Weed Science

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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 identification of problem weeds you may encounter in your own fields, nursery or landscapes. More weeds profiles will be added as often as possible. Canada thistle flower

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.

Weed ID

Annual bluegrass Poa annua	In the Pacific Northwest, annual bluegrass usually germinates in late summer through spring when moisture is adequate.
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.
Bittercress Cardamine oligosperma	Bittercress is most problematic in propagation and overwintering of crops. It is most prolific from late fall through early spring.
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.
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.
Broadleaf Dock Rumex obtusifolius	Broadleaf dock, a perennial in the buckwheat family, has large, thick tap root.
Bull thistle Cirsium vulgare	Bull thistle is one of the most common thistles the Northwest. In fact, the specific name vulgare means 'common'.
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.
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.
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.
Creeping woodsorrel Oxalis corniculata	Creeping woodsorrel is one of the Oxalis species commonly found in Oregon nurseries and landscapes.
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.
Dandelion Taraxacum officinale	Dandelion is a hardy perennial which can be persistent in ornamental crops.
Field bindweed Convolvulus arvensis	Field bindweed is a deep-rooted perennial in the Morning-glory family.
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.
Horseweed Conyza canadensis	Horseweed is sometimes referred to as marestail. It is commonly a tall, erect summer annual weed.
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.
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.
Northern willowherb Epilobium ciliatum	Regionally, northern willowherb is known by several other common names, hairy willowherb, slender willowherb, or fringed willowherb.
Pearlwort Sagina procumbens	Pearlwort grows most aggressively in containers and gravel areas where water is abundant. It is commonly found growing with Liverworts.
Prostrate spurge Chamaesyce maculata	During Oregon’s typically cooler summers, Prostrate spurge usually becomes problematic only during the hottest part of summer.
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
Scarlet pimpernel Anagallis arvensis	Although it is not in the same family as the other chickweeds, scarlet pimpernel can also be called red chickweed.
Tansy ragwort Senecio jacobaea	Originally a native of Europe and western Asia, Tansy ragwort is an invasive weed in much of the Pacific Northwest.
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
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.
Yellow woodsorrel Oxalis stricta	Yellow wood sorrel is a species of Oxalis that is commonly found in nurseries and landscapes throughout Oregon.

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Weed Science

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PNW weed identification module

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