

Invasive weeds are one of the most persistent and costly problems facing Wyoming property owners, ranchers, and land managers. A 2024 University of Wyoming study found that just 10 invasive weed species are causing economic damage that could exceed $110 million across the state — and cheatgrass alone is leading the charge. Knowing which plants to watch for, and what to do when you find them, is the fastest way to protect your property.

If you are trying to remove invasive weeds from your Wyoming property, contact us today to see how we can help.

What’s the Difference Between an Invasive Weed and a Noxious Weed?

The terms are related but not identical, and the distinction matters.

An invasive weed is any non-native plant that spreads aggressively and disrupts the local ecosystem — crowding out native plants, altering soil chemistry, reducing biodiversity, or diminishing the land’s value for wildlife and agriculture. An invasive plant becomes a noxious weed when the state of Wyoming or a county weed and pest district formally designates it as legally regulated. In other words, all noxious weeds are invasive, but not every invasive plant has yet made the official list.

If you want to understand the legal side of noxious weed management in Wyoming, our post on noxious weeds and Wyoming property owner requirements covers that in detail. This post focuses on the practical side: what these plants look like and how to stop them.

Which Invasive Weeds Should Wyoming Property Owners Know?

Cheatgrass (Downy Brome)

Cheatgrass is Wyoming’s most economically damaging invasive plant according to the University of Wyoming’s 2024 report, with potential economic impacts that may exceed $110 million statewide. It looks like ordinary grass early in the season — fine, soft, and green — but by midsummer it turns red-brown and dry. That’s when it becomes dangerous. Cheatgrass dries out weeks earlier than native grasses, dramatically increasing wildfire risk across Wyoming’s rangelands and open spaces. It also recovers faster after fire than native plants, creating a cycle that slowly converts diverse native plant communities into cheatgrass monocultures.

On residential and commercial properties, cheatgrass establishes in thin or disturbed turf, gravel areas, fence lines, and slopes. It’s one of the first things to green up in Wyoming’s spring and one of the first to go to seed — often before homeowners realize it’s there.

Field Bindweed

Field bindweed is a gardener’s nightmare throughout Wyoming. It has small heart-shaped leaves and delicate pink or white trumpet-shaped flowers that look almost pretty — which is part of why it gets ignored until it’s a serious problem. Underground, bindweed spreads through a deep, extensive rhizome system that can reach 10 feet or more into the soil. Pulling it only stimulates regrowth. It wraps around and smothers desirable plants, is extremely drought-tolerant, and thrives in Wyoming’s dry conditions.

Once established in a garden bed, bindweed requires a consistent, multi-year management approach to suppress. It won’t go away on its own.

Myrtle Spurge

Myrtle spurge is one of the most important plants to identify because it is sometimes sold as an ornamental at nurseries, despite being invasive throughout Wyoming and much of the western United States. It’s a low-growing succulent with blue-green leaves and yellow-green flowers that appears attractive in rock gardens and dry slopes — which is exactly how it ends up on residential properties.

The problem: myrtle spurge spreads aggressively through seed, is toxic to people and animals (the milky sap causes skin irritation and eye damage), and is nearly impossible to remove once established without protective gear and persistent effort. If you have it in your yard, it needs to come out — carefully, and with gloves.

Spotted Knapweed

Spotted knapweed is widespread across Wyoming’s roadsides, pastures, and disturbed areas. It produces thistle-like purple flowers and spreads rapidly through seed — a single plant can produce over 1,000 seeds per year. What makes knapweed particularly damaging is that its roots release chemicals into the soil that suppress the growth of surrounding native plants, a process called allelopathy. Over time, a knapweed infestation converts biodiverse native areas into dense single-species stands.

Hoary Cress (Whitetop)

Hoary cress, also called whitetop for its clusters of small white flowers, is an aggressive perennial that outcompetes native plants and significantly alters soil nutrient balance. It spreads through both seed and underground root fragments, meaning any soil disturbance — a shovel, a tilling pass, a grading project — can inadvertently spread it. It’s particularly common in Wyoming’s irrigated areas, roadsides, and disturbed soils, and early detection is essential because established populations are very difficult to eradicate.

