Giant Hogweed (Heracleum mantegazzianum)

Common names:
Give a thumbs up Giant Hogweed
Give a thumbs up Giant Cow Parsnip

General Plant Information (Edit)
Life cycle: Perennial
Sun Requirements: Full Sun
Full Sun to Partial Shade
Minimum cold hardiness: Zone 3 -40 °C (-40 °F) to -37.2 °C (-35)
Maximum recommended zone: Zone 9b
Plant Height: 6 - 12 feet
Plant Spread: 3 - 5 feet
Leaves: Unusual foliage color
Other: Handling plant may cause skin irritation or allergic reaction, do not touch the plant
Fruit: Showy
Flowers: Showy
Flower Color: White
Bloom Size: Under 1"
Flower Time: Late spring or early summer
Late summer or early fall
Uses: Cut Flower
Will Naturalize
Wildlife Attractant: Bees
Toxicity: Other: Giant hogweed sap contains toxic chemicals that, when they come in contact with the human skin, can cause painful blisters and permanent scarring. If it gets into an eye, it can even cause blindness.
Propagation: Seeds: Provide light
Stratify seeds: 6 weeks if you sow indoors
Suitable for wintersowing
Sow in situ
Start indoors
Can handle transplanting


Photo gallery:

Posted by Bonehead (Planet Earth - Zone 8b) on Mar 26, 2018 4:13 PM

Class A noxious weed in Washington state (relative new-comer, trying to eradicate before it settles in). Forms dense canopies that out-compete natives, and increases erosion along waterways. Dig out, but be cautious. As noted by others, the clear watery sap can sensitize the skin to sunlight, resulting in a blistering long-lived rash.

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Posted by funnynancy on Apr 28, 2014 7:43 AM

I recently saw a post on facebook that this plant is very dangerous. It claims the plant can be deadly and/or cause blindness. It showed men in protective suits removing the plant from gardens. Do you have any information about this?

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Posted by LindaTX8 (Medina Co., TX - Zone 8a) on Jun 18, 2018 1:36 PM

Noticed this article in the news, which led me to look up this scary and harmful invasive plant:

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Discussion Threads about this plant
Thread Title Last Reply Replies
Interesting article on Giant Hogweed by crawgarden Nov 30, 2017 9:26 PM 2
Hogweed or cow parsnip by dukejohn2000 Jul 7, 2017 3:55 PM 2
Unidentified Ditch plant by Bubbeez Jun 15, 2017 11:08 AM 5
These "weeds" are turning into trees, and I'm going to let them! by eturner99 May 1, 2017 7:07 PM 17
Yardening in the Mid-Atlantic by Eric4home Jan 19, 2020 1:23 PM 3,202
Is that a weed or a native? by Bonehead Jun 24, 2013 12:52 PM 47
Wildflowers of Iceland and Greenland, Platanthera hyperborea by Ursula Aug 22, 2011 9:31 AM 18

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