Heracleum sphondylium L. ssp. montanum Briq.
Family - Apiaceae
Stem - Erect, stout, ridged, to 2 m, sparsely to densely pubescent with spreading hairs.
Stem and leaf sheath.
Leaf - Alternate and usually basal, petiolate. Petioles densely pubescent, with base sheathing and strongly inflated. Blades broadly ovate to circular in outline, lobed or ternately compound, pubescent, toothed on margins.
Leaf and sheath.
Inflorescence - Terminal and axillary compound umbels. Involucre of 5-10 bracts to 2 cm long, hairy, deciduous. Rays numerous, 5-10 cm long, unequal in length, hairy. Involucel of 4-10 bractlets, hairy.
Florets - Numerous in each umbellet, on stalks to 12 mm long. Petals obovate, white, sometimes larger near edge of umbellet. Ovaries hairy.
Fruits - To 12 mm long, oblong-obovate, flattened, sparsely hairy, tan with darker oil tubes between ribs.
Flowering - May - July.
Habitat - Bottomland forests, ravines.
Origin - Uncertain.
Other info. - Authors such as Steyermark have treated American plants as a distinct
species, Heracleum maximum, but differentiation from the Eurasion Heracleum sphondylium is uncertain.
Under favorable conditions these plants can become coarsely gigantic, making the term "cow parsnip" seem somehow appropriate. Contact
plants should be avoided, since the plants contain furanocoumarins which render them phototoxic. Exposure to the sap and
then sunlight can cause potentially serious rashes and blistering.
Photographs taken at Shaw Nature Reserve, Franklin County, MO, 5-25-2014 and 6-20-2014 (SRTurner).