Invasive Plants:the Increasing Threat to Habitat & Biodiversity
Tonight’s Outline
• Weeds & Lists
• Impacts
• Resources
• Specific Weeds & Management
• Manual, mechanical, chemical
Chemical Option: Herbicides
• Know your target weed first
• Read label before you purchase
• Follow the label (it’s Federal Law)
• Timing is crucial for success
• Using the labeled rate is crucial too– Follow rate recommendations
– MORE IS NOT BETTER • MORE can actually make the treatment LESS effective
• Rates in presentation expressed as %– Ex: 128 oz/gal (water)
128 x .01 (1%) = 1.28
– 1% rate =1.28 oz herbicide/gal of water
– 2% rate (128 x .02) =2.56 oz herbicide/gal of water
– 5% rate (128 x .05) = 6.4 oz herbicide/gal of water
(1 oz = 2 Tablespoons)
• Washington State Weed Law (RCW 17.10)
• Washington State Noxious Weed List
(WAC 16-750)
• Requires the landowner to control or manage listed noxious weeds
• County weed coordinator ensures that landowners control their weeds
*also a legal term in Washington
Noxious (nok´shəs). adj. 1.Harmful or
injurious to health or physical well-being*
The 3 Classes of Noxious Weeds
Class A Noxious Weeds are limited in their
distribution throughout Washington State,
High Priority.
Goal – Eradication/Prevention of new
Class B Noxious Weeds are limited in their
distribution to parts of Washington State
Goal – Containment/Prevention of seedfall.
Can be Designated by the state for control in
specified counties or regions
Class C Noxious Weeds are widespread in
Washington State
Goal – Containment as required by county
sometimes through special interests such as
the agriculture industry
Giant
Hogweed
Himalayan
Blackberry
Purple
Loosestrife
Washington’s Noxious Weed Lists
• 2018 Washington State Noxious Weed List –
established plants which need management or
eradication in Washington State (chosen through
annual review and public hearing)
153 plant species
2018 Whatcom County Noxious Weed List
Selected annually through public hearing process
123 plant species
• Washington State Monitor List (Non-Regulatory) – “suspect”
weeds for information gathering
43 plant species
• Washington’s Prohibited Plants List – plants/plant parts cannot be
bought, sold or transported
86 plant species
THESE LISTS ALL INCLUDE DIFFERENT PLANT SPECIES
Over half of the listed noxious
weeds in Washington State
were first introduced as
garden ornamentals
What is a Weed?
• A plant out of
place
• “...a plant whose
virtues have not
yet been
discovered.”
-Ralph Waldo Emerson
Competitive Abilities
• abundant reproduction
• means of seed dispersal
• Rapid growth from seed,
rhizomes, stolons etc.
• seed longevity
• adaptability to wide range
of conditions
• allelopathic
• thrive in disturbed soil
Weed Life CyclesAnnual Biennial Perennial
1-year life cycle 2-year life cycle Multiple year life cycle
Easiest to work with A little more difficult Most difficult
Spread by seed (prolific) Spread by seed Spread by seed, roots, fragments, tubers, etc.
Summer or winter seeding Rosette plant 1st year
Flower/seeds 2nd year
Can behave like perennial
Bittercress BindweedBull Thistle
Identification
• The most important first step
Bull Thistle Canada Thistle
Which Thistle is Which?
Canada ThistleCirsium arvense
Rhizomes (creeping roots)
Bull ThistleCirsium vulgare
Tap Rooted
Himalayan BlackberryRubus armeniacus
Class C
• Native to Western Europe
• Reproduces by seed and
by canes rooting in the
ground
• Very aggressive growth
• Hand-grubbing – get all of the
roots
• Mowing repeatedly
• Goats
– They can mow plants back so
access to the roots is easier for
digging
• Herbicide
– Foliar Spray: 1-1.5%
glyphosate in the fall (1.3-1.9 oz concentrate /gal water)
Management Options
Disposal Options:
• Move to impervious areas to dry out and then haul away
• Bag and haul
• Do not compostFlorafinder.com
• Produces up to 12,000 seeds per
plant per year
• Seeds can be flung 10-15 feet by
ripe exploding pods
• Seeds can lie dormant from 5 - 30
years
• Scotch broom pollen is not a likely
source of common allergies
Scotch BroomCytisus scoparius
Management Options
• Weed Wrench™/ Extractigator™• soil disturbance can sometimes
cause dormant seeds to germinate
• Cut stem and girdle
good for places where erosion is
a concern
•Herbicide–Triclopyr – cut stump treatment
– Glyphosate – 1.5-2% in the spring(1.9-2.5 oz concentrate/gal water)
• 13-petaled yellow flowers
• Leaves have wavy margins
• spreads by seed (wind)
• contains alkaloids toxic to
livestock
Tansy Ragwort
Senecio jacobaea
Class B
Management Options
• Hand-pulling
– at bolting stage
– can clip heads if blooming and bag
up
– DO NOT leave blooming/pulled
plants to dry out in the open
• Herbicide– 2,4-D (many brand names)
– 2,4-D/Triclopyr (Crossbow, etc.)
– 2,4-D/Dicamba (WeedMaster, etc)
• spring or fall timing is best• follow label rates
• spray to wet
• Mowing not recommended
Common Tansy
St. Johnswort
Not to be confused
with...
• From residences, moving into natural areas
• spreads by seed (birds) and creeping roots
• Adds enormous weight loads to trees once established, increasing tree/property damage
• Also crowds out understory shrubs/plants
• Plants mature and produce seed in 8-9 years
• Attracts rats and rot
English/Atlantic/Irish IvyHedera sp.
