This low-growing plant is difficult to identify because of its small size. It is more often located by the sharp burs that form after flowering. Lawnweed is mostly a problem in high traffic areas of turf where disturbance, compaction and short-mowed grass allows it to spread. Lawnweed can be controlled with good turf management practices such as fertilizing, regular watering, aerating and overseeding as needed.
Legal status in King County, Washington
Lawnweed (also known as carpet burweed) is a Class C noxious weed on the Washington State Noxious Weed List (external link). This species is also on the Washington quarantine list (known as the prohibited plants list) (external link) and it is prohibited to transport, buy, sell, offer for sale, or to distribute plants or plant parts, seeds in packets, blends or "wildflower mixes" of this species, into or within the state of Washington.
Additional information on lawnweed
What to do if you find this plant in King County, Washington
Because lawnweed is so widespread, property owners in King County are not required to control it and we are not tracking infestations. We can provide advice on how to control lawnweed, but there is no legal requirement to do so.
Lawnweed/carpet burweed photos - click for larger image