Spanish Needles (Bidens bipinnata) — identification, habitat & look-alikes

Spanish needles is an annual in the aster family, best known for its slender, barbed seeds that cling to socks and clothing. It grows across much of the central and eastern United States, often in disturbed ground and along woodland edges.

Appearance

Appearance: An upright annual usually 2–5 ft (0.6–1.5 m) tall, with green or reddish, angled stems that are nearly hairless.
Leaves: Opposite leaves are divided two or three times into small, fern-like segments.
Flowers: Small heads of golden-yellow sit on long stalks at the stem tips. Each head has up to five tiny yellow , and some heads have none.
Flowering time: Late summer to early fall.
Fruit: The seeds are long, narrow, four-sided, and dark brown, with 2–4 short prongs at the tip. The seed heads spread into a bristly ball about 1 in (2.5 cm) across.

Look-alikes

BlackjackBidens pilosa

Blackjack's leaves are split into just 3–5 broad, egg-shaped leaflets, while Spanish needles' leaves are finely cut and fern-like. Blackjack's rays are white or absent; Spanish needles has small yellow rays or none.

Why they get mixed upBoth have needle-like, barbed seeds that stick to clothing.

Where it lives

Typical habitats: Woodland edges
Old fields
Roadsides
Vacant lots
Range: Treated as native across much of eastern and central North America, including Illinois and eastern Kansas, plus Arizona; floras in New England consider it introduced there. Many botanists think it is native to Asia as well, and it is now a weed in many warm parts of the world.
Preferred conditions: Grows in partial sun and in damp to average soil, mostly on disturbed ground. In Illinois it is usually found in drier spots than other beggarticks, many of which grow in wetlands.
Flowering: Flowers Aug–Oct
Flowers Aug–Oct