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Giant Hogweed

Heracleum mantegazzianum  Sommier & Levier

Apiaceae (Carrot Family)

▲▼ seedlings, young plants

▲▼ seedlings, young plants

 

▲▼slightly older plants

 

▲▼ mature plants, ready to flower

▲▼purplish speckling in ridges and hairy stems

▲▼purplish speckling in ridges and hairy stems

 

▲ large mature leaf (note U.S. dime just below and right of center picture sitting on leaf)

 

▲ hollow flowering stem (above photo by Mike Sallee) 

▲ uprooted crowns (still trying to grow)

▲ regrowth from where the crowns had been dug

▲ plant initiating flowering

 

▲▼ mature, flowering plants (above and below photos by Mike Salli) 

 

▲▼ mature, flowering plants (above and below photos by Mike Salli) 

 

▲▼ mature, flowering plants (above and below photos by Mike Salli) 

 

 

▲ inflorescence starting to form seeds (above photo by Mike Salli)

 

▲▼ seed forming on inflorescence (above and below photos by Mike Salli)

 

 

Heracleum mantegazzianum Sommier & Levier.; Giant Hogweed: (Bayer Code:  HERMZ; US Code HEMA17)

        ·         Herbaceous short-lived perennial in the Carrot Family (Apiacaeae) that lives 2-5 or more  years, producing a rosette of very large, tripartite leaves with toothed margins; leaves are hairy and can be up to 3 feet or more in diameter

        ·         Leaf stems and flowering stems have purple speckling (usually in rows) and moderate to dense fine, straight hairs

        ·         Plants can grow 10-15 feet tall or larger

        ·         Flowers are at stem tips in very large, multi-part umbels of many small white to creamy-white flowers

        ·         Leaf stems are hollow

        ·         Dangerous plant in that sap from plants can cause blistering of skin, once exposed to sunlight after contact with the sap; sap can remain on implements, gloves for a long time—need to wear protective clothing, goggles when in contact with it

        ·         Native to Europe, planted in U.S. as a horticultural curiosity (giant plant), but has escaped and become invasive in cooler, moister parts of U.S.—particularly around Great Lakes areas

        ·         Is declared a Federally noxious weed, so is controlled by government agencies where found

        ·         Appears similar to U.S. native cow parsnip, but cow parsnip lacks the purple speckling, often has more fine white hairs on stems and leaf stems, and  usually is about 3-6 feet tall

 

Much thanks to Jim Finley, Erin Ross, Mike Salli, Susan Trull, Zach Wilson for their help in providing locations to photograph this weed in Wisconsin and Michigan.

 

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Updated 15 January 2019