Cow parsnip at Matthaei.

Cow parsnip leaf.

Cow parsnip plant and leaves.

Cow parsnip leaf edges.

By Katie Stannard
This week’s native plant is cow parsnip, Heracleum maximum. Dramatically tall to 8’ and topped with a bright beacon of florets, it’s definitely an attention-getter–whether of alarm or admiration. 
Part of the carrot family (Apiaceae), common names include Indian celery, Indian rhubarb, American cow parsnip, and pushki. 
Cow parsnip contains chemicals called furanocoumarins which can irritate skin, causing rashes and burn-like lesions–depending on one’s sensitivity–after affected skin has been exposed to ultraviolet light (like sunlight). It’s thought that these phytochemicals act as a defensive protection against some detrimental insects, mammals, and fungi.
When entering skin tissue nuclei, phytochemicals bridge with the DNA when exposed to sunlight, causing cell death and a type of inflammation known as phytophotodermatitis. Furanocoumarins are also found in citrus, with positive impacts found in grapefruit, and include anti-inflammatory, anti-obesity, and anti-cancer effects.    
Many ethnobotanical uses by Native American peoples are documented. Stalks could be peeled and eaten raw, or cooked, made into flutes, used as straws, and employed for ceremonial purposes. Leaves were crushed for a drink to aid sore throats or colds. Roots were utilized in compounds for a variety of topical remedies to help with bruises, swelling, pain, rheumatism, toothaches–which sound like the anti-inflammatory properties related to bergapten and psoralen, now known as linear furanocoumarins endemic to the Apiaceae family.

Cow parsnip flowers close up.

Cow parsnip seed head.

Cow parsnip purple veining.

Cow parsnip fine hairs.

Native to a large swath of North America from Georgia to the southern half of California northward, cow parsnip is found in forest edges, floodplains, along wet meadows, river banks, and the open areas of clearings and hardwood forests. Fun fact: it’s found up to 9000 feet in elevation. 
Distinctive June-blooming flowers appear in flat-topped clusters along hairy, hollow stems, emerging from purple-veined, enlarged sheaths at the base of the leaf stalks. Large maple leaf-shaped compound leaves with sharply toothed edges grow to 2.5’ across; fine hairs give it a softer appearance. Leaves are ternately (meaning 3 parts) divided. End leaves are the largest and may have additional divisions. Like other carrot family members, cow parsnip has a deep taproot supported by other roots. 
Broad clusters or umbels of flowers are 8” across. Each umbel has 20-30 smaller clusters (umbellets) with up to 30 ¼” notched white flowers. Flat fruits are oval to heart-shaped, roughly ¼-½” long. At maturity the seed turns brown and then splits open into two. 
With many tiny flowers, cow parsnip is an excellent source of pollen and nectar for many insects, including species of bees, wasps, gnats, flies, and beetles. It’s a larval host for the anise swallowtail, and consumed by deer, livestock, and moose.
Cow parsnip is a striking plant in natural settings, or in a native plant garden or border. Because the amount of phytochemicals in plant parts varies–and one’s sensitivity to them is unknown–it’s essential to wear sturdy gloves and pants when working with or hiking in areas with a lot of cow parsnip. If bare skin is touched by the plant, it’s advised to wash the area with soap and water and avoid exposing it to the sun for 48 hours.
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