Noxious Weed Alert and Quick Reference
Weed Alert is an introduction to identifying common weeds around Spokane County and the simple methods of how to control and eradicate them. It will provide residents, farmers and ranchers of the Spokane area with the links and resources to effectively fight noxious weeds. Email notifications will keep subscribers aware of current stages of weeds and the best method of managing them. Sign up at right to stay in the know with Weed Alert!
Weed species have been around a long time and are excellent survivors, removing them requires patience and continued efforts. The best strategy to remove weeds is to take an integrated approach that uses multiple methods of eradication. Before attempting to remove weed species, a plan should be made for what the land will be used for; otherwise, opening the land to new species after removing noxious weeds will result in stronger and a larger abundance of weeds to thrive in their place. Our small acreage custom operation can help you design and implement a plan if do it yourself is not feasible.
Common Noxious Weed Overview
Name: Spotted Knapweed (Centaurea stoebe)
Introduction: From Eurasia as a contaminant of alfalfa and clover seed
Habitat: Any disturbed soil
Infestation: Vacant lots, pastures, rangeland, roadsides, stream banks and landscaping
Available Control: Mechanical, chemical, and biological
Priority of Control: Preventing plant from going to seed, attack in rosette stage
Biological Controls: For more information about these biological control agents of Spotted Knapweed, please visit WSU Extension Integrated Weed Control Project.
For More Detail: Visit the Washington Noxious Weed Control Board listing for Spotted Knapweed.
Name: Canada Thistle (Cirsium arvense)
Introduction: Native to southeastern Eurasia, contaminated crop seed
Habitat: Rich, heavy loam, clay loam, and sandy loam, with an optimum soil depth of 20 inches
Infestation: Crops, pasture, rangeland, roadsides, stream banks and landscaping. It can crowd out forage grasses by up to 60 percent. It can also invade native plant communities.
Available Control: Mechanical, chemical, biological
Priority of Control: Deplete its root reserves before rosette has a chance to over-winter.
Biological controls: For more information about the biological control of Canada Thistle, please visit WSU Extension Integrated Weed Control Project.
For More Detail: Visit the Washington Noxious Weed Control Board listing for Canada Thistle.
Name: Common Bugloss (Anchusa officinalis)
Introduction: From Eurasia as a contaminant of alfalfa and clover seed
Habitat: Common Bugloss was originally found growing near Mead, WA. It has spread throughout most of north Spokane County with limited distribution in the south portions of the county.
Infestation: Pastures and rangelands and is a concern to alfalfa production because the succulent leaves and stalks mold the hay once it is baled.
Available control: Chemical, and mechanical
Priority of Control: The most effective control of Common Bugloss is prevention. Above all, prevent plants from going to seed.
Biological Control: There is no known effective biological control for Common Bugloss
For More Detail: Visit the Washington Noxious Weed Control Board listing for Common Bugloss.
Introduction: Native of southeastern Europe and introduced as an ornamental plant because of its snapdragon-like flowers.
Habitat: Coarse, well-drained soils
Infestation: Roadsides and rangelands, in fields, overgrazed pastures, idle cropland and waste areas.
Available control: Mechanical, Chemical, Biological
Priority of Control: Prevent from flowering, keeping foliage down without spreading root fragments
Biological Control: For more information about the biological control of Dalmatian Toadflax, please visit WSU Extension Integrated Weed Control Project.
For More Detail: Visit the Washington Noxious Weed Control Board listing for Dalmatian Toadflax.
Name: Rush Skeletonweed (Chondrilla juncea)
Introduction: Central Asia and the Mediterranean Basin including North Africa, Morocco, Turkey, Italy, Spain and Portugal.
Habitat: Well-drained, sandy-textured or rocky soils.
Infestation: Rangelands, semi-arid pastures, croplands, transportation right-of-ways, residential properties and other areas subjected to repeated soil disturbance.
Available control: Mechanical, chemical, and biological.
