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Cow Parsnip

cow parsnip's white flower

Cow Parsnip (Heracleum maximum) is native to North America. It grows in a variety of habitats including woodlands, forest openings, grasslands, stream and river edges and along roadsides. Sap contains a phototoxin that reacts with ultraviolet light to cause skin irritation ranging from a mild rash to severe blistering.


It is a biennial, flowering in its second year with a flower stem that may grow more than 6 feet tall. The flower head, made up of numerous small white flowers, is close to a foot across. And the leaves can be almost 2 feet wide. Even the dried seed heads look imposing.

First year plants grow basal rosettes (low clusters of leaves growing directly from the roots) of big coarse hairy leaves divided into 3 deeply lobed leaflets. The leaves have more rounded lobes than the more deeply cut leaves of giant hogweed which usually have more pointed lobes.

Cow parsnip is a big plant and it's easy to believe that it could be hogweed. However, hogweed isn't just big; it's unbelievably huge, a tree-sized herbaceous plant. For a comparison of giant hogweed and cow parsnip, see the DEC web page on giant hogweed identification.

Where is cow parsnip located?

Cow parsnip is relatively uncommon in New York, and tends to be found more often in the cooler parts of the state. Typical habitats are usually near water and in rich, moist soil, often along stream banks, in meadows, and in wet ditches. It also grows well in partial shade along roads, and in floodplain forests. It blooms earlier than giant hogweed, in late May to late June.

If you see a very tall plant with a big flat white flower head, or a basal rosette of very large, hairy leaves (bigger than rhubarb leaves) growing in damp soil, stay clear. However, it is far easier to avoid this conspicuously large plant than it is to avoid the increasingly common wild parsnip which also inflicts nasty burns.

Why is cow parsnip dangerous?

cow parsnip leaf

Possibly the biggest problem with cow parsnip is its close resemblance to giant hogweed. This can alarm people unnecessarily if they find cow parsnip plants, but fear that they are the much more dangerous giant hogweed.

Cow parsnip sap, like that of giant hogweed, contains furanocoumarins (fyur-a-no-coo-MAR-inz), phototoxic chemicals which are activated by ultraviolet rays in sunlight. If sap gets on skin, and is then exposed to sunlight, it can cause a blistering itchy rash. Skin reactions caused by furanocoumarins take a long time to heal, sometimes months, and may even leave scars.

Cow parsnip is not considered to be as toxic as giant hogweed, but like its smaller relative, wild parsnip, it can still cause nasty burns. Unlike the invasive introduced species, giant hogweed and wild parsnip, cow parsnip is native to North America and is found almost everywhere except the south. It is very cold-hardy, and is most abundant in the Pacific Northwest and Alaska, where it has a long history of use as a food and medicinal plant.

cow parsnip with person for scale