Public Works | Utah County

Detection Guidelines

Utah County is home to a variety of noxious weeds that threaten native ecosystems, agriculture, and recreational areas. Early detection is essential for effective management and prevention of their spread. This page provides guidance on identifying the most common noxious weeds found in our region.

What are noxious weeds?

Noxious weeds are invasive, non-native plants designated by the State of Utah as harmful to public health, agriculture, and the environment. These species spread aggressively, outcompeting native plants and disrupting natural habitats

How to Identify Noxious Weeds

For identifying noxious weeds in Utah County, use the Utah State University Extension's Noxious Weed Field Guide and the Utah Weed Control Association's updated guide, both of which provide detailed images and identification features for each species. Online resources, including county-specific PDFs and field guides, offer photos, height ranges, leaf and flower structures, and maps to help compare suspected plants. Suspected noxious weeds can be reported via the EDDMapS app by submitting photos and location data for expert verification. Always refer to current state or county lists for accurate identification, as species and names can change over time

REPORT NOXIOUS WEEDS

Noxious Weeds in Utah County

Canada Thistle

Cirsium arvense

Forms dense colonies, crowding out native species and reducing habitat for wildlife and beneficial plants.

Dyer's Woad

Isatis tinctoria

Produces chemicals that inhibit other plants, overtakes rangelands, and decreases native biodiversity.

Hoary Cress

Lepidium draba

Infestations can outcompete native flora and are mildly toxic to livestock, diminishing both crop and natural habitats.

Squarrose Knapweed

Centaurea virgata

Spread creates monocultures by suppressing neighboring plants, threatening grazing land and diminishing biodiversity.

Russian Knapweed

Rhaponticum repens

Toxic to horses and extremely persistent, it replaces native vegetation and makes habitat restoration nearly impossible.

Yellow Starthistle

Centaurea solstitialis

Dense, spiny infestations destroy forage areas and are highly poisonous to certain animals, especially horses

Diffuse Knapweed

Centaurea diffusa

Produces toxic chemicals and dominate landscapes, reducing space for livestock, wildlife, and agriculture.

Scotch Thistle

Onopordum acanthium

Thick growth creates barriers, restricting access and competing with native flora for space and nutrients

Musk Thistle

Carduus nutans

Prolific seed production quickly overwhelms native habitats and decreases valuable wildlife and forage areas.

Phragmites

Phragmites australis

Thick stands displace native wetland plants, increase fire risk, and degrade aquatic and terrestrial habitats.

Poison Hemlock

Conium maculatum

Every part contains potent toxins, causing severe illness or death for humans and animals upon even small exposures.

Purple Loosestrife

Lythrum salicaria

Large colonies choke out other wetland vegetation, drastically reducing food and shelter for native wildlife.

Cutleaf Vipergrass

Scorzonera laciniata

Its rapid spread can dominate grasslands and disturbed areas, threatening the health of native ecosystems and wildlife.

Garlic Mustard

Alliaria petiolata

Fast-spreading undergrowth disrupts entire forest communities by releasing chemicals that inhibit growth.

Giant Reed

Arundo donax

Rapidly overgrows waterways and riverbanks, increasing fire and flood risk and destroying habitat for native species.

Oxeye Daisy

Leucanthemum vulgare

Prolific seeds enable takeover of pastures and wild areas, leading to long-term ecosystem imbalance.

Reporting

If you find a plant you suspect to be a noxious weed:

Take clear photos of the plant, focusing on leaves, flowers, and growth habits.
Note the location and estimated size of the infestation.
Report findings to the Utah County Weed Control Program or use the EDDMapS app for verification and mapping

For a complete list of noxious weeds and detailed identification guides, refer to the Utah State Noxious Weed List and the Noxious Weed Field Guide for Utah. Early detection and accurate identification are vital to protecting Utah County's landscapes from invasive weeds. Visit our resources page for more information on reporting and next steps.