Tag Archives | weed


Purge the surge in spurge!

This past season we have seen a rise in the number of Oblong spurge (Euphorbia oblongata) sites appearing in Clackamas County.  Oblong spurge is a class A noxious weed in the state of Oregon, and eradication of this species is required across the state.  It is known to be highly aggressive and can displace native […]

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What are weeds?

There are a whole host of terms to describe weeds.  The term “weeds” itself can refer to any plant that occurs in an undesirable location. Terms like “non-native“, “exotic“, “alien” or “non-indigenous” refer to plants that occur in areas where they historically did not occur.  These terms make no distinction whether plants are desirable or undesirable.  The term “invasive” refers to a plant or animal that exhibits aggressive growth and displace other species.  Other terms like “noxious” or “nuisance” refers to plants that have special designation by the state or by a municipality the prohibits their sale or cultivation.  With this broad diversity of terms, it is no wonder that many people find themselves confused and wondering how to make sense of it all.

At the WeedWise program we hope to clarify this issue by focusing on plants we refer to as “invasive weeds”Invasive weeds are plants that live outside their historic geographical range, and whose aggressive growth habit has a detrimental effect on our social, economic, or ecologic resources.  The three key components of invasive weeds are that they:

  1. Did not historically occur in our area, but have been brought in either intentionally or unintentionally through human action.
  2. Exhibit aggressive growth which displaces native or desirable vegetation, and will continue to spread unless actively controlled.
  3. Have a negative impact on our community.

These three characteristics clarify invasive weeds as those plants that pose the greatest threat to our community.  By focusing on invasive weeds the WeedWise program is working to maximize its limited resources to realize the greatest benefit to Clackamas County.

Defining our priorities

All invasive weeds pose a major threat to the residents of Clackamas County, but some of these pests can be more damaging than others.  In addition, the costs to control these invasive weeds greatly exceeds the resources available for their management.  As a result, the WeedWise program has prioritized its efforts to target invasive weeds that pose the greatest risk, have the greatest negative impact, and may still be limited enough in their distribution to allow for eradication or containment in Clackamas County.  For these “priority” invasive weeds, the WeedWise program may have resources available to assistance Clackamas County landowners to control or manage these weeds.  For more common invasive weeds, the WeedWise program offers technical information and consultations to improve your efforts and to make your management practices more effective.

Weed Classifications

WeedWise Classification

Priority:  These weeds are the highest priority that are actively being targeted for eradication by the WeedWise Program.  Landowners are encouraged to notify the WeedWise program for assistance with these weeds and to actively control them on their property.
Maintenance:  These weeds are damaging and widespread.  The WeedWise Program encourages control by landowners and can assist with development of a plan to control these weeds.

Oregon Noxious Weed Classification

Class A – a weed of known economic importance which occurs in the state in small enough infestations to make eradication or containment possible; or is not known to occur, but its presence in neighboring states make future occurrence in Oregon seem imminent.  Recommended action: Infestations are subject to eradication or intensive control when and where found.
Class B – a weed of economic importance which is regionally abundant, but which may have limited distribution in some counties. Recommended action: Limited to intensive control at the state, county or regional level as determined on a site specific, case-by-case basis. Where implementation of a fully integrated statewide management plan is not feasible, biological control (when available) shall be the primary control method.
Class T – a priority noxious weed designated by the Oregon State Weed Board as a target for which the ODA will develop and implement a statewide management plan. “T” designated noxious weeds are species selected from either the “A” or “B” list[/quote]

Washington Noxious Weed Classification

Class A noxious weeds are usually newcomers. They are often found in only a few places in the state, and state and local weed boards hope to completely eradicate them before they get a foothold in Washington. Class A weeds are the ones you are least likely to see – but the ones that are most important to report. (If you see a plant you think might be a Class A noxious weed, please report it to your County Weed Board.)

Class B noxious weeds are abundant in some areas of the state, but absent or rare in others. The goal for Class B weeds is to control and reduce their occurrence where they are abundant, and to prevent them from spreading to those parts of the state where they are rare or absent.

