Cow parsnip: Important Native or Nemesis?

Cow parsnip is known by many names. Scientifically it is referred to as Heracleum maximum, but for centuries it has been known by indigenous people across North America as pipigwe’wanuck, okintsomo, yazobi, gistem, sol, gwas, ggis, pushki (Journal of Ethnobiology).

All across North America cow parsnip is revered by indigenous peoples for its medicinal and edible qualities. The roots are commonly ground into a powder and applied to joints to ease pain. The Quinault word for cow parsnip, wak√°, means ‘kills the pain’. From April to late June, cow parsnip is harvested and eaten. The soft pith, once removed from the inner stem, is eaten.

Humans are not the only species to feed on cow parsnip! The leaves are an important food source for cow parsnip thrips and parsnip webworm moth larvae. Dozens of bee, wasp, fly, and butterfly species also visit the flowers of cow parsnip.

Pollinators on cow parsnip along the Paint Creek Trail in 2021. Photo by Ben VanderWeide.

A Case of Mistaken Identity

Cow parsnip is also often referred to as a ‘dangerous plant.’ How did this come to be, when cow parsnip has been an important aspect of cultures for centuries? It’s often a mix up between two species: cow parsnip (Heracleum maximum) and giant hogweed (Heracleum mantegazzianum). To be fair, they are ‘siblings.’ They both come from the carrot family, Apiaceae, and within that family they belong to the same genus, Heracleum.

Why are are folks rightly concerned about giant hogweed? It is an invasive species hailing from western Caucasus. Like most plants within the genus Heracleum, and other members of the carrot family, it can cause photodermatitis, a condition in which skin will blister, swell, and scar when sap gets on the skin and is then exposed to sunlight. Giant hogweed is infamous for these effects, and causes extreme expression of these symptoms. You should also avoid the sap of wild parsnip (Pastinaca sativa) and poison hemlock (Conium maculatum), two other species in the carrot family that cause photodermatitis. Click here to view a a great card from the Oakland County CISMA comparing these four species.

The sap of our native cow parsnip is still phototoxic, but its effects are far milder. When handled carefully, cow parsnip has been safely consumed and appreciated for centuries. Giant hogweed, on the other hand, does not have the same rich culinary and medicinal history across the United States.

Unfortunately for our beloved cow parsnip, the two plants do look similar. Each year we receive reports of potential hogweed along the Paint Creek Trail, where it grows happily in its favored floodplain and wet meadow habitat. When a potential sighting is reported we check each one. So far we’ve only found cow parsnip. In fact, no giant hogweed has been found yet within Oakland County. There are several key differences between the two species.

Height

The most obvious difference is height. Giant hogweed is… giant! At maturity it can reach up to twenty feet high. Cow parsnip on the other hand, caps out at around seven feet.

Umbel

The flower head, or umbel, of cow parsnip is flat. Whereas the umbel of giant hogweed is rounded in appearance.

Stem

The stems of cow parsnip are a uniform shade of light green, whereas giant hogweed stems are splotched with wine colored markings.

Leaves

The leaves of cow parsnip are also more rounded in appearance than giant hogweed. Giant hogweed has deeply lobed leaves.

We worked with the Paint Creek Trail a few years ago to develop a helpful poster comparing the two species.

A Note on Poisonous Plants

When a plant is labelled poisonous, it is alarming. However you may be surprised at how well we coexist with the world of plant toxins (phytotoxins). Plants are (mostly) stationary forms of life. In order to protect themselves from predators, and from competition with each other, they had to adapt defenses. These defenses can take the physical form of spines on cacti, or waxy leaf cuticles that protect against plant pathogens. The less visually apparent defenses are the chemical defenses that lead to phytotoxicity.

A photo of swamp milkweed (Asclepias incarnata).

The beloved milkweed is a great example of our harmony with phytotoxins. We adore milkweed. Its blooms are a fragrant addition to our plant beds, and they bring with them a host of diverse pollinators. Would you be shocked to learn that every part of milkweed is poisonous? Every part of the plant, from root to petals, contains cardiac glycosides. These compounds can cause some serious and nasty effects. In spite of this, we adore milkweed.

Another example are the twigs and pits of cherries, which are rife with a cyanide releasing compound. Foxglove, cashews, rhubarb, iris, oaks, apple and apricot seeds, kidney beans… All contain a poisonous component! When approached with care and knowledge, poisonous plants are nothing to fear. They play important roles in our ecosystems, benefitting the smallest insect to the hungriest stomach via our dinner plates.

The umbel of cow parsnip post-flower, with immature seeds beginning to grow.

So when you come across cow parsnip in the wild, take a moment to appreciate its beauty. Express caution and not fear. Admire the leaf miners munching along the large leaves, creating a mosaic of tunnels in their wake. Take notice of the huge umbel (currently setting seed) that attracted dozens of pollinators just a few short weeks ago. Recall its rich history. Fantasize about the smell of a thick stew in early spring… Bubbling with the sweet, peppery flavor of young cow parsnip shoots.