Giant Hogweed

Giant Hogweed is a member of the carrot and parsley family and native to the Caucasus region of Europe and Asia. Giant Hogweed was introduced to Great Britain as an ornamental showpiece in the 1800s for its unique size and flower head. It was later transported into North America as a showpiece in arboretums and Victorian gardens with the first plantings found near Highland Park in the City of Rochester, New York.

Giant Hogweed is a perennial herb with tuberous roots that survives season to season by forming perennating buds and enduring dormancy during the winter months. The plant grows numerous white flowers that form a flat, umbrella-shaped head that can reach two and a half feet across resembling Queen Anne’s Lace. Giant Hogweed produces about 100,000 seeds from the flower head in late summer which are about half an inch long and can spread through animals, surface runoff or wind. These seeds can remain viable in the soil for up to ten years. The stems of Giant Hogweed are typically three to four inches in diameter and hollow. They produce large lobed, deeply incised compounded leaves that can reach five feet in width. Giant Hogweed can grow as tall as 15 to 20 feet high.

Giant Hogweed is found in a wide range of habitats with a preference to damp, nutrient rich soil that may be found along abandoned railroads, roadside ditches, stream banks or other similar areas. In New York State, several native plants can be mistaken for Giant Hogweed such as native Cow parsnip, wild parsnip, native Purple-stemmed angelica, and Poison hemlock.

This invasive plant uniquely impacts both human and ecological health. Because of Giant Hogweeds seed production and growth rate, colonies of Giant Hogweed can be produced fairly quickly. A dense stand of Giant Hogweed crowds out slow-growing and shorter plants which can displace native plants that need direct sunlight. A reduction of native plants in the landscape will reduce the use of the habitat for wildlife and can cause stream bank erosion.

In terms of human health, Giant Hogweed sap can cause a significant reaction with direct contact to the skin. The sap from a broken stem or crushed leaf, root, flower or seed that comes into contact with the skin and later exposed to sunlight, will cause a form of dermatitis due to the glucoside present in the sap. This glucoside is a psoralen that is sensitive to UV rays which can result in severe burns, blistering, painful sores and or purplish or blackened scars to the affected area. This reaction will appear within one to three days after exposure.

The health impacts of this invasive species have landed it on the federal noxious weed list. In terms of control and removal methods, Giant Hogweed can be difficult to eradicate. Some methods to control and eradicate Giant Hogweeds presence include bio grazing by cows and pigs, mowing and cutting for small areas, digging out for individual specimens as well as the use of herbicides have proven effective. In all methods, extreme precautions should be taken in terms of protective clothing and eye protection to prevent skin contact.


Giant Hogweed-Poisonous Invader of the Northeast [PDF], This document created by New York Sea Grant highlights this invasive species and details its relevant background information, common look-alikes, identifying characteristics, control methods and impacts to the ecosystem and human health.

Giant Hogweed- Do Not Touch This Plant, This webpage from the New York State Department of Environmental Conservation provides relevant information about this species including how to report sightings, information on the DEC’s Giant Hogweed Control Program and materials to spread awareness about Giant Hogweed.

Giant Hogweed- Health Advice, This webpage from the New York State Department of Health documents helpful information on what to do if you have contact with Giant Hogweed.

Last updated December 13, 2023