Bidens bipinnata - Spanish Needles

Spanish Needles is an annual herb about 2-5 ft tall. It is more or less erect and branches occasionally. The stems are green or reddish green, angular, strongly veined, and hairless (or nearly so). The leaves are mostly opposite, up to 8 inches long and 4" across, while the stalks are up to 2 inches long. Leaves are double- or triple-compound, medium green, and hairless (or nearly so). The segments of the blades are ovate, lanceshaped, or oblanceolate with blunt tips and wedge-shaped bottoms; the margins of these segments are irregularly cleft or toothed. Overall, the leaf blades have a fern-like appearance. The upper stems terminate in individual flower-heads on long stalks. Each flower-head is about 1.2 cm long and 6 mm across. It has numerous disk florets in the center and 0-5 ray florets along its upper margin. The disk florets have corollas that are golden yellow and tubular in shape; each corolla has 5 tiny lobes along its upper rim. The yellow ray florets are petal-like; they are about 1/8" long and oval to oblong in shape. Some flower-heads may lack petal-like extensions of the ray florets altogether. The base of the flower-head is surrounded by green bracts; the linear inner bracts are much longer (about 1/3" in length) than the outer bracts. Each flowerhead is replaced by a seedhead that is globoid in shape and spans about 1 inch across. The long narrow seeds (achenes) spread outward from the center in all directions. Each mature seed is linear in shape, 4-angled, and dark brown; it has 2-4 short awns at its tip. Each tiny awn has downward-pointed barbs. Spanish Needles is naturalized worldwide, probably native to the American continents.