[email protected]www.ssisc.info 604-698-8334 Giant hogweed a.k.a giant cow-parsnip (Heracleum mantegazzianum) Identification Principal Distinguishing Features: tall when in flower (2 to 6m), hollow stems 5-10 cm wide with course hairs numerous, small white flowers in a large, flat topped, terminal umbrella like cluster very large, deeply incised “maple leaf-like” leaves to over 1.5 m wide Life cycle: perennial Rooting habit: variable – stout, fleshy tuberous root stalks that form buds each year Main vectors of spread: seed production (up to 50,000 seeds per plant) which are winged for ease of dispersal by wind. Seeds remain viable for 7-15 years. vegetative – plants develop perennial buds that form on the root stalks or the crown Preferred habitat: moist areas such as ditch lines, meadows, thickets, avalanche tracks, streams, roadsides. Prefers partial shade Look-alikes: The most reported look-alike is the common native cow parsnip (Heracleum maximum). It should be noted that cow parsnip possesses similar chemicals to giant hogweed, capable of causing photosensitivity when in contact with skin (to a lesser extent but noteworthy). See following chart for a comparison of diagnostic features. Feature Cow parsnip Giant hogweed Height of flowering stem 1 – 3 m 3 – 10 feet 1.5 –4.5 m 5 – 15 feet In Squamish as seen from 5ft Vancouver Island Lions Bay J. Hallworth FVRD
tall when in flower (2 to 6m), hollow stems 5-10 cm wide with course hairs
numerous, small white flowers in a large, flat topped, terminal umbrella like cluster
very large, deeply incised “maple leaf-like” leaves to over 1.5 m wide
Life cycle: perennial Rooting habit: variable – stout, fleshy tuberous root stalks that form buds each year Main vectors of spread:
seed production (up to 50,000 seeds per plant) which are winged for ease of dispersal by wind. Seeds remain viable for 7-15 years.
vegetative – plants develop perennial buds that form on the root stalks or the crown Preferred habitat: moist areas such as ditch lines, meadows, thickets, avalanche tracks, streams, roadsides. Prefers partial shade Look-alikes: The most reported look-alike is the common native cow parsnip (Heracleum maximum). It should be
noted that cow parsnip possesses similar chemicals to giant hogweed, capable of causing photosensitivity when in
contact with skin (to a lesser extent but noteworthy). See following chart for a comparison of diagnostic features.
Feature Cow parsnip Giant hogweed
Height of flowering stem
1 – 3 m 3 – 10 feet
1.5 –4.5 m 5 – 15 feet
In Squamish as seen from 5ft Vancouver Island Lions Bay
Other look-alikes include similar plants in the carrot family with white umbels of flowers such as poison hemlock (Conium maculatum) and wild carrot (Daucus carota), which are generally much smaller and less robust than giant hogweed. Another look-alike when looking at leaves alone is the horticultural giant rhubarb (Gunnera manicata).
Current know distribution & Priority in the Sea to Sky Relatively small sites are in Lions Bay, Brittania Beach and Squamish – Eradicate (species is here in small amounts and
elimination is the goal).
Reasons for concern Safety: hairs on stems and leaves contain POISONOUS SAP which exude a clear, watery sap sensitizing skin to ultraviolet radiation; resulting in severe burns, blistering and painful dermatitis (forming 24 to 48 hours after contact). Avoid contact with eyes – may cause temporary or permanent blindness.
Ecological: rapidly occupies and forms a dense canopy in riparian areas out-competing native species and causing stream bank erosion.
Control strategies Plants over 1m in height are not to be removed, handled, cut down or contacted in any way that could lead to exposure of workers to Giant hogweed sap (stems, leaves and stalk). If workers are exposed to the sap see “If exposed to Giant hogweed sap” below. Plants that have flowered are to be dealt with on a case by case basis but it is recommended the plants are left alone until the following spring. When needed, the SSISC will coordinate fencing off plants on public property with adequate signage to ensure that residents do not come in contact with the plant.
The most effective treatment for Giant hogweed is to slice through the taproot at a depth of 10cm (4 inches) with a shovel. Sites should be checked every two weeks through the spring and managed as needed. A site should be managed for 3-5 years to ensure new plants do not sprout. Protocol for Giant hogweed under 1m in height Equipment:
Access to water or portable water source (for cleaning gloves and clothes)
Eyewash station
Hand soap
Sunglasses that block UV light
Long pants and long-sleeved shirt
Sunblock
Goggles
Heavy rubber gloves or other waterproof gloves that can be discarded after use (dishwashing gloves)
Waterproof coveralls or rain gear (pants and jacket with hood)
Rubber boots
Shovels
Loppers **DO NOT USE POWER EQUIPMENT (WEED WHACKERS) TO REMOVE GIANT HOGWEED, SAP CAN SPLASH OUT OF PLANT STEMS AND ONTO THE FACE OR OTHER EXPOSED SKIN Timing:
Removal is ideal between the months of April - May
Do not remove on sunny days especially between the hours of 11am – 3pm
Removal is recommended on overcast days, or at dawn and dusk Gear up:
Apply sunblock to face, hands and wrists.
Put on goggles, waterproof coveralls, rubber gloves and boots Giant hogweed removal, under 1m:
Small plants can be hand pulled
For larger plants the upper portions of plant should be cut back with loppers to allow for easier access to stem and taproot
Using a shovel place the blade approx. 10cm (4 inches) from stem of plant, drive blade into earth and cut through hogweed taproot below the surface of the ground. Stem can then be pulled up and dirt kicked in to fill the hole left from removal
Plants are left in place to rot Gear down: **do not remove goggles until hands are washed with soap and water and any chance of accidental contact between sap and eyes has been removed.
BEFORE REMOVAL, gloves, coveralls and boots should be rinsed with water, paying special attention to gloves and sleeves
Carefully remove gloves, coveralls and boots by turning protective clothing inside out while removing to ensure any portions of clothing that were exposed to hogweed sap will not accidentally come into contact with skin
Wash hands with soap and water
Remove goggles
Disposable coveralls and gloves should be disposed of after use, any non-disposable clothing should be washed carefully with soap and water
Protocol for Giant Hogweed that has flowered Equipment:
(as above for removal under 1m)
Large plastic garbage bags
Scythe on end of long pole Timing, Gear up and Gear down is as above for removal under 1m Giant hogweed removal, flowered:
Ensure no person in the work party will be hit by the plant when it falls down
Using scythe on long pole cut stem of Giant hogweed (best cut in an upward angle)
Cut off flower and bag, flowers can be cut to fit into garbage bags
Remove bagged flowers from site
There is no need to cut taproots of flowered plants, Giant hogweed is a biennial plant and the taproot should die after it has flowered
Giant hogweed flower disposal:
Bags of flowers must be handled with same care as Giant hogweed, sap may have transferred during bagging process so ensure goggles and gloves are worn, follow Gear up and Gear down instructions as above
Bags must be disposed of with garbage, DO NOT PUT IN GREENWASTE If exposed to Giant hogweed sap: Eyes:
Immediately flush with clean water for 1 min
Put on sunglasses and see your doctor Skin:
Immediately wash with cold water and soap
Cover area with long sleeved shirt or pants
Keep area out of sunlight for 48 hours
If darkening of skin occurs see your doctor
Area could be sensitive to sunlight for many years after, be aware of area and cover with sunblock
BC Legislation: Weed Control Act (new addition September 2011)
Origin: Native to Asia, more specifically the western Caucasus
