Giant hogweed (Heracleum mantegazzianum )

Invader Type: 
  • Plant

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07/16/12
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Control

Mechanical Control: 

CAUTION: The sap from this plant is dangerous. If it gets on your skin and you are exposed to the sun, it can cause severe burns.

Always wear thick gloves and long pants and shirts.

Manual treatment can be moderately to highly effective for giant hogweed

Giant hogweed leafs out very early compared to most native vegetation, thus making it easy to detect. It is beneficial to manually remove this plant before it begins flowering later in the growing season

Hand Pulling/Digging

  • Pull entire plant by the base of the stem or dig roots with a shovel
  • Be sure to remove entire root system
  • Dry or burn all vegetation (most importantly roots) or collect vegetation and dispose of in a landfill

Mowing/cutting

  • Cut at least 1 time before seeds appear (until July)
  • Repeat for 3-5 years
Chemical Control: 

Active ingredients commonly used in herbicides: Glyphosate or triclopyr

If foliar spraying only:

  • Foliar spray later in the summer (June-mid July)
  • Spray leaf surfaces with low volume backpack sprayer, or high volume mist blower

Low Volume Backpack Sprayer

  • Herbicides (active ingredient): glyphosate or triclopyr with surfactant
  • Used to giant hogweed plants and minimize drift to desirable species

Photos

Photos: 

Description

Identification: 

Giant hogweed is a tall (up to 15-20 ft. [4.6-6.1 m]), herbaceous, biennial plant that invades disturbed areas across both the Northeast and Pacific Northwestern United States. Giant hogweed is designated as a Federal Noxious Weed, because it produces sap that causes skin sensitivity to UV radiation and leads to blistering and severe burns. The large stem is hollow and usually marked with purple blotches. The leaves are deeply lobed, sharply pointed, and up to 5 ft. (1.5 m) wide. Flowering occurs in late spring to early summer. The white flowers are on a large umbrella-shaped head at that can be up to 2.5 ft. (0.8 m) in diameter. Giant hogweed can invade a variety of habitats but prefers moist, disturbed soils such as riverbanks, ditches and railroad right-of-ways. (source: www.invasive.org).

New York State has an excellent identification summary, including comparisons to native plants including cow parsnip.

Check out this video on Giant Hogweed

Reproductive Strategy / Lifecycle: 

Giant hogweed sprouts in early spring and flowers early July. This perennial plant dies back after flowering, leaving tall dead stalks. It forms perenating buds which lie dormant through winter until the next growing season. It reproduces by seed dispersal only, not vegetatively. Each flower head contains approximately 1500 seeds, which can remain viable for up to ten years. 

Dispersal: 

Seeds are dispersed primarily by wind, water, and human and animal activity. It is commonly spread along river banks, where it causes erosion and is swept downstream.

Habitat: 
Giant hogweed is found along roads, forest edges, waterways, and in vacant or disturbed areas. It prefers semi-shade conditions and rich, moist soils.
History: 
Giant hogweed is native to Europe and Asia. It was first introduced into the United States in 1917 for ornamental purposes. source: www.invasive.org
References: 

Photos: Donna Ellis; Les Merhoff; Denholm, NJ Dept of Ag;