Origin:
Native to the Mediterranean area and southern Europe. Now scattered over much of the U.S.
Biology:
An annual weed, extremely prostrate and mat-forming, spreading out in a circle to 10 feet in diameter. Very shallow but tough taproot. Seeds germinate in early spring, but can remain viable in the soil for 5 years. Plants mature throughout the summer, and may produce copious amounts of seeds. Seeds are spiked and very hard, creating havoc with bicycle tires that easily are punctured.
Identification:
Stems are long, thin, and trailing along the soil, up to 5 feet long. Leaves form on opposite sides of the main stem, are hairy, and are divided into 4 to 8 pairs of leaflets. Flowers are yellow, less than ½ inch wide, and borne in the axils of the leaves. Fruits, or seedpods, are composed of 5 sections, that break apart into thorny, tack-like structures at maturity. Each section has 2 long, sharp, slightly curved spines and 2 to 4 seeds inside.
Characteristicts Important to Control:
The spiny seeds are commonly carried in vehicle tires, spreading the weed quickly. Seeds may remain viable in soil for 5 years, increasing difficulty of control. The seeds tangle in sheep wool, making it damaging, they are a problem in hay, and may injure livestock that consume them. Weeds grow in most soil conditions, from cultivated fields to hard packed roadsides, trails and paths as well as gardens. Individual plants may be physically removed prior to production of the seeds. Seeds may remain viable in the soil for several years before they germinate.
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