Hieracium pilosella • Class B

The plant has a basal rosette of narrow, pointed leaves, with a single, upright yellow flower head that resembles a dandelion. The leaf tops are covered in bristly hairs while the undersides have a soft wooly feel. Plants contain a milky juice. The flowering stalks are covered in short bristly hairs and are usually leafless, but occasionally have 1 or 2 small leaves and stand about 3 to 10 inches tall. Its seeds are purplish black, short, columnar with many white bristles (pappus) on one end of the seed which act like a parachute as the wind distributes the seed. 

It is not allelopathic, but its creeping growth fills in the gaps between other plants forming mats of rosettes which prevents other plants from establishing seedlings. 

Mouse ear hawkweed infests forests, pastures, meadows, wetlands and suburban lawns and is especially invasive on infertile, shallow or coarse soils in regions of relatively high rainfall. It does not tolerate shade. 

This noxious weed out competes pasture and native plants. As desirable forage plants are replaced by the somewhat unpalatable hawkweed, biodiversity decreases. 

Early detection and eradication are important to prevent the spread of hawkweed. Prevent new infestations by maintaining good ground cover with perennial grasses and clover. 

• Treatment with nitrogen will help the grasses to competitively suppress hawkweed growth for up to 3 years. 

• Pulling, digging up, mowing, etc. is ineffectual in controlling this noxious weed. 

• There are no known biological control agents. 

• Spot spraying with an herbicide containing the active ingredient glyphosate (Roundup Pro, Glyfos, etc.) may be used effectively in the spring while the plant is in the pre-bud to early bud growth stage. The goal is to insure all plants have emerged. Spray each plant thoroughly on the stems and leaves, enough to be wet but not dripping. Be aware, glyphosate is non-selective and will injure any plants that it comes in contact with, including grass. 

• For selective control of hawkweed in agricultural settings (pastures, hayfields, etc.): an herbicide containing the active ingredient aminopyralid (example: Milestone, Milestone VM, etc.) may be applied in the spring to plants in the pre-bud to early bud growth stage. It is also effective in the fall before a killing frost. Amino-pyralid products will not harm grass and can be used around livestock (provided all label precautions are followed). 

• When using herbicides, read and follow all label instructions and obey all label precautions. (Note: pesticide product registration is renewed annually and product names and formulations may vary from year to year.) 

 Download our Flyer or visit Washington State Noxious Weed Control Board Here. Photo by Leo Michels