Ambrosia L. >

Burrs without hooked appendages, each burr containing 1 fruit (Fig. 41) Ambrosia
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Fruiting head without spines but with teeth, hairy. Perennials
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Leaves 2–4-pinnate, linear to oblong, mostly up to 10 cm long. Perennial herb with long suckering roots. Widespread. Weed of roadsides and waste places. Introd. from America. Fl. spring–summer Ambrosia tenuifolia