- Pest Type: Weed
- Crops Affected: Wheat, Cotton, Potatoes, Soybeans, Corn
- Scientific Name: Sida spinosa
- Pest Order: Malvaceae
Prickly sida is an erect, branched, summer annual broadleaf weed (20-60 cm tall). Spiny projections on the stem nodes account for the name.
Reproduction is by seed. Seeds may germinate over an extended period from spring through midsummer.
Cotyledons are rounded to heart-shaped (6-14 mm long by 5-8 mm wide), with a shallow indentation or notch at the apex. The hypocotyl and the margins of the leaves and cotyledons are densely covered with short, gland-tipped hairs.
Young leaves are alternate. Initial leaves are rounded to egg-shaped; subsequent leaves develop a pointed tip. Leaf blades are thin, soft, hairy, with prominent veins beneath. Petioles of young leaves are rounded, at least one-third as long as the blade, and bear short gland-tipped hairs. Stipules are present at the base of the third and all subsequent leaves.
Stems are much-branched and softly hairy, wit small spines at the leaf nodes. Hairs are branched (star-shaped). Leaves are alternate, softly hairy, 2-5 cm long, and oval or oblong to lanceolate. Margins are round - to sharp-toothed. Petioles are 1-3 cm long, with linear stipules (5-8 mm long) at the base.
Flowers are produced from June to September alone or in clusters of 2-12 mm flower stalks arising from the leaf axils. Flowers are pale yellow, with 5 petals, 4-6 mm long. Stamens are united over half their length to form a column. The fruit is a ring of five one-seeded segments, 1.8-3 mm long, with 2 sharp spines at the apex. The seed usually remains enclosed within the mericarp, but is flattened on 2 sides and rounded on the other (2-2.5 mm long).
Woody erect stems with spines in the axils may persist into winter.
A weed of most cultivated crops, prickly sida is also found in landscapes, fields, pastures, gardens, and waste places.
Prickly sida is found throughout the eastern United States extending north to MA and MI, and west to NE; but it is most common in the southeastern states.
Very young seedlings of prickly sida may resemble velvetleaf, but they lack the velvety foliar hairs. Foliage is also similar to Virginia copperleaf but can be distinguished by the coloration and spines at the stem nodes.