Class C Noxious weeds are already widespread in Washington. In some cases, counties may require property owners to control Class C weeds, but more often counties simply try to educate residents about why controlling them is a good idea.

4-County Cooperative Weed Management Area Weed Classification

A = red alert, most invasive, still controllable on a regional or local scale or limited spread
B = most invasive, locally abundant
C = most invasive, widespread
D = less aggressive, wildland invaders, less impact on natural systems
E = aggressive primarily in horticultural/agricultural situations;  note: this category is incomplete
F= needs more info, should be noted if and where it’s a problem
W= watch list

Columbia Gorge CWMA Ranking:

‘A’ Listed Weeds: Early Detection.  Some of these weeds are found outside the CWMA region but could invade the region at any time in the future.  Some have been found in the CWMA in isolated populations.  Management focuses on developing an Early Detection Rapid Response (EDRR) network of people and organizations to identify sites.

‘B’ Listed Weeds: High Importance.  These weeds can be locally abundant, but may also occur in spotty distribution across the landscape.  Management focuses on inventory to determine distribution, followed by eradication of small, isolated populations, and control or containment of larger infestations.

‘C’ Listed Weeds: Common.  These weeds occur across the landscape at a level where eradication, containment or control is not economically feasible.  Management focuses on removing them from ecologically, socially and economically important sites and slowing their spread through prevention actions.  When available, biological controls should be used.

‘W’ Listed Weeds: Watch list.  These weeds display invasive qualities in our area or similar ecosystems, but they have not yet proven to be problematic. Management focuses on inventory to determine if the plant is behaving aggressively followed by eradication or close observation going into the future. The purpose of the “Watch list” is to gather more information on suspect weeds, as well as monitor for occurrence or spread. Information collected may be used to justify future inclusion on the state