Priority of Control: Prevent root fragments from producing new plants, prevent from seeding
Biological Control: For more information about the biological control of Rush Skeletonweed, please visit WSU Extension Integrated Weed Control Project.
For More Detail: Visit the Washington Noxious Weed Control Board listing for Rush Skeletonweed.
Introduction: European plant in either contaminated lawn seed or hay
Habitat: Adapted to dry soils and can out compete other plants.
Infestation: Waste places, overgrazed pastures, and stressed meadows.
Available control: Mechanical and chemical
Priority of Control: Prevent plant from getting to flower.
Biological Control: There are no insects for biological control of hoary alyssum available at this time.
For More Detail: Visit the Washington Noxious Weed Control Board listing for Hoary Alyssum.
You can also contact Spokane County Noxious Weed Control Board:
509-477-5777 or visit www.spokanecounty.org/weedboard
Rosette Stage Information: What to do in Early Spring
Rosette: Rosette is the beginning stage of weed development. Root development, storing energy, and the greatest level of vulnerability occur at this stage. Because they begin early spring, a plan should be made to use multiple methods for eradication. Act fast because weeds grow quickly, and get harder to remove the longer they have to establish.
Description: Rosette is hairy and rough with a somewhat wooly appearance with deeply lobed leaves radiating from a common point.
Timing: March- May, August-October
Rosettes are formed the first year and appear in early spring and later fall
Mechanical: For small areas, hand pulling can be effective. After taproot is established or large areas, chemical methods are most effective for eradication.
Caution: Chemicals found in Knapweed fibers are possibly carcinogenic, wear thick gloves before pulling
Chemical: 2,4-D, WeedMaster, Range Star, Rifle D, Brazen, or Milestone. Please use the Spokane County Weed Board Herbicide Guide.
Description: Leaf color ranges from light to dark green. Sharp spines are numerous on the outer edges of leaves, branches and main stem of the plant. Leaves are spine-tipped and wavy, growing alternately and slightly attached to the stem.
Timing: May- June
Mechanical: Handpulling small infestations, removing all root. (Wear gloves)
Chemical: WeedMaster, Range Star, Rifle D, Curtail, Milestone, or Brazen. Please use the Spokane County Weed Board Herbicide Guide.
Description: It forms a thick rosette of basal leaves in its first year. Leaves get furry with time, making chemical application very difficult later in the season.
Mechanical: Large, woody taproots make Common Bugloss very difficult to remove manually. Small infestations can be dug out with a pick or shovel, removing as much of the root as possible.
Chemical: For optimal control, spray with a broadleaf herbicide when the weed is still in the rosette stage. 2, 4-D, Brazen, or Telar. Please use the Spokane County Weed Board Herbicide Guide.
Description: The light-green, waxy leaves are heart-shaped and clasp the stem. Reproduces both by creeping root stocks and by seed. The horizontal roots produce many buds that form new colonies.
Time: March- May
Mechanical: Successful hand pulling or digging can be done on very small infestations, being sure to dig out the roots. Larger patches can be controlled by clean cultivation. Repeat as needed so that there are never more than 7—10 days of visible green growth. It could take up to 2 years to eradicate.
Chemical: Can be used but may miss some stocks that could come up later in the season
2, 4-D, WeedMaster, Range Star, Rifle D, Telar. Please use the Spokane County Weed Board Herbicide Guide.
Description: Rosettes that resemble dandelions.
Time: Begins in the fall with seed germination and growth of perennial root, over winters as rosettes, initiates growth by mid- April
Mechanical: For very small infestations, diligent hand pulling or grubbing two or three times a year, for six to 10 years, can be helpful. New plants will emerge from severed roots and buried seeds. Pull out the young weed when the soil is wet.
Chemical: In the spring, spray when the plant is still a rosette, or at least no later than when it is about to bolt.
- Spray the new rosette later in the fall, after the first frost.
- Spraying rosettes twice a season, early in the spring and later in the fall, should eradicate the weed after three years.
• Milestone and 2,4-D have been very effective in Lincoln County. Please use the Spokane County Weed Board Herbicide Guide.
