Apiaceae : Heracleum maximum
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Family Name
Apiaceae
Common Name
Cow parsnip
Description
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.
Horticulture Notes
Seed collection: Seeds can be collected in late summer and fall when the schizocarps split forming 2 seeds.
Germination: the seeds are dormant and require warm, cold warm treatments to germinate. Plant seed out in late summer and some of them will germinate late in the following spring.
Water: Require very moist sites.
Light: Shade
Soil: Clay, loam or sandy soils, rich in organic matter.
Additional Notes
Cow parsnip is a dramatic plant in a native plant garden. The extremely large leaves and flower clusters are eye-catching. The plants attract birds and butterflies and host swallowtail butterfly larvae. People with sensitive skin can develop rashes with exposure to cow parsnip and it is best to handle this robust plant with gloves.