Clackamas Weed List

Common NameScientific NameOregon ClassificationWashington ClassificationWeedWise Classification4-County CWMAColumbia Gorge CWMA
VelvetleafAbutilon theophrastiBBBB
Barbed GoatgrassAegilops triuncialisA,Tnot listedpriorityAW
Tree of HeavenAilanthus altissimaBCmaintenanceBC
Garlic mustardAlliaria petiolataB,TApriorityBA
False indigo bush Amorpha fruticosaBBnot listedB
Wild chervilAnthriscus sylvestrisnot listedBmaintenancenot listedB
Italian arumArum italicumnot listedCmaintenanceBB
False bromeBrachypodium sylvaticumBApriorityBA
Butterfly bushBuddleja davidii (Buddleja varabilis)BBmaintenanceBB
Flowering rush Butomus umbellatusA,TApriorityWA
Welted thistleWelted thistleA,Tnot listedprioritynot listednot listed
Drooping sedgeCarex pendulaWnot listedpriorityWB
Meadow knapweedCentaurea × moncktonii (C. pratensis)BBmaintenanceBB
Spotted knapweedCentaurea stoebe (C. maculosa)B,TBmaintenanceBB
Canada thistleCirsium arvenseBCmaintenanceCC
Bull thistleCirsium vulgareBCmaintenanceDC
Old man's beardClematis vitalbaBCmaintenanceBC
Poison hemlockConium maculatumBBmaintenanceBB
English hawthornCrataegus monogynanot listedCmaintenanceCC
Yellow nutsedgeCyperus esculentusBBmaintenanceBB
HoundstongueCynoglossum officinaleBBpriorityDB
Scotch broomCytisus scopariusBBmaintenanceCB
Wild carrot Daucus carotanot listedCmaintenanceCC
Spurge laurelDaphne laureolaBBpriorityBB
Common teaselDipsacus fullonumnot listedCmaintenanceCC
South American waterweedEgeria densaBBmaintenanceCB
Myrtle spurgeEuphorbia myrsinitesBBmaintenanceEB
Oblong spurgeEuphorbia oblongataA,TApriorityAA
GoatsrueGalega officinalisA, TApriorityAA
Shining geraniumGeranium lucidumBBmaintenanceBA
Herb robertGeranium robertianumBBmaintenanceCB
English ivyHedera helixBCmaintenanceCB
Irish ivyHedera hibernicaBCmaintenanceCB
Giant hogweedHeracleum mantegazzianumA, TApriorityAA
Orange hawkweedHieracium aurantiacumA,TBpriorityAA
Meadow hawkweedHieracium caespitosumB,TBpriorityAB
St. John's wort Hypericum perforatumBCmaintenanceCC
Hairy cat's earHypochaeris radicatanot listedCmaintenanceCC
JewelweedImpatiens capensisWCmaintenanceCW
Policeman's helmet Impatiens glanduliferaBBpriorityBB
Yellow flag irisIris pseudacorusBCBB
Yellow archangelLamium galeobdolonBBmaintenanceBB
Large-flowered primrose willowLudwigia grandifloraB, Tnot listedmaintenancenot listedB
Primrose willowLudwigia hexapetalaB, TBmaintenancenot listedB
Water primroseLudwigia peploides ssp. montevidensisB, TAmaintenanceAA
Purple loosestrifeLythrum salicaria BBpriorityBB
Small broomrapeOrobanche minorBnot listedmaintenanceDA
African ruePeganum harmalaA,Tnot listedpriorityAW
RibbongrassPhalaris arundinacea var. pictaB,T Cmaintenancenot listedC
Reed canarygrassPhalaris arundinaceaWCmaintenancenot listedC
Bohemian knotweedFallopia × bohemica ( Polygonum × bohemicum )BBpriorityCB
Japanese knotweedFallopia japonica ( Polygonum cuspidatum )BBpriorityBB
Giant knotweedFallopia sachalinensis ( Polygonum sachalinensis )BBpriorityBB
Curly-leaf pondweedPotamogeton crispusnot listedCmaintenanceCC
Sulphur cinquefoilPotentilla rectaBBpriorityAB
Lesser celandineRanunculus ficariaBBmaintenanceBB
Armenian (Himalayan) blackberryRubus armeniacus (R. bifrons, R. procerus, R. discolor)BCmaintenanceCC
Evergreen blackberryRubus laciniatusnot listedCmaintenanceCC
Tansy ragwortSenecio jacobaeaBBmaintenanceBB
Common groundselSenecio vulgarisnot listedCmaintenancenot listedC
Blessed milk thistleSilybum marianumBApriorityAA
Perennial sowthistleSonchus arvensis ssp. arvensisnot listedCmaintenanceDC
Common tansyTanacetum vulgarenot listedCmaintenanceCC
Garden yellow loosestrifeLysimachia vulgarisA,TBpriorityAW
Spiny cockleburXanthium spinosumBCpriorityDC
Syrian bean-caperZygophyllum fabagoAApriorityAA
Biddy-biddyAcaena novae-zelandiaeBnot listednot listedW
Russian KnapweedAcroptilon repensBBpriorityAB
Pheasant eyeAdonis aestivalisBnot listedprioritynot listednot listed
Jointed goatgrassAegilops cylindricaBCprioritynot listedC
Ovate GoatgrassAegilops ovataAnot listedpriorityAW
