This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Biennial. Propagates by seeds.
Time of bloom: July to October.
Seed-time: The earlier flowers mature in September, but fruits remain on the stalks all winter if not disseminated nor destroyed.
Range: Eastern Canada and New England, southward to Pennsylvania and Ohio: locally in Middle Western States.
Habitat: Fence rows, roadsides, and waste places.
The presence of one of these huge weeds in flower and fruit should be considered a disgrace to the owner of the soil so occupied, for it must have remained in undisturbed possession of the ground for the necessary second year of growth before reproduction.
The root is enormous; often three inches thick, driving straight downward for a foot or more and then branching in all directions, taking strong hold on the soil and grossly robbing it. Stem four to nine feet in height, stout, ridged, rough-hairy, with spreading branches. Leaves broadly oval, the lower ones often more than a foot in length and nearly as wide, rather thin but strongly ribbed and veined, with wavy or slightly ruffled edges which save them from being torn by the wind, light green, woolly and felt-like beneath but darker and smooth above, with deeply furrowed, solid petioles dilated at base to clasp the stem. Heads in crowded axillary clusters, each sometimes more than an inch broad, often on rather long peduncles; florets all tubular and perfect; corollas pink, five-lobed, the ring of anthers purple, stigmas and pollen white; bracts of the involucre in many series, rigid, hooked inwardly at the tip, spreading at differing angles, making the heads nearly globular. Achenes oblong, three-angled, mottled gray and brown, crowned with a short, bristly pappus. Widely distributed in the burs by animals, and on garments of passers-by. (Fig. 353.)
Burdock roots and seeds are used in medicine and the destruction of the weeds may sometimes be made profitable; roots should be collected in autumn of the first year of growth, cleaned, sliced lengthwise, and carefully dried; the price is three to eight cents a pound; ripe seeds bring five to ten cents a pound.
Fig. 353.- Great Burdock (Arctium Lappa). X 1/8.
Destroy the seedlings by hoe-cutting; some will escape and spread sprawling rosettes, which must be deeply cut with spud or hoe; if merely shaved at the top, the food-filled root will immediately crown itself anew, but deep cutting kills. If any are left until the second year, cut the flowering stalks close to the ground before any of the heads are mature.