Giant hogweed (Heracleum mantegazzianum )
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
- 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
- Cut at least 1 time before seeds appear (until July)
- Repeat for 3-5 years
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
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).
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.
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.
Photos: Donna Ellis; Les Merhoff; Denholm, NJ Dept of Ag;