Hogweed is a large plant of the cow parsley family. It grows best in a cool, moist soil in full sun or partial shade. Hogweed often grows in hedges and waste ground in Europe. Common hogweed grows up to 5 feet (1.5 meters) high and has broad, deeply cut leaves. The umbels (umbrella-shaped flower heads) may be white, pink, or purple. The plant gets its name because it used to be a common plant fed to hogs. 
The giant hogweed grows to up to 14 feet (4 meters) high and has white flower heads 3 feet (1 meter) across. Its stem, measuring 2 to 4 inches (5 to 10 centimeters), is hollow and has coarse hairs on the outside. This plant originally grew in the Caucasus Mountains in Russia, Georgia, and Azerbaijan. It was introduced to Europe and North America as an ornamental plant, and now grows wild in many areas. It is an invasive species in these areas today. The sap of the giant hogweed can be dangerous. The active chemicals in giant hogweed sap are activated by sunlight. If the sap touches skin, it can cause a burning rash and painful blisters. Sap touching the eyes can also cause temporary or permanent blindness.
