HomeMy WebLinkAboutGiant Hogweed.pdf
Giant Hogweed Young stages Full bloom – Noxious stage
Maple Ridge Noxious Weeds Program
Giant Hogweed
(Heracleum mantegazzianum)
Designation: Provincially Noxious
History:
Introduced from Asia as an ornamental
garden plant in Europe, United Kingdom,
USA, and Canada. It has now naturalized
in many of these places, especially along
waterways.
How to Identify:
Size: Not best way to identify plant. Plants
in final year of growth are very large, up
to 5 m tall.
Flowers: White flowers in umbrella‐
shaped heads up to 1.5 m in diameter;
may start blooming in June.
Leaves: Large leaves with coarse, jagged
edges like a serrated knife, cut into three
large segments with stiff hairs on
underside of leaves.
Stem: Hollow, reddish‐purple blotches,
streaks, or spots, and stiff bristly hairs.
Location: Riparian areas, roadsides,
agricultural land, disturbed areas.
Mistaken Identity: Often confused with
native cow parsnip which is much smaller
to 2.5 m tall. Cow parsnip leaves are more
palmate without stiff underside hairs.
Queen Anne’s Lace and Palmate Coltsfoot
are related but much smaller.
Danger / Impact
Very dangerous to human health. Sap
causes extreme skin dermatitis in the
presence of sunlight. Contact can lead to
welts, rashes, blistering, and scarring. If
sap gets into the eyes, it can lead to
temporary or permanent blindness. Giant
Hogweed is toxic at any growth stage.
Displaces native vegetation and reduces
suitable habitat for wildlife.
Produces copious seeds (100,000 seeds
per plant).
Shallow root can allow erosion on slopes.
Management:
Due to health risk, best removed by a professional. Where mechanical
treatment is not feasible (e.g. inaccessible roots, very large number of
plants) herbicide treatment by a certified professional may be
necessary. If attempting removal yourself, cut the root crown 8 – 10 cm
below soil with a sharp blade.
Chemical treatment is best completed using a glyphosate product.
Aminopyralid (Milestone) is not a suitable treatment for mature Giant
Hogweed.
Caution: Wear protective water proof clothing, gloves and safety
goggles. Refer to WorkSafe BC Protocol at
http://www.worksafebc.com/publications/health_and_safety/bulleti
ns/toxic_plants/assets/pdf/tp0602.pdf Beware of indirect exposure to
sap rom contaminated tools, gear, gloves and garbage bags. Use
extreme caution when removing contaminated gear.
Bag plant and seed heads in double garbage bag to avoid on site spread
and to avoid contact during handling/transport.
Timing: March to October (before first frost when plant goes dormant
for winter).
Disposal: Do not compost. Do not put in green waste container. Dispose
in landfill. Cut material can be left on site to decompose if there is no
risk of anyone coming into contact with plant for three weeks AND
there are no seeds. Seed heads must be cut off and disposed of in
landfill regardless of treatment method (chemical or mechanical).
Follow‐up: Monitor every two weeks until no re‐growth or new
seedlings appear (seed bank can last 10 years though germination is
most likely for two‐three years after treatment begins). Follow up for
new germinates can be done mechanically by cultivating soil using a
rake or blade or chemically using a glyphosate product.
Restoration and Planting Alternatives:
Red elderberry (Sambucus racemosa)
Vine maple (Acer circinatum)
Salmonberry 9 (Rubus spectabilis)
And other native plants
Cow Parsnip – Native Species easily mistaken for Hogweed
Distribution in DMR:
Small groups of plants found in only a few areas;
a weed for rapid response and eradication.
Who Do you Call?
1) REPORT PROHIBITED WEEDS – Report‐A‐Weed: www.reportaweedbc.ca 1‐888‐WEEDSBC
2) DMR: 604‐467‐7363 – AND SEE: http://www.mapleridge.ca/714/Invasive‐Plant‐Species
Information and photos:
http://www.bcinvasives.ca/images/stories/plants/gianthogweed/gianthogweed01.jpg
http://www.iscmv.ca/species‐profiles/giant‐hogweed
http://westvancouver.ca/sites/default/files/dwv/assets/home‐building‐property/docs/pets‐wildlife‐environment/Invasive‐Plants/APPENDIX_A_‐
_JANUARY_28__2014_DRAFT.pdf