Heracleum maximum – Common Cowparsnip

Heracleum maximum - Common Cowparsnip, Cow Parsnip, Cow-parsnip

Heracleum maximum - Common Cowparsnip, Cow Parsnip, Cow-parsnip

Heracleum maximum - Common Cowparsnip, Cow Parsnip, Cow-parsnip

Plant Name

Scientific Name: Heracleum maximum

Synonyms: Heracleum lanatum, H. sphondylium ssp. montanum, H. sphondylium var. lanatum

Common Names: Common Cowparsnip, Cow Parsnip, Cow-parsnip

Plant Characteristics

Duration: Perennial

Growth Habit: Herb/Forb

Arizona Native Status: Native

Habitat: Mountain, Riparian. These large, attractive wildflowers grow in moist, shady to partly shady mountain woodlands and along mountain streams.

Flower Color: White

Flowering Season: Summer

Height: Up to 8 feet (2.4 m) tall, but usually less

Description: The small, white flowers are in large, 6 to 12 inch (15 to 30 cm) wide, round-topped or flat-topped compound umbels. The individual flowers have 5 shallowly to deeply notched petals, 5 sepals, and 5 stamens. The flowers are followed by flat, green, egg-shaped to somewhat heart-shaped fruits with a parsley-like scent. From a distance, the fruit umbels look like green flowers. The leaves are basal and alternate, round to kidney-shaped, and ternate with 3 dark green, toothed and lobed main lobes. The stems are green, densely hairy, and hollow inside.

This is the only Heracleum species found here in Arizona.

Special Characteristics

Foul-smelling – The foliage has an unpleasant smell.

Fragrant – The flowers are fragrant.

Poisonous – This plant contains various phototoxic furocoumarins that can make the skin (especially light skin) extremely sensitive to sunlight and prone to sunburn. Skin contact with juice from the plant followed by exposure to sunlight can cause photodermatitis, which can range from a mild, red rash to severe skin blistering. Wear gloves when cutting or weeding this plant, promptly wash off any sap, and keep any affected areas out of direct sunlight. Merely touching this plant should not cause any harm because the phototoxins are in the sap.


Kingdom: Plantae – Plants
Subkingdom: Tracheobionta – Vascular plants
Superdivision: Spermatophyta – Seed plants
Division: Magnoliophyta – Flowering plants
Class: Magnoliopsida – Dicotyledons
Subclass: Rosidae
Order: Apiales
Family: Apiaceae – Carrot family
Genus: Heracleum L. – cowparsnip
Species: Heracleum maximum Bartram – common cowparsnip

More About This Plant

Arizona County Distribution Map
Common Cowparsnip (Heracleum maximum) – The Firefly Forest