COMMON NAME

Giant hogweed
Giant cow parsnip


FULL SCIENTIFIC NAME

Heracleum mantegazzianum Sommier & Levier


FAMILY NAME COMMON

Carrot family


FAMILY SCIENTIFIC NAME

Heracleum mantegazzianum


IMAGES


Leaf

Habit

inflorescence with fruit

Stem cross-section

Inflorescence

Habit

Close-up of fruits

Close-up of stem

Infructescences

NOMENCLATURE/SYNONYMS

Synonyms: None


DESCRIPTION

Botanical Glossary

Heracleum mantegazzianum is a herbaceous biennial or monocarpic perennial that can grow up to 4.3-5.8 m (15-20 ft.) in height. The stem is hollow and usually blotched with purple. Both the leaf stalks and stem produce pustulate bristles. The stem can be 4.8-9.6 cm (2-4 in.) in diameter. The leaves are ternate or ternate-pinnate with pinnately lobed lateral segments. They can be up to 3 m (9.8 ft.) in breadth. Heracleum mantegazzianum flowers from June-July. The inflorescence has many white florets (with petals about 1 cm) that form a flat-topped umbel. Each inflorescence can have a diameter of up to 0.72 m (2.5 ft.). The fruits are dry and elliptic, measuring 8-11 mm (0.3-0.4 in.) long and 6-8 mm (0.25-0.3 in.) wide. The fruits have brown resin canals that can be up to 1 mm (0.04 in.) in diameter. Page References Bailey 751, Flora Europaea 2:366, Gleason & Cronquist 382, Holmgren 358, Magee & Ahles 785. See reference section below for full citations.


SIMILAR SPECIES

Heracleum maximum Bartr. (synonym: H. lanatum Michx.) (common cow parsnip)
Pastinaca sativa L. (wild parsnip)
Angelica atropurpurea L. (purple stem angelica)
Phytolacca americana L. (pokeweed)
Lactuca biennis (Moench) Fern. (blue lettuce) Click here for a link to the Giant Hogweed comparison table Other species not shown in table:
Cicuta maculata L. (spotted water hemlock) Picture of C. maculata
Conium maculatum L. (poison hemlock) Picture of C. maculatum


REPRODUCTIVE/DISPERSAL MECHANISMS

Heracleum maximum is often found along stream banks, and the seeds can be transported downstream by water.


DISTRIBUTION

Heracleum mantegazzianum is a native of the Caucasus Mountains and southwest Asia. It was introduced as a garden plant in the United States, Europe, Canada and the United Kingdom. It was reported in Canada in southern Ontario around 1950. In the United States it is has been reported from Washington, Oregon, Illinois, Michigan, New York and Pennsylvania. In New England it has been identified in Maine, Vermont, Massachusetts and Connecticut.


HISTORY OF INTRODUCTION IN NEW ENGLAND

Heracleum mantegazzianum was introduced as early as 1917 as a garden curiosity, and most likely reached New England through cultivation in gardens.


HABITATS IN NEW ENGLAND

Edge, Floodplain Forest, River or Stream, Roadside, Vacant Lot, Yard or Garden

Heracleum mantegazzianum is present along roadsides, in vacant lots and along streams and rivers. It prefers rich, moist soil, in semi-shade conditions.


THREATS

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 sever burns. Caution should be taken when handling this weed. Removing it manually becomes very difficult because of the danger caused by its sap.


DOCUMENTATION NEEDS

Documentation required: Specific photograph or mounted snippet showing the inflorescence with scale so as to ascertain the size.
Best time for documentation: Summer


ADDITIONAL INFORMATION

Integrated Taxonomic Information System
Taxonomic information about the species

The PLANTS database
General information and a map

USDA, ARS, National Genetic Resources Program
General and taxonomic information

Federal Noxious Weed Inspection Guide
General information including natural history


REFERENCES

Bailey, L. H. 1949. Manual of Cultivated Plants. Macmillan, New York.

Caffrey, J.M. 1999. Phenology and long-term control of Heracleum mantegazzianum. Hydrobiologia 415, 223-228.

Dodd, F.S., L.C. de Waal, P.M. Wade and G.E.D. Tiley. 1994. Control and management of Heracleum mantegazzianum (giant hogweed). In: de Waal, L.C. et al. (eds) Ecology and management of invasive riverside plants. John Wiley & Sons, Chichester, pp. 111-126.

Gleason, H.A. and A.C. Cronquist.  1991.  Manual of Vascular Plants of the Northeastern United States and Adjacent Canada. 2nd ed.  New York Botanical Garden, Bronx, New York.

Holmgren, N.H. 1998. Illustrated Companion to Gleason and Cronquist's Manual.  New York Botanical Garden, Bronx, New York.

Magee, D.W and H.E. Ahles. 1999.  Flora of the Northeast. University of Massachusetts Press, Amherst.

Morton, J.K. 1978. Distribution of giant cow parsnip (Heracleum mantegazzianum> ) in Canada. Canadian Field Naturalist. 92(2):182-185.

Pysek, P. and A. Pysek. 1995. Invasion by Heracleum mantegazzianum in different habitats in the Czech Republic. Journal of Vegetation Science. 6:711-718.

Tutin, T.G., V.H. Heywood, N.A. Burges, D.M. Moore, D.H. Valentine, S.M. Walters, D.A. Webb, Eds. 1968.  Flora Europaea, Volume 2.  Cambridge University Press, London, UK.

USDA, NRCS.  2001.  The PLANTS Database, Version 3.1. (http://plants.usda.gov).  National Plant Data Center, Baton Rouge, LA 70874-4490 USA.