CamelthornAlhagi pseudalhagiABpriorityAA
BlackgrassAlopecurus myosuroidesnot listedCAW
Yellow tuftAlyssum corsicumA,Tnot listedpriorityAW
Yellow tuftAlyssum muraleA,Tnot listedpriorityAW
RagweedAmbrosia artemisiifoliaBnot listedpriorityDB
Skeletonleaf bursageAmbrosia tomentosaAnot listedpriorityAnot listed
Annual buglossAnchusa arvensisnot listedBnot listedB
Common buglossAnchusa officinalisB,TBpriorityAB
Absinth wormwoodArtemisia absinthiumnot listedCnot listedC
South African capeweedArtotheca calendulaWnot listednot listedW
Giant reedArundo donaxWnot listedprioritynot listedA
Common barberryBerberis vulgarisnot listedCnot listedW
Hoary allysumBertoa incanaA,TBpriorityAB
White bryoniaBryonia albaABpriorityAA
FanwortCabomba caroliniananot listedBnot listedW
Plumeless thistleCarduus acanthoidesA,TBpriorityAA
Musk thistleCarduus nutansBBpriorityEB
Italian thistleCarduus pycnocephalusBApriorityDA
Slender-flowered thistleCarduus tenuiflorusBApriorityDA
Smooth distaff thistleCarthamus baeticusAnot listedpriorityAW
Woolly distaff thistleCarthamus lanatusA,Tnot listedpriorityAW
Whitestem distaff thistleCarthamus leucocaulosWnot listednot listedW
Wild safflowerCarthamus oxyacanthaWnot listednot listedW
Longspine sandburCenchrus longispinusnot listedCnot listedC
Purple starthistleCentaurea calcitrapaA,TApriorityAA
Diffuse knapweedCentaurea diffusaBBBB
Iberian starthistleCentaurea ibericaA,Tnot listedpriorityAA
Brown knapweedCentaurea jacea not listedBFB
Big-headed knapweedCentaurea macrocephalaWAnot listedA
Malta starthistleCentaurea melitensisnot listedBnot listednot listed
Black knapweedCentaurea nigra not listedBnot listedB
Vochin knapweedCentaurea nigrescensnot listedAnot listedA
Yellow starthistleCentaurea solstitialisBBpriorityAB
Feather-headed knapweedCentaurea trichocephalaWnot listednot listedW
Squarrose knapweedCentaurea virgataA,Tnot listedprioritynot listedA
Rush skeletonweedrChondrilla junceaB, TBpriorityDB
Oriental clematisClematis orientalisnot listedAnot listedA
Field bindweedConvolvulus arvensisB,TCCC
Jubata grassCortaderia jubataBCpriorityWB
Pampass grassCortaderia selloananot listedCnot listedC
Common crupinaCrupina vulgarisBAnot listedW
Smoothseed alfalfa dodderCuscuta approximataBCnot listedC
Bigseed dodderCuscuta indecoraBnot listednot listednotlisted
Japanese dodder Cuscuta japonicaAnot listedpriorityAW
Five-angled dodderCuscuta pentagonaBnot listednot listednotlisted
Purple nutsedgeCyperus rotundusAnot listedpriorityAA
Portuguese broomCytisus striatusB,Tnot listedWW
Cape ivyDelairea odorataAnot listedpriorityAW
Cutleaf teaselDipsacus laciniatusBnot listedprioritynot listedW
Tree echiumEchium pininanaWnot listednot listedW
Paterson's curseEchium plantagineumA,Tnot listedpriorityAW
Viper buglossEchium vulgareWBnot listedB
Water hyacinthEichhornia crassipesWnot listednot listednot listed
Russian oliveElaeagnus angustifolianot listedCnot listedC
Hairy willow-herbEpilobium hirsutum not listedBnot listedB
Spanish heath Erica lusitanicaBnot listedWW
Toothed spurgeEuphorbia dentataWnot listednot listedW
Leafy spurgeEuphorbia esulaB, TBpriorityBA
Common fennelFoeniculum vulgarenot listedBCB
French broomGenista monspessulanaBAWA
Reed sweetgrassGlyceria maximanot listedAnot listedA
BabysbreathGypsophila paniculatanot listedCnot listedC
HalogetonHalogeton glomeratusBnot listedprioritynot listedW
Texas blueweedHelianthus ciliarisnot listedAnot listedA
SpikeweedHemizonia pungensBCprioritynot listedC
Yellow hawkweedHieracium × floribundumA,TBpriorityAA
Polar hawkweedHieracium atratumnot listedBnot listedW
Whiplash hawkweedHieracium flagellarenot listedBnot listedW
Queen-devil hawkweedHieracium glomeratumnot listedBnot listedW
Common hawkweedHieracium lachenaliinot listedBnot listedB
Pale hawkweedHieracium lactucellanot listedBnot listedW
Smooth hawkweedHieracium laevigatumnot listedBnot listedW
Spotted hawkweedHieracium maculatumnot listedBnot listedW
Wall hawkweedHieracium murorumnot listedBWW
Mouse-ear hawkweedHieracium pilosellaA,TBpriorityAA
