Lawn burweed (spurweed) (Soliva sessilis)
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Lawn burweed (spurweed) is a small, low growing winter annual broadleaf plant, often confused with pineappleweed or brassbuttons. In California lawn burweed occurs in the northwestern region, central-western region, southwestern region, Central Valley, Sierra Nevada foothills, and possibly other areas. However, its elevation limit has not yet been documented. Lawn burweed inhabits turf, compacted paths, roadsides, pastures, and disturbed, unmanaged areas. Its sharp, burlike fruit can puncture human and animal skin, making it a nuisance in turf.
Cotyledons (seed leaves) are oblong to narrowly oval and fused at the base. The first leaf pair is lance shaped, often with sparse hairs, and long tapered bases. Subsequent leaves are deeply and finely divided and covered with fine hairs.
Leaves are deeply and finely divided, covered with fine hairs, and are alternate to one another along the stem. Stems often branch at the base and usually have dark to purple spots. Although it may be confused with southern brassbuttons, lawn burweed leaves are shorter and usually palm shaped. It can be distinguished from pineappleweed by its hairy leaves and lack of conspicuous flower.
Flowers cluster into inconspicuous spiny flower heads and grow from where the leaf stalk meets the stem.
Each fruit is about 1/8 to 1/5 inches (3.5–5.5 mm) long, flattened, minutely hairy, winged, and has one spine. Two slightly curved teeth flank either side of the "spine".
One oval, flattened seed is found within each fruit.
Lawn burweed reproduces by seed.