Time of bloom: July to September.
Seed-time: August to October.
Range: Ontario to the Dakotas, southward to Louisiana and Texas. Habitat: Prairies; meadows, pastures, and waste places.
A large, stout weed with square, pale green stems, often more than an inch in thickness at the base, four to eight feet tall, growing from thick, perennial roots in great tufts, or thickets. Leaves opposite, large, broadly oval, pointed, coarsely toothed, the upper ones united at their bases and forming rather deep cups which retain dew and rain. Lower leaves very large and abruptly narrowed to winged petioles, which are also joined at base; for their size the leaves are rather thin, and are of a sandpaper roughness on both sides. Flower-heads few because of the curious progression of bloom; the first one grows from the center of a cup, 2G while on each side of it springs a stalk, taller than itself, bearing a leaf-cup, which in turn will have a central head and two more cup-bearing stalks; these will fork again, and yet again, the series being sometimes "four stories high," as an observant child remarked. Each head resembles a small sunflower, two or three inches broad, with twenty to thirty narrow, yellow rays, pistillate and fertile; the disk-florets are sterile; involucral bracts in triple rows, broadly ovate, and conspicuous. Achenes encircle the outer edge of the head, as only the rays form fruit; they are oval, broad, brown, flat, notched at apex, winged on each side, with a pappus of two awn-like teeth. The same methods of extermination should be used as for the Compass Plant. (Fig. 313.)
Fig. 313. - Cup Plant (Silphium perfoliatum). X 1/8.