Common Tansy

Common tansy is a tall, upright plant with bright yellow button-like flowers that can be visually striking — another invasive that gets planted intentionally before its behavior is understood. It spreads by both seed and underground rhizomes, forms large colonies in moist areas, and is toxic to livestock. Along Wyoming’s creek corridors and irrigation ditches, tansy can establish quickly and is difficult to control once it gets a foothold.

Why Does Wyoming Have Such a Serious Invasive Weed Problem?

Wyoming’s landscape makes invasive weed management uniquely challenging in ways that homeowners moving from other states often underestimate.

Disturbed soils are everywhere. Wyoming’s boom-and-bust development cycles, road construction, agricultural operations, and regular landscaping and grading work constantly create the bare, disturbed soil that invasive weeds colonize first. Any time soil is opened up in Wyoming — whether for a new driveway, a planting bed, or a construction project — it becomes an open invitation.

Snowmelt and runoff move seeds at scale. Each spring, Wyoming’s heavy snowpack releases and flows across the landscape, carrying weed seeds from roadsides, neighboring properties, and public lands into previously clean areas. Creeks, ditches, and drainage paths become seed highways.

Wind. Wyoming’s persistent wind carries lightweight seeds — thistle, knapweed, cheatgrass — extraordinary distances. A healthy-looking property in July can have new weed pressure established from seeds that arrived in May.

Wildlife. Elk, deer, bison, and pronghorn move across Wyoming’s landscape daily and carry invasive weed seeds on their fur and through their digestive systems. Properties near wildlife corridors and public lands face constant reintroduction pressure regardless of how well they manage their own ground.

Short growing season. Wyoming’s cold climate gives desirable plants a narrow window to compete. Many invasive species are more cold-hardy than the native plants they’re displacing, germinating earlier in spring and establishing faster under conditions that slow down everything else.

How Do You Remove Invasive Weeds From Your Property?

The right approach depends on the species, the size of the infestation, and your property’s proximity to waterways or sensitive habitat.

For small, early-stage infestations: Hand-pulling can be effective for some species — but timing and technique matter. Pulling too late (after seed set) can spread the problem. For plants like myrtle spurge, wear gloves and protective clothing every time. Bag and dispose of pulled plants — don’t compost them.

For established perennial species like bindweed, knapweed, and cheatgrass: mechanical removal alone is rarely enough. These plants regenerate from root fragments or quickly recolonize from seed. Targeted herbicide applications timed to the plant’s active growth stages produce significantly better results. For properties near Wyoming’s streams and waterways, product selection and application methods require extra care to meet state water quality requirements.

Prevention is the cheapest strategy of all. Monitoring your property regularly — particularly any areas with disturbed soil, new plantings, or recent construction — and catching invasive plants in their first season is dramatically less expensive than managing an established colony. Choosing native plants for new landscaping projects also removes one of the most common ways invasive species arrive on residential properties in the first place.

If you’re planting new beds or redesigning outdoor spaces and want guidance on plant selection that won’t create future problems, TLC’s gardening services are built around exactly that kind of thoughtful, Wyoming-appropriate planting. And for ongoing management of existing weed pressure, our weed control programs provide a consistent, season-to-season approach that keeps infestations from compounding year over year.

The Best Time to Act Is Before the Weeds Get Ahead of You

In Wyoming’s short growing season, the gap between “manageable” and “established infestation” can close in a single season. The best strategy is a proactive one — getting ahead of invasive plants in early spring before they flower and set seed, rather than reacting to a problem that’s already spread.

Pre-emergent herbicide applied at the right time is one of the most effective tools for annual invasive species like cheatgrass. We break down how that works and when to time applications in our guide to pre-emergent weed control for lawns.

. For perennial invasives, consistent multi-year management is the realistic expectation — but with the right plan in place, even serious infestations can be brought under control.

Contact TLC Today

Frequently Asked Questions About Invasive Weeds in Wyoming