Description: Leaves are alternate, oblong, gray-green and covered with rough hairs. Forms deep taproot.
Mechanical: Hand pulling, and digging up the tap root can help control the spread.
Chemical: 2,4-D, WeedMaster, Prescott, or Opensight. Please use the Spokane County Weed Board Herbicide Guide.
Caution: Plant produces a toxin, when injested by horses can result in pregnacy complications. When 30-70% of feed contains Hoary Alyssum, animal death may result.
Bolt Stage: What to do in Early Summer
Bolt Stage: The bolting stage is when the shoot of the plant rises out of the rosette in order to produce a multitude of flowers. Managing weeds in this stage may not be as effective as the rosette stage but it will still be more effective than when the plant goes to flower.
Description: Spotted Knapweed produces several branched, upright stems growing from a stout taproot and usually grows up to 3 feet tall.
Mechanical: Mowing should be done more than once a season with different mower levels because Spotted Knapweed will adjust to the height of the mower. Keep in mind, mowing does not eradicate the plant but rather only removes the seed heads, requiring seasonal and annual maintenance to prevent the spread.
Chemical: Transline, Milestone, or Roundup (spot spray only). Please use the Spokane County Weed Board Herbicide Guide.
Description: Shoots emerge from rosette reaching 1 to 4 feet tall that branch into clusters of lavender to deep rose-purple flowers that are urn-shaped and bractless.
Mechanical: Mowing stimulates new thistle shoots to develop. It is a good idea to combine mowing or cultivation with chemical control. After tillage or mowing, allow the thistle to reach 6-8 inches, spray with an herbicide and resume tillage or mowing 10-14 days after spraying.
Chemical: Spray when plant is actively growing and majority of leaves have emerged, but prior to bud stage. For spot treatments during the bud stage, use roundup. As the thistles grow past the bud stage, control will decrease, but fall applications can be made if there is adequate moisture and regrowth. Telar, Milestone, or Roundup (spot spray in bud Stage). Please use the Spokane County Weed Board Herbicide Guide.
Description: The shoots are robust and hairy and grow 1 – 2 feet tall at maturity. The lower leaves are lance shaped. The slightly pointed leaves are succulent and fleshy and covered with thick stiff hairs.
Timing: June- July
Mechanical: Small infestations can be dug out with a pick or shovel, removing as much of the root as possible.
Chemical: As the plant grows, you will need to use a higher rate of herbicide. Because the hairs on the leaves make it difficult for herbicides to penetrate the plant, you will need to add a surfactant such as R-11, Activator 90, or Syltac, to increase coverage with herbicides 2, 4-D or Brazen. Please use the Spokane County Weed Board Herbicide Guide.
Description: It is an attractive plant (resembles snapdragon) with a shoot that can grow up to 3 feet tall.
Timing: June – July
Chemical: Studies show that the best time to spray toadflax is at the beginning of the flowering stage (usually in May). Be sure to add a surfactant (R-11 or Activator 90 or Syltac) to the spray mix to increase coverage and penetration of the waxy leaf surface. Fall applications may prove effective, if only to reduce the number of plants that return in the spring. Telar, WeedMaster, Range Star, or Rifle D. Please use the Spokane County Weed Board Herbicide Guide.
Description: Multiple prickly stems arise from rosette
Mechanical: hand pulling (wear gloves) and sealing bags can prevent seeds from spreading, will not eradicate plant
Chemical: Milestone and 2,4-D have been very effective in Lincoln County. These products can be used to the edge of a creek. Any later than bolt stage, spray can be ineffective. Please use the Spokane County Weed Board Herbicide Guide.
Description: Stems are gray-green, hairy, and typically grow from one to three feet tall with many branches near the top.
Mechanical: Mowing, hand pulling and digging. Remove deep tap root.
Chemical: WeedMaster, Brazen, or Opensight. These products can be used to the edge of a creek. Any later than bolt stage, spray can be ineffective. Please use the Spokane County Weed Board Herbicide Guide.
