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Cocklebur (Xanthium strumarium)

• Family: Aster (Asteraceae)
• Flowering: August-October.
• Field Marks: The fruits are hairy in addition to having prickles all over them.
• Habitat: Fallow fields, along streams, in sloughs, wet prairies, disturbed soil.
• Habit: Coarse annual herb with fibrous roots.
• Stems: Erect, branched, usually hairy, up to 4 feet tall.
• Leaves: Alternate, simple, ovate, pointed at the tip, more or less heart-shaped at the base, shallowly lobed and toothed, hairy, up to 6 inches long, often nearly as broad.
• Flowers: Male and female flowers borne separately in small heads; each male head subtended by a series of small green bracts; each female head subtended by hooked prickles.
• Sepals: 0.
• Petals: 0.
• Stamens: 5.
• Pistils: Ovary inferior.
• Fruits: Achenes thick, embedded in a bur; the bur prickly, up to 1 inch long.
• Notes: Cockleburs contain a bitter poisonous substance that may cause death to grazing animals. The pollen may cause hay fever.