Carpet burweed (Soliva sessilis) is an invasive broadleaf winter annual that threatens open areas in parks, golf courses and RV parks. It forms a ‘carpet’ in the turf, spreads easily and is difficult to identify.
Carpet burweed is a low-growing plant, measuring up to 3-5 cm in diameter and 7 cm tall. The alternate, carrot-like leaves are slightly hairy with a greenish flower head growing in the basal rosette of the leaves. The ovate, flattened achenes can be slightly hairy, with a thick spine. The horn-like seed measures 2.5-3.5 mm long with 5-10 seeds per seedhead. It is commonly mistaken for Parsley-piert, Queen Anne’s lace, Pineapple weed, Dovesfoot geranium and Spring gold.
Seed spread occurs when the seed spine punctures the skin of humans and animals or attaches to animal fur/paws, footwear, clothing, maintenance or recreational equipment (i.e. tents, tarps, mowers, etc.), lawn clippings and vehicle/bike tires.
Carpet burweed can be found in isolated areas on the Southern Gulf Islands and Vancouver Island, as far north as Ucluelet. Once discovered, the plant is rapidly eradicated to prevent further spread.
It can out-compete tended grasses and is unaffected by mowing due to its low-lying structure. Depending on the site, carpet burweed can be removed by hand pulling, burning or herbicide application. For other identification and control options, see the link below.