Flower Stage: Summer through Fall
Flower: When attempting to eradicate noxious weeds, best efforts are performed prior to the flowering stage. However, preventing the spread of weed seeds and creating a management plan for the following year is essential to success. If weeds have reached seed, don’t get discouraged; rather, prepare both the land and yourself to remove fall re-growth and get ready for spring arrivals.
Description: Flowers are pink to purple and surrounded by stiff, black-tipped bracts, giving the flower head a spotted appearance. Flowering stalks elongate the second year. It flowers continuously from early summer into the fall. Most seeds can remain viable in the soil for 7 to 10 years. In order to effectively manage Spotted knapweed, it is best to prevent the plant from reaching seed.
Mechanical: Mowing down the flowered plant or old growth will prevent the seeds from spreading to other areas by forcing them onto the ground. Removing the old growth will allow better access in the spring to the rosettes and because the seeds were forced down, a plan can be made to spray and work on the single area and over managing the spread.
Chemical: Spraying dry seed heads or late season plants neither sterilize nor kills them. If new growth is present or fall rosettes form use 2,4-D, WeedMaster, Range Star, Rifle D, Brazen, or Milestone. Please use the Spokane County Weed Board Herbicide Guide.
Fall Regrowth: See Spotted Knapweed Rosette section.
Description: Lavender to deep rose-purple flowers that are urn-shaped and bractless. Male and female flowers are found on different plants and both must be present to produce.
Timing: July- August
Mechanical: Remove flowers and keep in sealed containers. Remember; try to exhaust the root energy from creating more shoots.
Chemical: Try to prevent plant from ever reaching bud or flower stage. Best managing practice is to attack plant in rosette and bolting stage.
Fall Regrowth: See Canada Thistle Rosette
Caution: Canada Thistle infests crops, pasture, rangeland, roadsides, stream banks and landscaping. It can spread quickly to form dense colonies, crowding out forage grasses by up to 60 percent. Most grazing animals avoid Canada Thistle infested areas due to spiny leaves that can lead to mouth irritations and infections.
Description: Each flower stem starts out coiled like a fiddleneck, then straightens out as each flower bud opens. The flowers are initially reddish, later turning to a deep blue to purple flower with white centers. Each flower produces 4 small, nutlet-like seeds. One plant can produce an average of 900 seeds, which can remain viable in the soil for several years.
Mechanical: Remove all of root and plant and seal flowers from spreading seeds
Chemical: Visit the Spokane County Weed Board for more information on chemical prevention of Common Bugloss.
Fall Regrowth: See Common Bugloss Rosette
Caution: Common Bugloss invades pastures and rangelands and is a concern to alfalfa production because the succulent leaves and stalks mold the hay once it is baled. It is important to remember that it will take a continuous effort to control Common Bugloss, regardless of what control method is used. Regrowth may occur in the same growing season and followup is key. If rosettes are found in the fall, spraying or cutting can help reduce spring populations.
Description: Flowers are bright yellow with long spurs and orange-bearded throat that resembles a snapdragon. A mature plant can produce up to 500,000 seeds per year. The seeds can remain dormant in the soil for up to 10 years.
Timing: August- October
Mechanical: Handpulling or cultivation every 10 days for 2 years. Mowing to ground level during flowering will reduce seed production but does not provide control of the creeping root stocks.
Chemical: There is no chemical treatment for a flowered seed head
Fall Regrowth: See Dalmatian Toadflax Rosette
Caution: The waxy leaf, deep root system and heavy seed production make this a difficult plant to control. Irregular tilling may spread infestations since small root pieces can pro-duce new shoots. Mowing to ground level during flowering will reduce seed production but does not provide control of the creeping root stocks.
Description: Seeds develop nine to 15 days after yellow flowers open. A plant can produce up to 20,000 seeds and 90 percent are capable of germinating. Seeds may remain viable for up to four years.
Mechanical: Hand pulling and sealing bags help keep seeds from dispersing.
