Download Fighting Giant Hogweed

Fighting Giant Hogweed
A RETROSPECTIVE OF KING COUNTY’S EFFORTS
FROM 1996 TO 2014
Karen Peterson, Maria Winkler, Sasha Shaw
King County Noxious Weed Control Program
Giant hogweed
Heracleum mantegazzianum
• Is a very large, herbaceous plant in the
Apiaceae or parsley family
• It comes from the western Caucasus
Mountains (Russia, Georgia, Azerbaijan)
• It is considered noxious in several European
countries
• It is listed as a Class A noxious weed here
because of its invasiveness, and health
hazards
Native range
How did it get here?
• Brought over as an ornamental
– Used as a “tropical looking” hardy plant in the gorilla
exhibit at Woodland Park Zoo. Added bonus: the
gorillas wouldn’t eat it. (it’s since been removed)
– Some homeowners in Seattle area took seed from
hogweed in the Arboretum.
• Imported from the middle east as golpar, a spice
used in cooking
• Used as forage until they realized it made the
milk and meat taste bad.
How to identify hogweed
15-20 feet tall at maturity
Red blotched stems, up to 6” in
diameter
Giant Hogweed ID
Extremely large jagged leaves
Raised, red blotches with hairs
Leaves from seedlings to adult
As they get older they get larger and
more divided
Inflorescences can be up to 2.5’ across
• Terminal flowers are those at the
top on the main stem
• Most of those in the terminal are
perfect, ie both male and female
• The umbels on lower and farther
away umbels have perfect or just
male flowers
• The higher order (farther from
terminal) have more male flowers
• If there are both, the male
flowers are located in the center
• First signs of flowering
begin in early May
• It usually takes an average
of 44 days from blooming to
seed set
• Flowers can be self fertile so
there is a high rate of viable
seeds per plant; 10-20,000
Good Guy Look Alike: Native Cow Parsnip
dnr.wi.gov/invasives
upload.wikimedia.org
extension.unh.edu
Seedling in with buttercup and other
plants
What makes hogweed such a
problem?
•
•
•
•
•
•
•
Each plant produces 10,000-20,000
viable seeds
The seedlings germinate early
Plants grow quickly early on,
beating their competition to the
sunlight with their large leaves
It can regenerate quickly if cut back
down to ground level, even when in
seed set
It doesn’t have any specialized
predators
People are reluctant to control it
because they are afraid of it
Sap causes burns, blistering,
blindness
But….
• It is monocarpic, it dies
after it blooms
• The seed bank only lasts 3-5
years
• Most of the seeds
germinate in the first year
What makes hogweed so scary?
Most individuals experience
burning, blistering, discoloration
when coming in contact with the
sap.
Sometimes they show an increased
sensitivity to sunlight for years
Contact with the eyes can cause
blindness, temporary or permanent
People are often exposed to sap when
weed whacking or mowing
• Especially without adequate
coverage
• Always wear long pants,
long sleeves, gloves and eye
protection when working
around hogweed
• Hazmat suits not necessary
furanocoumarins
• These are the chemicals in
hogweed evolved as a
defense against predators
• Furanocoumarins are found
mainly in the sap
• They are at their highest
concentration in the seeds
• They are also found in other
members of Apiaceae but
hogweed has some of the
highest amounts
• Furanocoumarins act as a
phototoxin when exposed
to UV light
• Photodermatitis can occur
24-48 hours after contact
with sap
• Wash immediately with cold
water and cover to protect
from light
Introduced to New York in 1917
Hogweed had been present in Seattle
since the early 1950’s
Within 40 years it had spread 7.5 miles
along French Creek on Vancouver
Island
Sites in King County since 1996
• Dormant sites
• Closed sites
• Total hogweed
1413
967
1779
• There were 116 sites found
in 1996
• There were 118 sites with
hogweed on them in 2013
Known populations in King County
2000
Known populations in King County
2013
Sites surveyed in King County by year
1200
1000
800
600
Sites Surveyed
Sites with hogweed
400
200
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
0
New sites with hogweed
New sites
250
200
150
100
50
0
New sites
Area found
90000
80000
70000
60000
50000
40000
Area found
30000
20000
10000
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
0
Hogweed controlled
1200
1000
800
Sites surveyed
600
Sites controlled
400
200
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
0
Where will it grow?
