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: June to September. Seed-time: August to December.
Range: Throughout North America except the far North. Habitat: All soils; meadows, pastures, roadsides, and waste places.
This plant is said to be the progenitor of the cultivated carrot, but its long, tapering root has none of the succulent sweetness which careful selection and cultivation has given to its descendants; on the contrary, it is filled with woody fibers, acrid to taste and said to be poisonous. Only a crown of green leaves is produced the first season; these are twice or thrice pinnate, the segments lance-shaped and toothed, giving the plant a fine, feathery appearance; petioles long, slender, swollen at base, grooved on the upper side; the leaves are rough-hairy, have an unpleasant odor when bruised, and their acrid juices protect them from grazing animals. Flower-stalks appear the second year, one to three feet tall, erect, slender, branching, bristly with stiff hairs, bearing few, sessile, and clasping leaves; flowers clustered, in large, flat, compound umbels, white, except that there is usually one in the center of each umbel which is dark purple; rays of the umbel crowded, the inner ones shorter than the outer rows, all subtended by a whorl of green, finely cut, involucral bracts. As the fruits mature the outer rows of pedicels bend inward, making the umbel concave and forming the "bird's nest." Carpels thickly set with weak spines along the secondary ribs, forming a small, oblong, gray-brown bur which is light in weight and may be carried far by the wind or drifted with snow; these seeds have long vitality and one seeding may pester the soil for several years. The plant is frequently infested by the leaf-spot fungus, Cercospora apii, which is very injurious to Celery. (Fig. 214.)
Hoe-cutting or spudding the leaf-crowns from the roots during the first season, and closely cutting, or, better, hand-pulling, the flowering stalks of the second year. In grain fields the latter method is the only way to fight the weed effectively, for it is resistant to sprays that would not also destroy the accompanying crop. In cultivated ground the plant gives little trouble, for there it may be uprooted with hoe or cultivator in its first season - a process which at once destroys it.