Fall Regrowth: See Rush Skeletonweed biological controls and chemical controls for rosettes.
Caution: Do not till or cultivate patches of Rush Skeletonweed since root fragments will develop into new plants and spread the infestation. Rush Skeletonweed reduced wheat yields by as much as 80 percent, The weed can foul up harvesting machinery and contaminate the wheat crop. This weed will also reduce crop yields on farmland by aggressively out-competing for nutrients and soil moisture.
Description: Flowers are white with four deeply divided petals. Seeds are found in oblong hairy pods with a short beak at the end. Plant continuously flowers and seeds throughout the summer and late fall.
Mechanical: Mowing down the flowered plant will prevent the seeds from spreading to other areas. Dig or pull out the taproot and put seeding and flowering plant in area where it cannot spread.
Fall Regrowth: If there is fall regrowth due to mowing: WeedMaster or Opensight
Caution: Toxic to horses. Can cause complications in pregnancy and even death if too much is found in feed (>30%).
Biological Controls are insects used as part of an integrated weed management strategy. Because insects need the weeds to survive themselves, they will not eradicate plants but rather establish equilibrium where they both live in the same time and place. Their function is to reduce spreading weed populations. This process may be very long and take multiple years, but it can naturally reduce weed populations. Eradication will require long term chemical and mechanical integration as well.
To request availability of biological control agents through UDSA including:
- Cyphocleonus achates
- Larinus minutus
- Mecinus janthinusformis
To buy local Biological Controls for 16 different noxious weeds:
Contact: Gary Piper
Click to view printable flier about biological control of noxious weeds.
- The knapweed root weevil (Cyphocleonus achates) larvae feed within spotted knapweed roots. Available mid-July – September
- Seedhead weevil, Larinus minutus, larvae destroy spotted knapweed seed in the seedheads. Available mid-May – July
- Click here for more information about these biological control agents of spotted knapweed.
- Fly larvae of the stem gall fly Urophora cardui impact plant vigor in Canada thistle. Growth and flowering can be retarded, but this agent alone does not kill plants or prevent spread. Available June
- Larinus planus, Seed eating beetle. Available May-June
- For more information about the biological control of Canada thistle, please visit WSU Extension Integrated Weed Control Project.
Common Bugloss Biological Control: There is no known effective biological control for Common Bugloss
- The toadflax stem weevil, Mecinus janthinus is a very effective biocontrol agent used in Washington state to control Dalmatian toadflax. Available mid-May – June
- For more information about the biological control of Dalmatian toadflax, please visit WSU Extension Integrated Weed Control Project.
- A gall mite (Eriophyes chondrillae) was introduced to Washington in 1979, and it is considered the most effective biological control agent available to date. This mite is effective against all biotypes of Rush Skeletonweed. The visible impacts to flowering buds are leaf-like galls, up to 2 in diameter, which can reduce or prevent seed production.
Hoary Alyssum: There are no insects for biological control of hoary alyssum.
It is important to control noxious weeds to help protect our diverse native plants, natural resources, and agriculture. Although some noxious weeds may serve as forage for bees and other pollinators, the detrimental impacts of these invasive plants significantly outweigh their value as a pollen and nectar source. One of the best things you can do is replace noxious weeds with quality non-invasive forage plants that bees and other pollinators need to stay healthy. Check out this resource on plant materials.
You can do your part to control destructive noxious weeds and still be the bee’s knees.
- Replace noxious weeds with non-invasive, pollinator friendly plants
- Use plants that bloom from spring through fall to provide bees and other pollinators with food throughout their active season.
There are many resources available about noxious weed control and bee-friendly gardening, including your
- Local County Noxious Weed Control Board,
- WSU Extension office
- County Conservation District
Timing is important. Make sure to time your noxious weed control so that it minimizes disturbance to the bees.
- Do your control work in the morning or in the evening when bees are less active.
- Control as many noxious weeds as you can in early spring, fall, or even winter when plants are not in bloom.
- Plant desirable species in conjunction with the weed control so the bees still have a source of nectar and pollen.