Heracleum sphondylium L.

Cow Parsnip

© SRTurner

Family - Apiaceae

Habit - Taprooted perennial forb.

Stem - Erect, stout, ridged, to 2 m, sparsely to densely pubescent with spreading hairs.

	Stem and leaf sheath.
© SRTurner

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.

	Basal leaf.
© SRTurner

	Basal leaf abaxial.
© SRTurner

	Leaf and sheath.
© DETenaglia

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.

	Inflorescence.
© SRTurner

	Involucel.
© SRTurner

	Umbellet.
© SRTurner

Florets - Numerous in each umbellet, on stalks to 12 mm long. Petals obovate, white, sometimes larger near edge of umbellet. Ovaries hairy.

	Florets.
© SRTurner

Fruits - To 12 mm long, oblong-obovate, flattened, sparsely hairy, tan with darker oil tubes between ribs.

	Fruits.
© SRTurner

Flowering - May - July.

Habitat - Bottomland forests, ravines.

Origin - Uncertain.

Lookalikes - None.

Other info. - This coarse, giant plant is uncommon in Missouri, found in only a few widely scattered counties. It is more common elsewhere and is found in most U.S. states, except for the far south. It is quite common in some areas, e.g. in portions of the Rockies. The plant is easily recognized by its large, coarse stems with greatly distended petiole sheaths, and giant compound umbels of white florets. The gigantic stature and coarse nature often attained by these plants make the term "cow parsnip" seem somehow appropriate.

Authors such as Steyermark have treated American plants as a distinct species, H. maximum, but differentiation from the Eurasian H. sphondylium is uncertain. Contact with the plants should be avoided, due to their content of furanocoumarins which render them phototoxic. Sap residues on the skin, if exposed to sunlight, can cause potentially serious rashes and blistering. The closely related H. mantegazzianum (giant hogweed) has gained notoriety in Europe and a few northern U.S. states due to the severe photodermatitic reactions it can cause. Hospitalizations can result and the scarring can persist for years.

Photographs taken at Shaw Nature Reserve, Franklin County, MO, 5-25-2014 and 6-20-2014 (SRTurner).