This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Annual or biennial. Propagates by seeds.
Time of bloom: May to November.
Seed-time: July to December.
Range: Throughout North America except the extreme North.
Habitat: Fields, roadsides, and waste places.
Fig. 134. - Garlic Mustard (Allaria officinalis). X 1/3.
Common everywhere; a frequent tenant of vacant city lots; it is detested by the truck gardener because it harbors the club-root fungus so injurious to cabbage and turnips, and may have fouled the soil with the disease where those plants have never been cultivated.
Stems six inches to three feet tall, erect, slender, with branches spread rigidly at wide angles. Leaves deeply cut and lobed, with the lower segments usually turned backward. Flowers yellow, about an eighth of an inch broad, in small, flat clusters at summit of stem and branches, above lengthening rows of pods. These are small, round, slightly hairy, pointed, about a half-inch long, held erect and closely pressed to the stalk. When old both stems and pods often turn to a dirty purple, making the plant look still more weedy and unpleasant. (Fig. 135.)
Prevent seed production. Destroy autumn plants by hoe-cutting before fruiting stalks appear. Hand-pulling while in first bloom is a paying operation, as the plant is a gross feeder during the long season of seed development.