Galinsoga parviflora is an annual C3 herb (Pooter et al. 1990), germinates May-June, 20-60 cm tall, much branched, branches opposite, smooth to sparsely hairy.
Leaves opposite, stalk to 2.5 cm long, blade egg-shaped, to 2-5 cm long, 1-3 cm wide, tip pointed, base blunt, hairy on both sides, margins toothed.
Flowers white to pink, rays 5, 0.1-0.2 cm long, tip 3-toothed, no conspicuous basal scales (pappus), disk flowers yellow, 8-50, self-fertile, in heads 0.5 cm tall, 0.6 cm wide, 2-4 outer bracts with papery margins, persistent; blooms and fruits June-Nov. Blooms about 24 days after germination.
Fruit dry, 1-seeded achenes, blackish, ca 1 mm long, tipped with short, fringed scales; one plant producing up to an estimated 400, 000.
Wetland status: UPL.
Frequency in NYC: Infrequent.
Origin: SW US to S. America (USDA Forest Service 2006).
Habitat: Disturbed, open areas, vacant lots, an agricultural weed. Prefers damp, rich soil.
Notes: A reservoir for several mosaic and wilt viruses and nematodes of crop plants. Able to root from cut stems. Very sensitive to freezing. Hosts for numerous insects including Chrysomelid beetles, aphids, thrips, and Lepidopterans; also attacked by various nematodes and viruses (Warwick and Sweet 1983).