King-devil hawkweedHieracium piloselloidesA,TBpriorityAA
European hawkweedHieracium sabaudumnot listedBnot listedW
HydrillaHydrilla verticillataAApriorityWA
Common frogbitHydrocharis morsus-ranaeAnot listedpriorityAW
Black henbaneHyoscyamus nigernot listedCnot listedC
Small-flowered jewelweedImpatiens parvifloranot listedApriorityAA
Dyers woadIsatis tinctoriaBAnot listedA
KochiaKochia scopariaBBprioritynot listedB
Perennial peavineLathyrus latifoliusBnot listedmaintenanceCC
Lens-podded whitetopLepidium chalepensisBnot listedpriorityAB
Hoary cressLepidium drabaBCpriorityAB
Perennial pepperweedLepidium latifoliumB,TBpriorityAB
Hairy whitetopLepidium pubescensBCprioritynot listedC
LepyrodiclisLepyrodiclis holosteoidesnot listedCnot listedW
Oxeye daisyLeucanthemum vulgarenot listedCmaintenanceCC
West Indian spongeplantLimnobium laevigatumAnot listedpriorityAW
Dalmatian toadflaxLinaria dalmaticaB, TBBB
Yellow toadflaxLinaria vulgarisBCmaintenanceBC
Rose campionLychnus coronariaWnot listednot listedW
Wand loosestrifeLythrum virgatum not listedBnot listedW
Scentless mayweedMatricaria perforatanot listedCnot listedC
Wild four o'clockMirabilis nyctagineanot listedAnot listedW
Variable-leaf milfoilMyriophyllum heterophyllumnot listedAnot listedA
Eurasian watermilfoilMyriophyllum spicatumBBpriorityCB
Hybrid watermilfoil Myriophyllum spicatum × M. sibiricum not listedCnot listednot listed
Parrots featherMyrophyllum aquaticumBBmaintenanceBB
MatgrassNardus strictaA,Tnot listedpriorityAW
Fragrant water lilyNymphaea odoratanot listedCDC
Yellow floating heartNymphoides peltataA, TBpriorityAA
Scotch thistleOnopordum acanthiumBBpriorityAB
Taurian thistleOnopordum tauricumA,Tnot listedpriorityAW
Mile-a-minute weedPersicaria perfoliataWnot listednot listedW
Japanese butterburPetasites japonicanot listednot listedWB
Common reed Phragmites australis ssp. australisBBpriorityAB
American pokeweedPhytolacca americanaWnot listedBA
Hawkweed oxtonguePicris hieracioides not listedBnot listedB
Himalayan knotweedPolygonum polystachyumBBprioritynot listedB
KudzuPueraria montanaA,TApriorityAA
Austrian fieldcressRorippa austriacanot listedCnot listedC
Creeping yellow cressRorippa sylvestrisBnot listednot listedA
Sweet briar roseRosa rubiginosa ( R.eglanteria )Wnot listednot listedW
RavennagrassSaccharum ravennaeAApriorityAA
Grass-leaved arrowheadSagittaria graminea not listedBnot listedW
Delta arrowheadSagittaria platyphyllaAnot listedAnot listed
Mediterranean sageSalvia aethiopisBAnot listedA
Meadow clarySalvia pratensisnot listedAnot listedW
Clary sageSalvia sclareaWAnot listedW
Ricefield bulrushSchoenoplectus mucronatusWADA
Cereal ryeSecale cerealenot listedCnot listedC
White cockleSilene latifolia ssp. albanot listedCnot listedC
Silverleaf nightshadeSolanum elaeagnifoliumAApriorityAA
BuffaloburSolanum rostratumBCpriorityDC
Sticky nightshadeSolanum sisymbriifoliumWnot listednot listedW
Field BurrweedSoliva sessilisnot listedCnot listedW
JohnsongrassSorghum halepenseBApriorityEA
Smooth cordgrassSpartina alternifloraA, TApriorityAW
Common cordgrassSpartina anglicaA,TApriorityAW
Dense-flowered cordgrassSpartina densifloraA,TApriorityAW
Saltmeadow cordgrassSpartina patensA,TApriorityAW
Spanish broomSpartium junceumBApriorityFA
SwainsonpeaSphaerophysa salsulaBCnot listedC
Water soldiersStratiotes aloidesAnot listedpriorityAnot listed
Medusahead ryeTaeniatherum caput-medusaeBnot listedpriorityCC
SaltcedarTamarix ramosissimaB,TBWB
Spurge flaxThymelaea passerinanot listedBnot listedW
European water chestnutTrapa natansAnot listedpriorityAA
PuncturevineTribulus terrestrisBBpriorityCB
ColtsfootTussilago farfaraABpriorityAA
Narrowleaf cattailTypha angustifolianot listedCnot listedC
Southern cattailTypha domingensisnot listedCnot listedW
Miniature cattailTypha minimanot listedCnot listedW
White cattailTypha x glaucanot listedCnot listedW
GorseUlex europaeusB,TBpriorityAA
North Africa grassVentenata dubia ( V. avenacea )BCnot listedC
Japanese eelgrassZostera japonicaWCnot listedW


