Spanish Needles (Bidens bipinnata)
This is one of those flowers that reward a close look. The flowers are like tiny marigolds, and indeed they’re sometimes called bur-marigolds. The seeds, long and narrow like marigold seeds, have hooks that stick in animal fur or people’s clothes. These grew at the edge of a yard in Beechview.
From Gray’s Manual of Botany: B. bipinnata L. (SPANISH NEEDLES.) Smooth annual, branched; leaves 1-3-pinnately parted, petioled; leaflets ovate-lanceolate, mostly wedge-shaped at the base; heads small, on slender peduncles; outer involucre of linear bracts equaling the short pale yellow rays; achenes 4-grooved, nearly smooth, 3-4-awned, very unequal. Damp soil, R. I., westw. and southw.; occasional on ballast northw.