Artillery weed

Parietaria microphylla Linnaeus, Syst. Nat. ed. 10, 2: 1308. 1759

Herbs , annual or short-lived perennial, 0.3-2 dm. Stems 10-40-branched, erect. Leaf blades spatulate to obovate, paired blades unequal, the larger 3-10 × 1.5-5.5 mm, the smaller 1.5-4 × 0.7-2 mm, margins entire. Inflorescences crowded. Flowers ca. 0.5 mm across. Achenes uniformly light brown, slightly compressed, ovoid-cylindric, ca. 0.5(-1.1) × 0.3 mm, smooth.

Flowering all year. Waste places, hammocks, rocky woods, cultivated plots, on masonry; 0-100 m; Fla., Ga., La., S.C.; Mexico; West Indies; Central America; tropical South America; Pacific Islands (Hawaii); Asia.

Pilea microphylla has been collected once in Tennessee and once in Michigan, but it is unlikely that the species persists so far north. It is widely grown as a houseplant in the north and a border plant in the south. It is a greenhouse weed in various parts of the flora.