Welcome to the PNW weed identification module

Listed below are profiles of many commonly found weeds in nurseries and field production sites throughout the Pacific Northwest, including Oregon, Washington, Idaho, and Northern California. Use this data base to assist with the Canada thistle floweridentification of problem weeds you may encounter in your own fields, nursery or landscapes. More weeds profiles will be added as often as possible.

Each weed profile provides basic biological traits and cultural preferences for that weed, but for control and management options, we direct users to the Pacific Northwest Weed Management Handbook.

The easiest way to use this handbook is to look under the “Contents” tab on the drop-down menu across the top of the home page. Under this tab, the user can select from various crop type categories such as Christmas trees, Nursery, Greenhouse and Bulb crops, or Turfgrasses. Select the appropriate crop category, click and find valuable information for developing a working strategy for weed management.

Recommendations in this handbook are based on research results from the Agricultural Experiment Stations and Extension Services of Oregon, Idaho, and Washington. It is designed as a quick reference guide for weed control practices and herbicides used in various cropping systems and sites in our Pacific Northwest area.

The Pacific Northwest Weed Management Handbook is an invaluable resource, providing information and useful tools to assist growers and other industry professionals. Check out the tabs on Pesticide Safety, Tables and Calculations, as well as a Safety Checklist.

Annual bluegrass Poa annua In the Pacific Northwest, annual bluegrass usually germinates in late summer through spring when moisture is adequate. Image by: James Altland, USDA-ARS
Annual Sowthistle Sonchus oleraceae Annual sowthistle is a very common weed in northwest field nurseries. Because it can germinate quite rapidly, it can quickly become problematic in agricultural areas. Image by:James Altland, USDA-ARS
Bittercress Cardamine oligosperma Bittercress is most problematic in propagation and overwintering of crops. It is most prolific from late fall through early spring. Image by: James Altland, USDA-ARS
Bittersweet Nightshade Solanum dulcamara Bittersweet nightshade is a perennial vine that easily forms into a rambling shrub if not controlled. It is a native of Europe and is also known as woody nightshade or simply bitter nightshade. Image by: James Altland, USDA-ARS
Bristly Hawksbeard Crepis setosa Bristly hawksbeard is common weed in landscapes, lawns and unmanaged areas. It is easily confused, particularly in the rosette stage, with other members of the Asteraceae family. Image by:James Altland, USDA-ARS
Broadleaf Dock Rumex obtusifolius Broadleaf dock, a perennial in the buckwheat family, has large, thick tap root. Image by: James Altland, USDA-ARS
Bull thistle Cirsium vulgare Bull thistle is one of the most common thistles the Northwest. In fact, the specific name vulgare means 'common'. Image by: James Altland, USDA-ARS
Canada thistle Cirsium arvense Canada thistle is extremely difficult to kill. A single plant can develop a lateral root system with a 20 foot spread in a single season. James Altland, USDA-ARS
Common chickweed Stellaria media Common chickweed is primarily a winter annual broadleaf in the Pacific Northwest, but in some coastal areas, it can survive year-round. James Altland, USDA-ARS
Common groundsel Senecio vulgaris Although groundsel is a winter annual, it is very adaptable and often germinates and grows year round in Oregon's generally milder climate. Image by: James Altland, USDA-ARS
Creeping woodsorrel Oxalis corniculata Creeping woodsorrel is one of the Oxalis species commonly found in Oregon nurseries and landscapes. Image by: James Altland, USDA-ARS
Curly Dock Rumex crispus Curly dock is a perennial weed with a large, deep taproot.It originated in Europe and is found throughout the United States. Image by: James Altland, USDA-ARS
Dandelion Taraxacum officinale Dandelion is a hardy perennial which can be persistent in ornamental crops. James Altland, USDA-ARS
Field bindweed Convolvulus arvensis Field bindweed is a deep-rooted perennial in the Morning-glory family. James Altland, USDA-ARS
Field Horsetail Equisetum arvense Field horsetail is a perennial weed which is native to the Pacific Northwest. It is also one of the most difficult-to-control weeds in nursery crops. Image by:James Altland, USDA-ARS
Horseweed Conyza canadensis Horseweed is sometimes referred to as marestail. It is commonly a tall, erect summer annual weed. Image by: James Altland, USDA-ARS
Liverwort Marchantia polymorpha Liverworts are not vascular plants, but a more primitive life form similar to mosses. They do not have true leaves like most plants. Image by: James Altland, USDA-ARS
Mouseear chickweed Cerastium vulgatum As the name suggest, mouseear chickweed leaves are oblong, fleshy with pointed tips and prominent hairs or fuzziness-resembling mouse ears. James Altland, USDA-ARS
Northern willowherb Epilobium ciliatum Regionally, northern willowherb is known by several other common names, hairy willowherb, slender willowherb, or fringed willowherb. Image by: James Altland, USDA-ARS
Pearlwort Sagina procumbens Pearlwort grows most aggressively in containers and gravel areas where water is abundant. It is commonly found growing with Liverworts. Image by: James Altland, USDA-ARS
Prostrate spurge Chamaesyce maculata During Oregon’s typically cooler summers, Prostrate spurge usually becomes problematic only during the hottest part of summer. Image by: James Altland, USDA-ARS
Redroot pigweed Amaranthus retroflexus L. Redroot pigweed is a summer annual, but commonly germinates throughout the year with adequate moisture. When mature, it usually reaches a he Image by: James Altland, USDA-ARS
Scarlet pimpernel Anagallis arvensis Although it is not in the same family as the other chickweeds, scarlet pimpernel can also be called red chickweed. Image by: James Altland, USDA-ARS
Tansy ragwort Senecio jacobaea Originally a native of Europe and western Asia, Tansy ragwort is an invasive weed in much of the Pacific Northwest. Image by: James Altland, USDA-ARS
Wild carrot Daucus carota Because wild carrot is a biennial, it has a two year life cycle. The first year it forms a rosette of leaves, followed by a second year of f Image by: James Altland, USDA-ARS
Yellow nutsedge Cyperus esculentus Yellow nutsedge is a noxious weed and restrictions on shipping exist for many shipping destinations. It is a serious concern with field grown nursery stock, especially balled in burlap crops. Image: James Altland, USDA-ARS
Yellow woodsorrel Oxalis stricta Yellow wood sorrel is a species of Oxalis that is commonly found in nurseries and landscapes throughout Oregon. Image by: James Altland, USDA-ARS