COMMON RAGWEED, Ambrosia
artemisiifolia L. 1, plant; 2, seed; 3, distribution.
Annual, shallow-rooted. Stems rough, hairy, erect, branched,
1 to 4 feet (0.3 to 1.2 m) tall. Leaves nearly smooth, deeply cut
into a number of lobes, mostly alternate. Flowers of two kinds;
male pollen-producing flowers in small inverted clusters at tips of branches;
seed-producing flowers fewer, borne at the bases of leaves and in forks
of upper branches. Seed about 1/8 inch (3 mm) long, enclosed in woody hull,
light brown, top-shaped, pointed, bearing several longitudinal ridges ending
in short, spiny projections. Found in old pastures, wasteland, roadsides,
stubblefields, and cultivated land. Produces pollen abundantly and is a
hazard to hay fever sufferers.
LANCELEAF RAGWEED, Ambrosia bidentata
Michx. 4, portion of stem showing toothed leaves and flowers; 5,
seed; 6, distribution. Similar to the above. Leaves abundant,
lanceolate, partly clasping the stem, hairy, bearing 1, 2, or more large
sharp teeth on each side of a broad base. Seeds 4-angled with 4
sharp spines.
