Heracleum mantegazzianum (Giant hogweed)

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Heracleum mantegazzianum Sommier & Levier

Giant hogweed, cartwheel-flower, wild parsnip, white rhubarb, giant cow parsnip, giant cow parsley

Kingdom	Plantae	Plants, but not fungi, lichens, or algae
Subkingdom	Tracheobionta	Vascular plants—plants with a “circulatory system” for delivering water and nutrients
Division	Magnoliophyta	Flowering plants, also known as angiosperms
Class	Magnoliopsida	Dicotyledons—plants with two initial seed leaves
Subclass	Asteridae	A large class that encompasses asters
Order	Apiales	Includes carrots, celery, parsley, and ivy
Family	Apiaceae	Carrot or parsley family, also includes angelica, anise, caraway, celery, chervil, cicely, coriander/cilantro, cumin, dill, fennel, hemlock, lovage, Queen Anne’s Lace, parsnip
Genus	Heracleum	Named for Hercules, either because he used a species for medicine or because, like Hercules, some species are very large
Species	mantegazzianum	For 19th century Italian neurologist, physiologist, and 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...

Ridges and coarse hairs on hollow stem of giant hogweed. PA Dept. of Agriculture. · 7/29/2023

7/29/2023 · Oregon · 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 : causes phytophotodermatitis.	Up to 6½' (2 m) in height. Poisonous : 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

Plants: 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. 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.

Leaves: Leaves are up to 5' (1.5 m) across, extensively divided into sharp-tipped sections.

Flowers: White flowers form flat-topped compound umbels (flowerheads) up to 30" (76 cm) in diameter.

Fruits: A single plant produces 20,000 oval seeds, each up to ¼" (8.3 mm) long.

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:

Massnrc.org

Luirig.altervista.org

Www.oregon.gov

Wikimedia Commons (Many photos)

Ohioline.osu.edu

Wikipedia

The USDA National Invasive Species Information Center

The USDA Forest Service's Fire Effects Information Database

Www.nrs.fs.fed.us (PDF)

Www.seagrant.sunysb.edu (PDF)