Native Species Profile - Cow Parsnip

A couple of weeks ago, I posted a photo of the mostly bare seed-head of a Cow Parsnip plant.

Cow Parsnip seed head in Winter - the seeds are consumed by birds

Even in Winter, Cow Parsnip (Heracleum maximum) stands out from its surroundings.  Cow Parsnip is a large plant reaching a height of 4 to 9 feet.  It lives up to its scientific name Heracleum maximum.  Heracleum comes from the Greek word herákleion and refers to the Greek mythological hero Heracles (Hercules); maximum comes from the Latin word magnum which mean "great".  Like the Greek hero, Cow Parsnip dominates its surroundings.

A Cow Parsnip plant in late Summer

Cow Parsnip can be found in moist, low areas across most of North America.  It grows in ditches and streams, along shorelines and riverbanks, and in swamps and other wetlands.  It grows equally well in sun and shade.  It is found in all states except Hawaii and eight states in the Deep South, and in all Canadian provinces and territories with the exception of Nunavut.

Like its namesake garden vegetable, Cow Parsnip is a member of the Carrot Family or Apiaceae.  Like other members of this family it has flat topped flowers.  This type of flower head is called an umbel - a group of small flowers growing in a cluster on short stalks that resemble the ribs of an umbrella.  The flowers are white and bloom between June and August.  The flowers attract many species of butterflies and native bees.

Cow Parsnip - note the umbelliferous flower head

The plant has large compound leaves with three leaflets.  The middle leaflet is further divided into three lobes.  The leaf stalks are swollen and resemble celery stalks - the plant is sometimes known as Indian Celery.  The leaves are attached alternately to the stem and the base of the leaf stalk clasps part way around the stem.  The leaves are soft and were eaten as a cooked green by many Native American tribes.  The leaf stalks and the large hollow stems are covered with fine needle-like hairs.  A word of caution: these needles and the plants sap contain a chemical known as a furocoumarins (furanocoumarins).  This sap can cause a photo-toxic reaction - the sap will react with sunlight causing a chemical burn/rash that can be severe in some people.

Cow Parsnip - note the compound leaf and swollen leaf stalk

Fortunately,  because of its size it is easy to avoid accidental contact with Cow Parsnip.  It often towers over any surrounding vegetation.  Nor can it be easily confused with any other native plants.  At some stages of growth it does resemble other native Apiaceae species, but a mature Cow Parsnip towers over these other plants.  It does resemble other Heracleum species including Heracleum mantegazzianum.  Also known as Giant Hogweed, H. mantegazzianum has been introduced to some 
areas of North America and is considered a noxious weed.  The sap from Giant Hogweed causes an even more severe photo-toxic reaction than Cow Parsnip.

Cow Parsnip growing in a Northern Hardwood-Conifer Swamp

Basic Information

Cow Parsnip 
Heracleum maximum (Heracleum lanatum)

Height:  4-9’ tall

Habitat:  low, moist areas;  roadsides, shorelines, along banks

Flower Color:  white to purplish

Bloom Time:  June – August