Class C
mature
seed
1st year seedling
Management Options
•Hand-pulling, grubbing, mowing
regularly, rolling for ground level
sites
• Mulching – 8 inches of material
• Cutting for trees
• HerbicideGlyphosate
– Foliar: 2-4%, surfactant is important
– leaf treatment to open waxy surface
– Basal treatment: spray base of plant
with 33% solution
– Cut Stem: cut stem and treat
immediately with herbicide
Cutting at Ground and Shoulder Level
Bohemian KnotweedPolygonum x bohemicumClass B/Prohibited Plant List
• Hybrid of Japanese and
Giant Knotweed
• Hollow jointed stem
• White flowers in late
summer (bees love it)
• Extensive, fleshy roots
• Spreads primarily through
root/plant fragments, but
also by seed
• Can grow through asphalt
and survive in marine
intertidal areas
• Leaf litter from knotweed very low in nitrogen
• Alters food web in riparian areas by decreasing native
leaf litter by as much as 70%• Foliar/Bending (large
monocultures)
– 3-5% glyphosate
– And/Or .05 -1.0% imazapyr
– Optional June/July bending
– August thru October foliar
applications
• Injection (isolated patches)
– 5 ml of 100% glyphosate per
stem
– Removal by digging
recommended only for patches
< 1 meter in diameter.
Management Options
English HollyIlex aquifolium
Monitor List (non-regulatory)
• Toxic to humans
• Invades native forest
• Water glutton
• Extremely difficult to manage
when it matures (to 50 feet tall)
Management Options
• Hand Pulling– Remove small seedlings
– Repeated cutting of larger
plants for suppression
• Herbicide– Glyphosate, Imazapyr,
Triclopyr
– Cut stump
– Frill cut
– Follow label instructions for rate
Yellow ArchangelLamiastrum galeobdolon
Class B-Designate/Prohibited Plant List
• native to Europe
• introduced as a
garden ornamental
and groundcover
• very invasive,
spreading both by
seed and by
runners
• often spread by
yard waste dumping
• now banned from
sale in Washington
Management Options
• Hand Pulling
– remove all plant parts and bag
for disposal
– No composting
– Can mulch to help hand pulling
• Regular and careful mowing
• Sheet mulching
– layers of newspaper/cardboard
with 3-4 inches of mulch on top
• Herbicide–Triclopyr, Metsulfuron (Escort ™), Imazapyr
(Polaris™, Habitat™)
– select carefully and follow label rates
Spurge LaurelDaphne laureola
Class B
• Evergreen shrub about 4 fttall
• Looks like a rhododendron but without showy flowers
• Flowers are very small and green
• Black, shiny berries
• All parts of the plant are poisonous and can cause severe skin and eye irritation
Management Options
• Hand Pulling
– Wear protective clothing and eye
protection
– No composting pulled plants
– Weed Wrench/Extractigator
– Remove small seedlings by hand
(waiting until they’re bigger requires tools
for removal)
• HerbicideTriclopyr
– Cut stump
– follow label
instructions for
rates
- - ground level - -
Herb RobertGeranium robertianum
Class B
• aka “Stinky Bob”
• Looks like an innocent
wildflower
• Pink flowers
• Musky odor
• Produces prolific amounts of
exploding seed
• Allelopathic
Dovesfoot Shiny
Shiny GeraniumGeranium lucidum
Class B-Designate/Prohibited Plant List
• Looks like dovesfoot geranium,
a common garden weed
• Shiny leaf
• Pink flower
• Unusual ridged seed pod
Shiny Dovesfoot Stinky Bob
Garlic MustardAlliaria petiolata
Class A/Prohibited Plant List
• displaces understory plants
• smells like garlic and mustard
• allelopathic
• looks like native fringe cup
and/or nettles before it bolts
• Found in most Western WA
counties
• Stinky Bob– Hand pulling before flowering
– Glyphosate spot spraying at 2% in
spring
• Shiny geranium– Hand pulling before flowering
– Glyphosate and Imazapyr
recommended but results have been
mixed
• Garlic Mustard– Hand pulling
– must clean off shoes and
equipment before leaving area
– Glyphosate spot spraying at 2% in
spring
Management Options
• Tall woody shrub
• purple to white spike flowers
• prolific seed producer – 3
million/plant
• competes with willow, a larval food
source for native butterflies
• All cultivars of B.davidii banned in
WA (except for sterile cultivars)
Butterfly bushBuddleja davidii
Class B/Prohibited Plant ListManagement Options
• Hand pull seedlings• recognize early
• Weed Wrench• soil disturbance can sometimes
cause dormant seeds to germinate
• Herbicide–Triclopyr or Glyphosate as a cut
stump treatment
seedling
• Blooming late winter and disappears
by June
• Yellow to white, sometimes orange
flowers
• Reproduces by tubers, bulbils,
bulblets
• Very invasive, streambank erosion,
outcompetes native plants
• Now banned from sale in WA
Lesser CelandineFicaria verna
Class B/Prohibited Plant List
tubersbulbils
2016 Prohibited Plants
Whatcom County - Laurel Baldwin
360-778-6234
Email: [email protected]
http://www.whatcomcounty.us/914/Weeds
WA ST Noxious Weed Control Board:
http://www.nwcb.wa.gov/
King County Noxious Weed Program:
www.kingcounty.gov/environment/animals
AndPlants/noxious-weeds