Identification TipsShowy, bright yellow flowers grow in clusters
near thetop of the plantSoftly hairy leaves and stems on erect
plants growing 3to 6 feet tallLeaves are lance or egg-shaped and
usually 3 in a whorl(sometimes 2 or 4)Flowers have 5 petals that
are joined at the baseThe base of the flowers is ringed by green
sepals thathave distinct orange-brown edgesSeeds found in dry,
egg-shaped capsules
BiologyUpright perennial with roots forming on creeping
stemsthat are partly or entirely underground (rhizomes)Rhizomes can
be up to 15 feet longReproduces by seed and by vegetative
growthSomewhat slow to invade into new areas but onceestablished,
highly competitive and able to spreadaggressively into stands of
established vegetationAble to out-compete even tough plants such as
cattailsand purple loosestrifeThrives in wet sites with full sun
but also shade-tolerantand able to grow in sites that dry out in
the summerFlowers July to August
ImpactsDamages shoreline and wetland ecosystems byreplacing
beneficial native plantsReduces habitat needed by waterfowl,
wildlife, birds andfish, including several species of salmonReduces
recreational opportunities
DistributionOccurs on lakeshores, waterways and in
wetlandsMostly found on Lake Sammamish, Lake Washingtonand the
Sammamish River. Also Lake Burien andin the lower Snoqualmie River
valley.Occasionally found growing as an ornamental
Garden LoosestrifeGarden LoosestrifeGarden LoosestrifeGarden
LoosestrifeGarden Loosestrife Lysimachia vulgaris Primrose
Family
Class B Noxious Weed: Control Required
KING COUNTY NOXIOUS WEED CONTROL PROGRAM WEED ALERT
King County Noxious Weed ControlProgram Line:
206-477-WEEDwww.kingcounty.gov/weeds
Questions?
KING COUNTY NOXIOUS WEED CONTROL PROGRAM WEED ALERT
Garden loosestrife originated fromEurope and has no natural
enemiesin North America.
A large infestation of gardenloosestrife in Marymoor Park
ischoking out native vegetation.
What You Can DoDo your part by checking regularly for garden
loosestrife on your property and along publicwaterways and
wetlands. If a new infestation on public lands is spotted, please
contact the KingCounty Noxious Weed Control program.
Control MethodsMost control methods need to be applied
overseveral years to be successful. Often, a combinationof methods
will be more effective than one by itself.
Prevention: Avoid varieties sold as ornamentals.If boating in
areas with loosestrife, check boat hulls,motors and other equipment
for plant fragments thatcan be transported to new waterways.
Manual: Small infestations can be dug, bagged anddisposed of,
taking care not to disperse seeds. Besure to dig up as much rhizome
as possible. Matureflowering stems can be cut at base in late
summer toprevent seed production. Brush off boots and clothes
before leaving the infested area.
Mechanical: Cutting or mowing by itself is not an effective
control option for garden loosestrife.New shoots and roots will
develop from cut plants. Black plastic covering or landscaping
fabic is aninterim option for dense seedling infestations. It does
not kill mature plants, but it does slow growthand seed
production.
Chemical: Chemical control options may differ for private,
commercial and government agencyusers. Follow all label directions
and local regulations regarding herbicide use in sensitiveareas.
Certain herbicides cannot be used in aquatic areas or their
buffers. If herbicides are used,make sure that their label
specifies your type of site. All aquatic herbicides are
restricted-useherbicides. Purchase and application of these
herbicides can only be done by licensed aquaticherbicide
applicators. Permits are required before applying aquatic
herbicides. Aquatic formulationsof glyphosate or triclopyr are
effective but may require repeat applications. Follow up in the
secondyear is crucial for successful control. For site specific
herbicide recommendations, please contactthe King County Noxious
Weed Control Program.
Don’t be fooledDon’t be fooledDon’t be fooledDon’t be
fooledDon’t be fooled::::: garden loosestrife looks verysimilar to
yellow loosestrife (Lysimachia punctata) andgrows in the same
habitat. It is also somewhat invasive,but has not been elevated to
the same status as gardenand purple loosestrife within King County.
Yellowloosestrife has yellow, star-like blooms all along theflower
stem (not just at the top). Blooms begin in mid-June. It also is
shorter than garden loosestrife, usuallyonly reaching a height of 4
feet.
Garden loosestrife rings lakes and wetlands,out-competing
beneficial vegetation andforming a dense, underground mat
ofrhizomes.
Revised June 2007
Yellow loosestrife(right and below) isoften confused withits
more aggressivecousin, gardenloosestrife.
kingcounty.gov/weeds ~ 206-477-WEED (206-477-9333) or TTY: 711 ~
[email protected]
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