Photo by Melody

PlantFiles: Giant Hogweed
Heracleum mantegazzianum

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Family: Apiaceae (ay-pee-AY-see-ee) (Info)
Genus: Heracleum (hair-uh-KLEE-um) (Info)
Species: mantegazzianum (man-tee-gaz-zee-AH-num) (Info)

Synonym:Heracleum laciniatum
Synonym:Heracleum persicum
Synonym:Heracleum pubescens

2 members have or want this plant for trade.

Category:
Biennials

Height:
15-20 ft. (4.7-6 m)

Spacing:
36-48 in. (90-120 cm)

Hardiness:
USDA Zone 3a: to -39.9 C (-40 F)
USDA Zone 3b: to -37.2 C (-35 F)
USDA Zone 4a: to -34.4 C (-30 F)
USDA Zone 4b: to -31.6 C (-25 F)
USDA Zone 5a: to -28.8 C (-20 F)
USDA Zone 5b: to -26.1 C (-15 F)
USDA Zone 6a: to -23.3 C (-10 F)
USDA Zone 6b: to -20.5 C (-5 F)
USDA Zone 7a: to -17.7 C (0 F)
USDA Zone 7b: to -14.9 C (5 F)
USDA Zone 8a: to -12.2 C (10 F)
USDA Zone 8b: to -9.4 C (15 F)
USDA Zone 9a: to -6.6 C (20 F)
USDA Zone 9b: to -3.8 C (25 F)

Sun Exposure:
Sun to Partial Shade

Danger:
All parts of plant are poisonous if ingested
Handling plant may cause skin irritation or allergic reaction

Bloom Color:
White/Near White

Bloom Time:
Mid Spring
Late Spring/Early Summer
Mid Summer

Foliage:
Bronze-Green
Veined

Other details:
Average Water Needs; Water regularly; do not overwater
May be a noxious weed or invasive

Soil pH requirements:
Unknown - Tell us

Patent Information:
Unknown - Tell us

Propagation Methods:
From seed; direct sow outdoors in fall

Seed Collecting:
Unknown - Tell us

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Thumbnail #1 of Heracleum mantegazzianum by poppysue

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There are a total of 31 photos.
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Profile:

2 positives
3 neutrals
5 negatives

Gardeners' Notes:

RatingAuthorContent
Negative coriaceous On Feb 3, 2014, coriaceous from ROSLINDALE, MA wrote:

Skin contact with the juice followed by exposure to the sun can cause permanent scarring. Sap in the eyes can cause blindness. Just brushing against the hairs can cause dermatitis. There are also many documented reports of injuries to animals.

This plant isn't just a hazard to people and animals, but also an invasive threat to natural habitat. 13 states have independently banned this as a noxious weed, and the United States federal government has made its cultivation illegal throughout the US. The US has taken the extra step and made it mandatory to report any infestation to the USDA/APHIS.

Heracleum persicum is a different species and not a synonym, though it too is a threat to natural habitat in a wide range of climates, and Norway has a program to fight its spread.

Neutral nicholtammy On Jul 23, 2010, nicholtammy from Huntsville
Canada wrote:

My friend had this in her garden we prized it until we found out what it was, the ministry of natural resourses is removing it soon we were told not to remove it ourselves because of the dangers of the sap

Positive giftgas On Mar 7, 2009, giftgas from Everson, WA (Zone 7b) wrote:

I love this plant...it doesn't spread, grows slowly, and looks alien. Thus being said - I grow this plant on purpose, and I enjoy it. Most everything you hear about this plant is a lie, except for the phototoxicity, and even that is greatly exaggerated. Poison ivy is many times more dangerous than this plant.

If people are having problems with this plant, it's because they lack the ability to talk to their children about the various dangers of the world. While it might be difficult to teach your children about how to identify poison ivy, Giant Hogweed looks like it fell from space...like something from another world; once you've seen it, you'll never forget it, and neither will your children.

If you grow monkshood/wolfsbane, castor beans, oleander, fox glove, rosary peas, etc, and you haven't grown Giant Hogweed because its "dangerous"...then there is something amiss in the world. I could name 1000 plants that will kill a human in seconds, and Giant Hogweed is at the bottom of that list, and it's not even invasive.

While this plant may be on the Federal Weed list, perhaps it's because 6 of the most important new medical compounds (drugs) in the world are being synthesized from this plant.

Neutral DMersh On Jul 7, 2007, DMersh from Perth
United Kingdom (Zone 7b) wrote:

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.

Neutral frostweed On Dec 27, 2006, frostweed from Josephine, Arlington, TX (Zone 8a) wrote:

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

Negative caron On Nov 25, 2004, caron from Woodland Park, CO (Zone 4b) wrote:

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).


Positive melangemerchant On Aug 5, 2004, melangemerchant from Adelaide
Australia (Zone 10a) wrote:

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.

Negative TropicofVermo On Aug 13, 2002, TropicofVermo wrote:

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 http://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.

Negative philomel On Jun 8, 2002, philomel from Castelnau RB Pyrenes
France (Zone 8a) wrote:

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.

Negative mystic On Aug 18, 2001, mystic from Ewing, KY (Zone 6a) wrote:

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.

Regional...

This plant has been said to grow in the following regions:

,
Amston, Connecticut
Middleport, New York
Nunda, New York
Webster, New York



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