Propagates by seeds. Time of bloom: July to October. Seed-time: August to November.
Range: Massachusetts to Georgia and Tennessee, westward to the Missouri River; also in Idaho, Oregon, and Washington. Most abundant in the Ohio Valley and in the states bordering on the Great Lakes. Habitat: AU soils; invades all crops.
A noxious weed that owes its wide range almost entirely to the agency of impure seed. It first appeared in Massachusetts not many years ago, and has since journeyed from ocean to ocean and could probably be found now in every state in the Union. In addition to its robbery of the crop in grain fields, the hard stems dull the reaping knives, and the copious, milky juice makes the weed very troublesome in threshing machines when handling a crop immediately after the reaping, without drying in the shock, as is frequently done in the West.
Stem erect, with short lateral branches, round, smooth except for a few prickles near the base, sometimes attaining a height of seven feet but usually two to five feet tall; occasionally it has a purplish tinge. Leaves alternate, light green, oblong, variable, often obtuse at tips but sometimes acute, with wavy, prickly-toothed edges and thick, whitish green midrib, closely set with spines on the under side, sessile, clasping, auricled at base. Leaves of plants growing in the open have a vertical twist at the base which causes their edges to point north and south; plants growing in the shade have not this twist to the leaves. Heads numerous, in a large panicle at the summit of the stalk and on short axillary branches; pale yellow, each less than a half-inch broad, on very short pedicels; beginning at the top, they open a few at a time, daily. Achenes brown, ridged lengthwise, with thread-like beak and pappus of fine, white, silken hair. (Fig. 374.)
Fig. 374. - Prickly Lettuce (Lactuca scariola, var. integrata). X 1/6.
Fig. 375. - True Prickly Lettuce (Lactuca scariola).
Not quite so obnoxious nor so common as the variety just described, but still a very bad weed, is the True Prickly Lettuce (L. scariola, L.) differing chiefly in that its prickly ribbed leaves are lobed or pinnatifid, and the smooth or sparsely prickled woody stalk usually taller; the heads are similar but slightly smaller, very numerous. The plant ranges from New England and Pennsylvania westward to Michigan and Missouri. (Fig. 375.)
Deep cutting of the tufted root-leaves, well below the crown, with hoe or spud; cutting of flowering stalks at the beginning of bloom or earlier. In a grain field, hand-pulling of the young flower-stalks before bloom will be a paying operation, as the crop will not be worth much if the weed is allowed to absorb the fertility and moisture of the soil. Rankly infested ground should be put under cultivation for the purpose of stirring dormant seed into life and destroying the seedlings. Sheep and young cattle graze the young plants freely and prove good assistants in keeping the weed in check, but milch cows must not have much of it as the juices are bitter and will taint the milk. Seeds are widely wind-sown, and it is to the interest of the entire community to see that none are allowed to mature in roadsides and waste places.