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SEASONAL IDENTIFICATION
GIANT HOGWEED (Heracleum mantegazzianum)
SPRING
SUMMER
SUMMER
SPRING
-
SUMMER
SUMMER
FALL
-
WINTER
Young plants are identified by the leaf only. Rosettes have
large broad leaves with jagged or pointed lobes generally
in groups of three. Seedlings usually only have one
symmetrical leaf with a toothed edge that is wider than long.
The white flower heads at the ends of branches are
composed of many small white flowers that point upwards
and are flat topped or umbrella shaped.
Colonies are easily recognized by their large, white flower
heads, large broad, jagged leaves, and thick hollow stems
covered in hairs and purple spots.
Thick, hollow stems are covered with hairs and have variable
purple blotches that develop vertical ridges that become
more prominent later in the season.
The central flower at the top of the main branch is usually
first to develop seeds. Seeds are flat, round, green disks
covered in hairs.
Giant hogweed is typically dead by fall. Dead giant
hogweed can be seen standing with stout, hollow stems
and seed heads still intact. This weed skeleton is taller
than most other Ohio herbaceous weeds.
