Lawnweed
Soliva sessilis
Washington State Classification
Class C — Widespread, County-Selected Control
It produces very sharp seeds (burs) that can puncture skin and attach themselves to tires.
Quick Reference
Identification
Growth Habit
Lawnweed is a low growing winter annual. The plant will grow to about two inches tall, with a spread of six inches in diameter.
Leaves
Plants have basal leaves (cluster of leaves at base of stem) and alternately arranged stem leaves. Leaves are 0.4 to 0.8 inches and are pinnately lobed, giving them a feathery appearance.
Flowers
Small flowerheads occur in leaf axils from February to July. Flowerheads are made up of greenish-translucent disk flowers and lack ray flowers.
Fruit & Seeds
The flat, hard seeds (achenes) are small, light-weight, and tipped with serrated spines, essentially forming a bur, that makes dispersal by human activities common.
Impact
It produces very sharp seeds (burs) that can puncture skin and attach themselves to tires. It can out-compete perennial grasses of managed lawn areas. It dies back in the summer leaving open, bare areas, which contribute to its spread. Lawnweed was changed from a Class B to a Class C noxious weed in 2013.
Ecology & Spread
Habitat
It is found in managed perennial grass areas usually associated with heavy foot traffic, public swim areas, and boat launches of public lakes, watered lawns, golf courses, and hard-packed soils near paths and roadsides. Please click here to see a county level distribution map of lawnweed in Washington.
Spread Mechanisms
Reproduction
It is a winter annual and reproduces from seed. Germination begins early and seedlings develop rapidly, resulting in dense local cover and eliminating competition from neighboring vegetation.
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Control Methods
Mechanical
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Biological Control
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