PlantFiles: Giant Hogweed
Heracleum mantegazzianum

The stems are green with reddish speckling, but hard to confuse with similar plants on account of its size. In the UK this plant is far less common than the much smaller regular hogweed. I found a large clump of this growing on a former dumping ground for green waste, now derelict & overgrown. The large leaves create deep shade below in which almost nothing grows. Plants growing in shade are smaller than those in sunny positions.
Where clumps grow they die off in autumn,leaving behind messy looking bare patches in winter, littered with dead stalks and pitted with holes where the stems of the previous years plants grew. This plant never seems to grow in balance with surrounding vegetation, it tends to completely take over the places that it invades.

Giant Hogweed Heracleum mantegazzianum is naturalized in Texas and other States and is considered an invasive plant in Texas,

U.S. FEDERALLY LISTED NOXIOUS WEED.
Not allowed for import to the US and not allowed in any interstate or intrastate transportation without a specific permit from USDA APHIS PPQ (Plant Protection and Quarantine).

The synonyms above are wrong. There are several distinct species of Heracleum. Heracleum persicum is used as a spice in the middle east, particularly Iran. The seeds are ground to flavour food (golpar). Very worthwhile plant to grow for collectors of ethnobotanical specimens.

WARNING: Irradicate this dangerous noxious pest wherever possible. Please put a strong warning in your description. A year ago I didn't know what this was and now I have permanent scars as a result of cutting it along a bank. It caused HUGE blisters (several inches long) all over my arms and hands and even on my legs where it touched as I picked it up. Now, a year later whenever the scars are in sun even briefly they burn and itch. Please read medical descriptions on the [HYPERLINK@www.] I WAS LUCKY! This plant can either temporarily or permanent BLIND you if the sap gets in your eyes. Don't let the sap get on you. Don't burn the plant as the toxic chemical will be airborne in the smoke.

This plant should not be cultivated. It is invasive and the sap can cause severe burning when the skin is exposed to sunlight after contact. By burning i mean large and very painful blisters. It can be even more serious if contact is made with the eyes or sensitive places such as the mouth.

I would urge you to avoid this plant.

A member of the parsley or carrot family.As its name indicates it is characterized by its size and may grow to 15 to 20 feet in height.It has a stout dark reddish-purple stem and spotted leaf stalks. Stalks and stem produce sturdy pustulate bristles. The stem and stalks are hollow, stems vary 2 to 4 inches in diameter. The compound leaves of giant hogweed may expand to five feet wide. Each leaflet is deeply lobed. Giant hogweed is a perennial with tuberous root stalks which form perennating buds each year. The bloom is a broad flat-topped umbel composed of many small white florets. Each bloom may reach a diameter of 2-1/2 feet. The plant exudes a clear watery sap which sensitizes the skin to ultraviolet radiation. Giant hogweed is currently on the federal noxious weed list.