Cow Parsnip

Cow parsnips are not related to the root vegetable known as parsnips, but you can eat them, if you are careful.

Nine-foot tall cow parsnips in Alaska (Beeblebrox) CC BY-SA 4.0

Cow parsnip description

True to its Latin name, Heracleum maximum, these are very large herbaceous plants. Reaching over 9’ in height, all parts of cow parsnip are big. Lobed leaves can be 16” across and the typical umbel-shaped flowers of the carrot family are also large, averaging 8” across. These flowers are white and the outer flowers are often larger than the inner flowers. Stems are succulent and sturdy. ​

Cow parsnip seeds (Walter Siegmund) CC BY-SA 3.0

Cow parsnip plants (Dcrjsr) CC BY 3.0

Uses for cow parsnip

Peeled flower stems have been used as food for a very long time. Tasting similar to celery, cow parsnip is also known as Indian celery or Indian rhubarb. The reason for peeling those stems is because the outer layers contain phototoxins that can irritate or burn your skin. Traditionally, infusions of the flowers were used to repel flies and mosquitoes. Before you start rubbing yourself with cow parsnip, be sure to take a closer look. If you see reddish or purplish spots on the stems, and serrated leaves, look out! You have discovered giant hogweed, a far more potent version.

Giant hogweed

Purple spots and serrated leaves may indicate giant hogweed (Heracleum mantegazzianum), rather than cow parsnip. The sap of giant hogweed contains phototoxins. These defensive oils cause severe burns and blisters when exposed to light.

Giant hogweed red-spotted stem (I, Liné1) CC BY-SA 3.0

Giant hogweed (Fritz Geller-Grimm) CC BY-SA 3.0

Now, I am not talking about the discrete round blisters of sunburn fame. These are huge, swollen, ugly, painful burns that can leave black or purple scars for years to come. I won’t share photos here, but you can track them down yourself if you need convincing.

​This dangerous sap is found on coarse white hairs (trichomes) on stems. It can cause third-degree burns serious enough to land you in the hospital or a burn unit. Giant hogweed has found its way to northern U.S. states. If you see it, report it to your local County Extension Office.

Another toxic plant commonly mistaken for cow parsnip is poison hemlock, also with purple marks on the stem. Bottom line: when in doubt, don’t.

Since cow parsnip, giant hogweed, and poison hemlock can all hurt you, to one degree or another, it is a good idea to be cautious and wear protective clothing whenever you might be around them.