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Heracleum mantegazzianum

Heracleum mantegazzianum Sommier & Levier

 

Giant Hogweed, Cartwheel-flower, Wild Parsnip, White Rhubarb, Giant Cow Parsnip, Giant Cow Parsley

KingdomPlantaePlants, but not fungi, lichens, or algae
SubkingdomTracheobiontaVascular plants—plants with a “circulatory system” for delivering water and nutrients
DivisionMagnoliophytaFlowering plants, also known as angiosperms
ClassMagnoliopsidaDicotyledons—plants with two initial seed leaves
SubclassAsteridaeA large class that encompasses asters
OrderApialesIncludes carrots, celery, parsley, and ivy
FamilyApiaceaeCarrot or parsley family, also includes angelica, anise, caraway, celery, chervil, cicely, coriander/cilantro, cumin, dill, fennel, hemlock, lovage, Queen Anne’s Lace, parsnip
GenusHeracleumNamed for Hercules, either because he used a species for medicine or because, like Hercules, some species are very large
SpeciesmantegazzianumFor 19th century Italian etnographist (sociologist/anthropologist) Paolo Mantegazzi

About plant names...

The Return of the Giant Hogweed. Sounds like a good name for a horror movie, but it is actually a song by Genesis that satirizes the spread of this plant. It really is a scary plant, reaching as high as 23' (7 m), and armed with poisons that can cause blindness or permanent scarring. This species is listed in the 2003 Guinnesss Book of World Records as the world’s largest weed. Ironically, it is not a native of western Europe or North America; it was introduced as an ornamental. Introduced? That’s like bringing, say, Burmese pythons to south Florida and having them take over the Everglades, eating 90% of the local mammals. Oh, wait, that actually happened...

 

Heracleum mantegazzianum (Giant Hogweed, Cartwheel-flower, Wild Parsnip, White Rhubarb, Giant Cow Parsnip, Giant Cow Parsley)

7/7/2017 · OR · By Tim Butler, Oregon Dept. of Agriculture

Heracleum mantegazzianum (Giant Hogweed, Cartwheel-flower, Wild Parsnip, White Rhubarb, Giant Cow Parsnip, Giant Cow Parsley)

7/7/2017 · OR · By Tim Butler, Oregon Dept. of Agriculture

Heracleum mantegazzianum (Giant Hogweed, Cartwheel-flower, Wild Parsnip, White Rhubarb, Giant Cow Parsnip, Giant Cow Parsley)

7/7/2017 · OR · By Tim Butler, Oregon Dept. of Agriculture

Here are some similar-appearing species:

  You are here
Heracleum mantegazzianum

Heracleum maximum

Daucus carota
Common Name

Giant Hogweed

Cow Parsnip

Queen Anne’s Lace
Plant Extremely large: 6½-16' (2-5 m) tall, sometimes reaching 23' (7 m). Poisonous Skull & Crossbones: causes phytophotodermatitis. Up to 6½' (2 m) in height. Poisonous Skull & Crossbones: causes phytophotodermatitis. Grows to 3’ in height. Plant smells like carrots.
Flowers White flowers form flat-topped compound umbels (flowerheads) up to 30" (76 cm) in diameter. Large white compound umbels about 8" (20 cm) in size. Individual flowers have five petals of inconsistent size. Pale pink before opening. When open, forms an umbrella-shaped flower cluster up to 3” across, composed of tiny 5-petaled flowers.
Leaves Leaves are up to 5' (1.5 m) across, extensively divided into sharp-tipped sections. Up to 16" (40 cm) across, split into sharp lobes that vaguely resemble maple leaves, with a disagreeable odor. Compound leaves are deeply divided and subdivided.
Stem Hollow stems are 1-4" (3-10 cm) in diameter, with deep purple raised blotches containing white hairs. Thick, grooved, hollow, hairy, and often reddish. Fine hairs on stems and leaves.
Seeds Each seed is up to ¼" (8.3 mm) long.    
Fruit   Flat, green, egg- or heart-shaped, ⅜-½" (9.5-12 mm) × ¼-⅜" (6.3-9.5 mm).  
Range/ Zones

Habitats Rich, moist soils in ditches, stream banks, vacant farmland, and fence and tree lines Moist, shady mountain woodlands, streambeds  
Type Wild Wild Wild
Occurrence     Common

 

Identification: These plants are annuals, making it all the more amazing that they routinely grow to a height of 6½-16' (2-5 m) and sometimes reach 23' (7 m) in a single growing season. Hollow stems are 1-4" (3-10 cm) in diameter, with deep purple raised blotches containing white hairs. Leaves are up to 5' (1.5 m) across, extensively divided into sharp-tipped sections. White flowers form flat-topped compound umbels (flowerheads) up to 30" (76 cm) in diameter. A single plant produces 20,000 oval seeds, each up to ¼" (8.3 mm) long. Giant hogweeds look most similar to extra large versions of common hogweed (Heracleum sphondylium), or Sosnowsky’s hogweed (Heracleum sosnowskyi), or garden angelica (Angelica archangelica). If you don’t know what any of those look like, they also look a bit like ”Queen Anne's lace on steroids,” as one botanist quipped. Here is a good comparison of several similar species.

Edibility: Poisonous Skull & Crossbones These plants contain furocoumarins in their sap, a defense against fungal attack. It happens that these chemicals cause phytophotodermatitis in people—that is, severe skin blistering from exposure to light. If you come in contact with the plant, then are exposed to long wave ultraviolet light (sunlight), the dermatitis develops. The exposed skin becomes bright or dark red, developing large blisters. The effects resemble chemical burns, and can leave permanent discoloration or scarring. Temporary or permanent blindness can result from eye exposure.

Removal: Don’t try to remove this plant yourself. Call the local Department of Agriculture and have it removed by professionals (or perhaps the Men in Black). Giant hogweed is federally listed as a noxious weed in the United States, so it is illegal to import, export, transport, or (presumably) grow this plant without a permit.

Online References:

Heracleum mantegazzianum on luirig.altervista.org

Heracleum mantegazzianum on www.oregon.gov

Heracleum mantegazzianum on Wikimedia Commons (Many photos)

Heracleum mantegazzianum on ohioline.osu.edu

Heracleum mantegazzianum on Wikipedia

Heracleum mantegazzianum at the USDA National Invasive Species Information Center

Heracleum mantegazzianum on the USDA Forest Service's Fire Effects Information Database

Heracleum mantegazzianum on www.nrs.fs.fed.us (PDF)

Heracleum mantegazzianum on www.seagrant.sunysb.edu (PDF)

Heracleum mantegazzianum description by Thomas H. Kent, last updated 16 Aug 2013.

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