Heracleum mantegazzianum (Giant Hogweed)

Plate 1 figs. a–h

Heracleum mantegazzianum, photographed by Marina E. — fig. a Marina E., CC BY 4.0 / 2022-06-08 / obs. 205478217

Heracleum mantegazzianum, photographed by Charles Joynson — fig. b Charles Joynson, CC0 1.0 / obs. 202977712

Heracleum mantegazzianum, photographed by Rob Wallace — fig. c Rob Wallace, CC0 1.0 / obs. 200339577

Heracleum mantegazzianum, photographed by Hannes — fig. f Hannes, CC BY 4.0 / obs. 197484558

Heracleum mantegazzianum, photographed by Lukas Large — fig. g Lukas Large, CC BY 4.0 / obs. 193691339

Heracleum mantegazzianum, photographed by Rachel Webster — fig. h Rachel Webster, CC0 1.0 / obs. 194244042

Every figure is a research-grade observation under CC0, CC BY or CC BY-SA, rehosted with the photographer’s name, the licence and the observation it came from. Photographs under a NonCommercial licence are excluded from this site and are never stored, which costs us a great many pictures and is not negotiable.

Flowering n = 346 observations

139

132

Flowering observations of Heracleum mantegazzianum by month
Month	Observations
Jan	12
Feb	3
Mar	0
Apr	2
May	8
Jun	139
Jul	132
Aug	7
Sep	5
Oct	1
Nov	6
Dec	31

Peak flowering in Jun, from 346 community-annotated observations worldwide. This is a global aggregate, not a forecast for your garden: the same species flowers on different dates in different hemispheres, and citizen-science records cluster near cities, at weekends, and in spring. Where a species has fewer than 30 annotated records we do not draw this chart at all.

Also published as 4 synonyms

A synonym is not an error. It is a record of botanists disagreeing, in print, about where this plant belongs. Each of these was somebody’s considered answer.

Heracleum circassicum Manden.
Heracleum grossheimii Manden.
Heracleum montegazzianum Sommier & Levier
Pastinaca mantegaziana Koso-Pol.

Sourcesevery claim on this page

World Flora Online Plant List. accepted name, authority, classification. CC0. Retrieved 2026-07-12.
iNaturalist. photographs and flowering annotations, CC0 / CC BY / CC BY-SA only. per photograph. Retrieved 2026-06-27.

We publish what we can source and we say so when we cannot. This page has no care advice, no toxicity claim and no native range, because we do not yet have those from a source we can cite.