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Giant Hogweed:
perennial or biennial; also known as giant cow parsnip. Stable into
Growing Zone 3.
Family: Parsley or
carrot family (Apiaceae or Umbelliferae)
Flower: White or
rarely pinkish; occurs as a compound umbel up to 1 m across under
ideal conditions; those observed on Manitoulin Island were about 0.5
m across; the umbel consists of 30 to 50 branches; each branch ends
in a simple umbel with approximately 30 to 40 flowers; each umbel has
a flat bottom and gently rounded top; flower petals are up to 12 mm
long; June to August.
Leaves: Leaves are
very large, up to 1m across; compound with 3 large deeply cut
leaflets; each leaflet has deep irregular lobes; coarse, sharp teeth
on all margins; leaves are attached to the stem by a petiole.
Stem: The flower
stems are enormous - standing up to up to 5 m tall and up to 10 cm in
diameter under ideal conditions; the plants observed on Manitoulin
Island were about 2 m tall and 3 cm in diameter (as best I could
guess!); stems are hollow except at the nodes; stems and petioles
have an obvious reddish-purple streaks and specks and may be nearly
solid purple near the base; lower stem may be very rough with
pointed, irregularly-spaced bumps.
Seed: Seed remains
viable for 7 years; hence, an eradication program must be sustained
for 7 years!!! Plant produces 1,500 to 100,000 seeds that are
flattened, up to 1 cm long, oval, have a broadly rounded base, and
have broad marginal ridges
Habit: Forms
rosettes up to 1 m tall during the first year; in the second year,
produces flower stem and very large rosette of huge leaves; produces
flower umbels in the third year.
Height: Tall - up
to 5 m under ideal conditions.
Habitat:
Introduced from Europe and has grows along roadsides, steam banks and
waste areas.
Interest: Giant
Hogweed flowering only once in its lifetime. It reproduces only by
seed. The watery, clear sap
causes severe dermatitis in most people when exposed to Sunlight. The
sap contains photosensitizing compounds (furanocoumarins), which are
activated on humans when exposed to Sunlight. Avoid contact!
Effects can last for months and skin can remain sensitive to UV light
for years (see references below - this summary from weedinfo.ca).
Location: Gore Bay
golf club, Manitoulin Island
Date: July 11, 2010 |