The WeedWise Program is dedicated to helping protect Clackamas County from the ongoing threat of invasive weeds.  These projects are often based around the prevention or management or priority invasive weeds. We currently working on projects across the county, but focus largely on priority invasive weeds, priority sites, or on partnership projects.

Priority Weed Control Projects

Orange hawkweed control is an example of a priority weed control project underway at several locations in Clackamas County.

The priority weed control program focuses on the Early Detection and Rapid Response (EDRR) of new or rare invasive weeds where the goal is either eradication or containment.  These projects allow us to focus our resources for maximum impact.  Priority weed control projects typically occur at the landscape level and impact multiple landowners either public or private.  These project focus on the control and eradication of a priority weed species.  Some examples of our current priority weed control projects include the active management of:

  • Garlic mustard (Alliaria petiolata)
  • False brome (Brachypodium sylvaticum)
  • Spurge laurel (Daphne laureola)
  • Oblong spurge (Euphorbia oblongata)
  • Japanese, Giant, and Bohemian knotweed (Fallopia japonica, F. sachalinensis, and F. x bohemica)
  • Goatsrue (Galega officinalis)
  • Orange hawkweed (Hieracium aurantiacum)
  • Giant hogweed (Heracleum mantegazzianum)
  • Policeman’s helmet (Impatiens glandulifera)
  • Blessed Milk Thistle (Silybum marianum)
  • Puncturevine (Tribulus terrestris)
  • Gorse (Ulex europaeus)

The priority weed control projects are one of our highest priorities and target all known infestations across the county or within a given management area.

Priority Site Projects

The Bull Run Gate Project was initiated to protect the city of Portland’s municipal watershed from encroaching birds dispersed invasive weeds

Priority site projects are projects that are designed to protect areas of exceptional quality or of unique ecological, economic, or cultural importance.   Some examples of projects that the WeedWise program is currently working on or have spearheaded in the past include:

  • Barton Area Priority weeds project
  • Bull Run Gate weed control project
  • Coral Creek weed control project
  • Molalla River confluence project
  • Newell Creek restoration project
  • Salmon River priority weed control project
  • South Creek-Abernethy project
  • Lolo Pass priority weed control project

The priority site project areas are typically local or regional significance and are designed to protect or buffer these areas from  the encroachment or spread of invasive weeds.  The goals of these projects is typically focused on exclusion and maintenance of natural areas within the project areas.

Partnership Projects

Knotweed control efforts undertaken in conjunction with the Clackamas River Invasive Species Partnership, focus area project.

Partnership project are those projects that are typically undertaken in conjunction with local and regional partners.  These projects are often complex and have diverse interests.  These projects involve working in cooperation with partner organizations to implement projects across broad geographic areas or across jurisdictional boundaries.  Examples of partnership projects include:

Learn More

To learn more about our projects please check the project drop downs in the navigation menu above, or contact us about information pertaining to a particular project mentioned.

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