370 



WEED FLORA OF IOWA 



Burdock (Arctium lappa L.). 



Description. — A coarse, branched biennial 1-3 ft. high; hairy; 

 leaves large, roundish or heart-shaped, thin, obtuse, entire or den- 

 tate, floccose, tomentose beneath; petioles deeply furrowed, heads 

 of purplish or whitish flowers, clustered or somewhat corymbose; 

 involucre surrounding ■ the flowers lengthened into hooked tips, 

 glabrous or slightly cottony; trichomes simple, long, twisted. 



Distribution. — Burdock has long been known as a troublesome 

 weed in the northern states and in Europe. Quite common from 

 New Brunswick to Alabama and the Rocky mountains, the Great 

 Basin country and on to the Pacific coast. Common in grain 

 fields and waste places in many parts of the state. 



Fio. 217. Burdock (,ArcUum lappa). Common in waste places. A biennial 



weed ; "seeds" scattered by animals. 



(Photographed by Gardner.) 



