Whoa, this plant will catch your attention! Although towering in at up to 8 feet tall with leaves 2 feet wide, Cow parsnip (Heracleum maximum, aka Heracleum lanatum) is not a tree, but herbaceous (non-woody). This species is the largest member of the carrot family (Apiaceae) native to North America. It can be found along shaded roadsides, waterways, and edge of woods. Its flower structure consists of many small white flowers on short stalks connected at a single point – an umbrella of flowers – botanically known as an “umbel.” Umbels are characteristic of the carrot family (think of the perhaps better recognized Queen Anne’s lace, Daucus carota, which is also known as “wild carrot”).
These specimens were all collected on June 21 – but years apart in 1907 (Westmoreland county, PA), 1934 (Pittsburgh), and 1960 (Beaver county, PA).
This species is often confused with giant hogweed. Cow parsnip is often confused for the non-native plant called giant hogweed (Heracleum mantegazzianum). Giant hogweed has hit the news media in the past few years and is on many people’s radar, as it is considered a significant public human health concern. This plant is highly poisonous and designated as a federal noxious weed. The sap of giant hogweed causes “phytophotodermatitis,” meaning serious skin inflammation occurs when contacted skin is exposed to sunlight. Skin rashes can be very severe. The sap can cause temporary or permanent blindness. Cow parsnip has a similar set of chemicals in its sap, and although not as poisonous, be careful around these plants.
Giant hogweed can be 8-20 feet tall with leaves up to 5 feet wide! It is thought to be eradicated in Pennsylvania. Although similar to the Pennsylvania native species cow parsnip, giant hogweed is noticeably larger in height and flower size. (see herbarium specimen here – it took 6 sheets!)
Given the size of members of the genus, the name Heracleum (derivative of Hercules) is quite fitting.
Specimen records and images for this species in the CM herbarium are now publicly available online.
Check back for more! Botanists at the Carnegie Museum of Natural History share digital specimens from the herbarium on dates they were collected. They have embarked on a three-year project to digitize nearly 190,000 plant specimens collected in the region, making images and other data publicly available online. This effort is part of the Mid-Atlantic Megalopolis Project (mamdigitization.org), a network of thirteen herbaria spanning the densely populated urban corridor from Washington, D.C. to New York City to achieve a greater understanding of our urban areas, including the unique industrial and environmental history of the greater Pittsburgh region. This project is made possible by the National Science Foundation under grant no. 1801022.
Mason Heberling is Assistant Curator of Botany at the Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.