This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Native. Annual or biennial. Propagates by seeds.
Time of bloom: May to October.
Seed-time: June to November.
Range: Illinois to Montana, southward to Mexico, Texas, and
Florida. Widely distributed in tropical America. Habitat: Dry, sandy soil; fields, waste places.
The milky juice of this plant, like that of all its tribe, will irritate and blister the skin, and, if eaten by stock, will have a like effect on the inner membranes and make the animals very sick; another reason for its name of Cruel Plant is that honey gathered from its flowers is acrid and emetic and unfit for use.
Stems one to three feet tall, erect, smooth or nearly so, bright green, woody at base, with numerous branches, the lower spreading, the upper ones ascending. Leaves alternate and all with slender petioles, but most variable in shape, some being round, or ovate, or lance-shaped, or linear, with edges entire or toothed or wavy, often on the same plant; sometimes the upper leaves are fiddleshaped, and to add to their oddity are blotched with deep red. The involucres are in terminal clusters, each on a peduncle of about its own length, with five much incised, ovate lobes, bearing usually one, occasionally several, cup-shaped glands, which are sessile or nearly so, and without appendages. Seeds nearly globular, roughened with small tubercles.
If not too numerous, the plants are best destroyed by hand-pulling as soon as observed; or by cutting so closely and frequently that no seed will be allowed to mature.
 
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