Erect or ascending annual herb, 3–60 cm high, often branched at base. Leaves 2(–3)-pinnate, lamina 1–7.5(–30) cm long; leaflets ovate, ultimate segments narrow-linear, hispid on veins and margins; petiole of basal leaves as long or longer than lamina, slender with a narrow sheathing base. Umbels irregular, almost sessile or with 2–5 unequal rays to 5 cm long; umbellules 1–6-flowered, c. 1.5 mm diam.; involucral bracts 1–3, linear to narrow-lanceolate, often with membranous margins, often hispid, usually pinnatifid; involucral bracteoles narrow, entire. Petals minute, often purplish. Fruit ovoid, 3–6 mm long, primary ribs with a row of short bristles that spread alternately on each side of the rib, secondary ribs with hooked bristles Flowers Sep.–Feb.