Apiaceae : Heracleum maximum

Heracleum maximum is a tall perennial herb reaching heights of 3 m, with hollow stems that are densely hairy , erect, with few to many branches. The lower compound leaves are ternate and softly hairy, with fine sharp teeth along the margins, very large, 20-50 cm long and equally as wide, becoming smaller as they ascend the stem. The leaflets are ovate 15-40 cm long and 10-35 cm wide, cordate with petioles 10-40 cm long. The end leaflet is largest and lobed in 3 parts; each lobe may be further divided. Leaf attachment is alternate, and the petioles clasping and sheathed. The inflorescence is a compound umbel that can reach 30 cm in diameter, flat-topped or rounded, composed of small white flowers. Individual flowers are about 6mm across with 5 white petals that are notched at the tip, the outer flowers being much larger than the inner ones. There are 5 white tipped stamens. A plant may have few to many flower clusters growing from the tips of branching stems and arising from the upper leaf axils. The fruit are schizocarps 8-12 mm long and 6-9 mm wide, strongly flattened dorsally. Cow parsnip flowers in May, June and July in moist woods, along streams and in thickets in both eastern and western South Dakota.