giant hogweed
Heracleum mantegazzianum Sommier & Levier


Overview


Appearance
Heracleum mantegazzianum is a herbaceous biennial or monocarpic perennial that can grow up to 15-20 ft. (4.3-5.8 m) in height. The stem is hollow and usually blotched with purple. Both the leaf stalks and stem produce pustulate bristles. The stem can be 2-4 in. (4.8-9.6 cm) in diameter.
Foliage
The leaves are ternate or ternate-pinnate with pinnately lobed lateral segments. They can be up to 9.8 ft. (3 m) in breadth.
Flowers
Heracleum mantegazzianum flowers from June-July. The inflorescence has many white florets (with petals about 0.4 in. [1 cm]) that form a flat-topped umbel. Each inflorescence can have a diameter of up to 2.5 ft. (0.72 m).
Fruit
The fruits are dry and elliptic, measuring 0.3-0.4 in. (8-11 mm) long and 0.25-0.3 in. (6-8 mm) wide. The fruits have brown resin canals that can be up to 0.04 in. (1 mm) in diameter.
Ecological Threat
Heracleum mantegazzianum can outcompete species for habitat, especially in riparian zones, and it may cause increased soil erosion. This plant is on the federal noxious weed list because of its poisonous sap. This sap makes skin very sensitive to UV radiation, causing blistering and severe burns. Caution should be taken when handling this weed. Removing it manually becomes very difficult because of the danger caused by its sap.

Resources


Selected Images



Maps



EDDMapS Distribution

EDDMapS Distribution - This map is incomplete and is based only on current site and county level reports made by experts, herbaria, and literature. For more information, visit www.eddmaps.org

State Regulated List

State Regulated List - This map identifies those states that list this species on their regulated list. For more information, visit Invasive.org

Taxonomic Rank


Kingdom: Plantae
Phylum: Magnoliophyta
Class: Magnoliopsida
Subclass: Rosidae
Order: Apiales
Family: Apiaceae
Genus: Heracleum
Subject: Heracleum mantegazzianum Sommier & Levier

Categories


Plants - Forbs/Herbs