• In its native range, it grew in a wide variety of
habitats with widely ranging temperatures
• Winter temperatures range from -33 F to 61 F
• Summer temperatures from 27 to 95 F
• Average annual rainfall is 34” (very much like
ours)
• Will tolerate salt spray
• It is very adaptable
Once hogweed is established and there is no
control, it will spread very quickly.
Giant Hogweed Control – Use Caution
What doesn’t work
• Even though it is
monocarpic, cutting it back,
even to the ground when
seeds have formed, will still
result in re-blooming and
setting seed in the same
season
• Cutting vegetative plants
will result in regrowth
• Cutting immediately before
or after spraying
• Spraying at too high a
concentration or too low.
Always check the label
• 2-4 d
• Stomping on them
• Leaving cut flower heads on
ground. They will continue
to flower and set seed
Giant Hogweed Control
First, cut off and bag
flower heads and leaves
Next, dig up roots
completely or cut root
at 6” below stem
Or, you can spray
the plants with
herbicide, either
glyphosate or
triclopyr
The key is to control the
roots – don’t be fooled
by small upper growth
Timing
• Spray in spring while still actively growing
• Digging is easier when soil is still moist and
blackberries are low enough to see the
younger plants
Mechanical control
Digging out the entire root
• Best for young plants
Cutting root
• Be sure to cut at least 6”
below stem
• Sometimes soil can pile
around plant, so be sure to
locate the top of the root
Chemical control
• Best products for control are those with
Glyphosate or Triclopyr as an active ingredient
• Best control in spring while plant is still
growing
• Denmark outlawed the use of pesticides on
public property, but an exception was made
for hogweed
Stem Injection
• Injection is also very effective for treating
hogweed (Glyphosate - Roundup Pro or
Aquamaster):
– Inject one leaf stem per plant 12” above
root crown with 5 ml of a 5% solution of
Roundup Pro Concentrate
– Flowering plants: inject main flowering
stem near base, 2-4 ml of 100% glyphosate;
use cavity needle (wall of stem too thick for
regular needle)
Hogweed site in Normandy Park
Before treatment 2013
2014
Biocontrol
• No insect, fungus or disease
has been found that is
specific enough to target
hogweed alone.
• Except grazers like sheep,
cows or goats (if not used
for milk or cheese)
• Horses tend to avoid eating
hogweed
• If using animals to graze,
the best are those with dark
skin and a dense coat.
Otherwise they can be
sensitive to the sap.
• They need to graze several
times a year for several
years (5-10) to achieve
control
Control and Prevention
• Be aggressive
• Monitor
• Recheck sites for
several years
• Educate the public
•
Return of the Giant
Hogweed
Turn and run!
Nothing can stop them,
Around every river and canal their power is growing.
Stamp them out!
We must destroy them,
They infiltrate each city with their thick dark warning odour.
Genesis, 1971
They are invincible,
They seem immune to all our herbicidal battering.
Long ago in the Russian hills,
A Victorian explorer found the regal Hogweed by a marsh,
He captured it and brought it home.
Botanical creature stirs, seeking revenge.
Royal beast did not forget.
He came home to London,
And made a present of the Hogweed to the Royal Gardens at Kew.
Waste no time!
They are approaching.
Hurry now, we must protect ourselves and find some shelter
Strike by night!
They are defenceless.
They all need the sun to photosensitize their venom.
Still they're invincible,
Still they're immune to all our herbicidal battering.
Fashionable country gentlemen had some cultivated wild gardens,
In which they innocently planted the Giant Hogweed throughout the land.
Botanical creature stirs, seeking revenge.
Royal beast did not forget.
Soon they escaped, spreading their seed,
Preparing for an onslaught, threatening the human race.
Mighty Hogweed is avenged.
Human bodies soon will know our anger.
Kill them with your Hogweed hairs
HERACLEUM MANTEGAZZIANI
Giant Hogweed lives
• King County Noxious Weed Control Program
• 206-477-WEED
• www.kingcounty.gov/weeds