Perennial pepperweed Lepidium latifolium Steve Dewey, Utah State University; Leslie J. Mehrhoff, University of Connecticut, Bugwood.org A 1 – 3 foot tall perennial with waxy leaves, white flowers, and creeping rhizomes. Also known as tall whitetop. Impacts riparian areas and wetlands by forming large dense stands that displace native plants.

Purple loosestrife Lythrum salicaria Linda Wilson, University of Idaho, Bugwood.org A 8 foot tall semi-aquatic perennial with long, showy, rose-purple flower spikes and square stems. Impacts wetland ecosystems by forming dense stands that displace native plants and impede water flow.

The Thistles Chris Evans, River to River CWMA, Bugwood.org Musk Cardus nutans Scotch Onopordium acanthum Steve Dewey, Utah State University, Bugwood.org Canada Cirsium arvense Mary Ellen (Mel) Harte,, Bugwood.orgForest & Kim Starr, United States Geological Survey, Bugwood.org Bull Cirsium vulgare

Scotch thistle A 4-8 foot tall annual with purple flower heads and spine tipped stems and leaves. Plants thrive in disturbed areas and can quickly become the dominant vegetation if left unmanaged. Onopordum acanthium Eric Coombs, Oregon Dept. of Agriculture

Canada thistle Steve Dewey, Utah State University; Theodore Webster, USDA Ag Research Service, Bugwood.org A foot tall perennial with small purple flowers and prickly leaves. Impacts a wide range of habitats including cropland and riparian areas. Creeping rhizomes can colonize an area feet in diameter in just a few years. Cirsium arvense

Field Bindweed Convolvulus arvensis A twining perennial with white, trumpet-shaped flowers. Impacts a wide variety of habitats including agriculture and home landscapes. Control is often difficult because plants reproduce vegetatively from roots, rhizomes, stem fragments, and by seeds that can lie dormant in the soil for up to 50 years.

Tribulus terrestris A yellow flowering annual that forms dense mats and hard, spiky seed cases that can injure livestock, people, and pets. Long-term control of puncturevine can be achieved by consistently reducing the amount of seed in the soil. Puncturevine

Garlic mustard Alliaria petiolata Leslie J. Mehrhoff, University of Connecticut, Bugwood.org A 3 foot tall biennial herb with self pollinating white flowers. All plant parts have a distinctive garlic odor when crushed. Impacts forested communities by altering the soil and out competing native plants.

Myrtle spurge Euphorbia myrsinites Patrick Nelson, Cottonwood Canyons Foundation An escaped ornamental containing a caustic sap that can result in skin irritation and swelling. Grows in a range of habitats from shaded oak under stories to sunny slopes.