Common hawkweed identification and control

Why it’s a problem

Common hawkweed is an aggressive competitor of pasture and range plant species. It is a serious pest of lowland pastures, mountain meadows, and lawns. Common hawkweed reproduces by seed and is mostly asexual, meaning a plant produces seed without fertilization. Therefore, it does not depend on pollination and can produce many seeds per plant, rapidly dominating an area.

They often invade sites in cleared forest zones which are low in available nutrients. Hawkweeds are thought to persist in these sites because they capture nitrogen in nutrient-poor soils, limiting nutrients available to competing plants. When hawkweeds form monocultures by establishing a dense mat of plants, they lower biodiversity and reduce the forage value of grasslands for grazing animals.

Plant description

General characteristics of hawkweeds

Hawkweeds were introduced to the United States from Europe as herbal remedies and ornamentals. Hawkweeds are all perennials (plants that have a 2+ year life cycle). They belong to the sunflower family and have a milky juice, yellow or orange dandelion‐like flower heads and bristly hairs overall. Plants have rosettes (a circular cluster of leaves on ground level). Basal leaves of most non‐native hawkweeds usually persist through flowering. Many non‐native hawkweeds have stolons (horizontal plant stems that root and form new plants), but not all, and there are no native Washington hawkweed species with stolons.

Hawkweeds can be found from sea level to high elevations and are most abundant at middle elevations in the mountains and along roadsides. Hawkweeds are perennials, can thrive in a wide range of conditions and are mostly found on roadsides and in fields, pastures, and mountain meadows.

Characteristics of common hawkweed

Common hawkweed has coarsely toothed leaves, no stolons, leafy stems, and open flower clusters.

Basal leaves are present and well‐developed at flowering time, but usually more gray‐green than smooth hawkweed. Also, basal leaves taper gradually to the petiole (leaf stalk). Stem leaves are similar to smooth hawkweed but usually only about 4 to 7 on stem.

Common hawkweed is different in that flower heads have abundant hairs and are fewer (4‐12) and plants are generally shorter, usually up to 16 inches tall.

Be aware of look-alike plants

There are many non-native and native hawkweed species in the pacific northwest, making individual hawkweed species very difficult to identify.

Many people think common hawkweed and dandelions look alike.

When in doubt, take photos and report them on iNaturalist.

What to do if you find it

Because common hawkweed is so widespread, property owners in King County are not required to control it. We are not generally tracking infestations. We can provide advice on how to control common hawkweed, but there is generally no legal requirement to do so.

The King County Noxious Weed Control Board encourages property owners to remove common hawkweed where possible, and to avoid introducing it to new landscapes.

Control methods

We recommend using a combination of methods to control weeds. In areas with few weeds, it is important to act quickly before they become harder to control. Make a long-term plan as it often takes several years to get rid of most weeds. Start in the least infested areas first and then move into more heavily infested areas.

For more in-depth control information, read Best Management Practices (BMP) for common hawkweed.

In areas where non-native hawkweeds are still limited in distribution, every effort should be made to contain and reduce the hawkweed before it is too established to control.

Mechanical control

Small populations can be removed by digging. Make sure to remove the entire root since plants can resprout from root crowns. If plants are in flower, bag and discard flowering stems to avoid spreading seeds.

Large areas infested with hawkweed are highly difficult to manage.

Mowing is not a recommended type of control for hawkweeds. Do not attempt to control by mowing unless mowers can be cleaned before moving to new areas and all the flowering stems can be collected and discarded. Plants will regrow after being mowed and flower again in the same season.

Chemical control

Stay safe when using herbicide: 

• Always read the label before use. 
• Wear a long-sleeved shirt, long pants, shoes, and eye protection. 
• Follow state and local regulations.

Herbicide may be useful for large infestations. If the site is wet or along the water's edge, it may require a permit issued by the state Department of Ecology. Use of a selective broadleaf herbicide such as triclopyr will be best to control non-native hawkweeds. Monitor the area for new plants that germinate from the seedbank for several years following initial treatment.

If you are qualified to do so or if your infestation is not near the water’s edge, follow these general best management practices:

Apply to plants in spring or early summer when plants are actively growing and before they fully flower. Flowering plants can go to seed immediately when sprayed.

Take care to avoid desirable plants. Contact your local noxious weed program or county extension office for recommendations on herbicides.

See the PNW Pest Management Handbook for the most up to date and specific methods for chemical control of common hawkweed.

Disposal instructions

Bag all flower heads. If the plants are in seed, carefully cut off the seed head and place in a bag without dispersing the seeds. Dispose of flower heads and plants in household garbage or take to a transfer station for disposal. Do not compost or put in yard waste. Never dump plant material in parks or natural areas because weeds can spread from yard waste piles.

Noxious Weed Disposal - Washington State Noxious Weed Control Board

Are your weeds piling up? - Noxious Weeds Blog