Invasiveness Ranking System for Non-Native Plants of Alaska

Extent of the species U.S. range and/or occurrence of5formal state or provincial listing (0–5)Common dandelion occurs in all 50 states and almost allCanadian provinces (USDA 2002). It is a noxious weed inAlberta, Manitoba, Quebec, and Saskatchewan (InvadersDatabase System 2003). It has been reported from all threeprimary ecogeographic regions of Alaska (Hultén 1968,University of Alaska Museum 2003).Total for Ecological Amplitude and Distribution 18/25Feasibility of ControlScoreSeed banks (0–3) 3Common dandelion creates a long-lived seed bank (Esser 1993,Pratt 1984). The seeds of common dandelion were viable up to 5years in soil samples from Montana (Bard 1952), and up to 9 yearsin experiments in Nebraska (Burnside et al. 1996).Vegetative regeneration (0–3) 2Common dandelion sprouts from caudex and root crowns(Densmore et al. 2001, Staniforth and Scott 1991, Whitson et al.2000). Reproduction from cut pieces is possible (Rutledge andMcLendon 1996).Level of effort required (0–4) 3Common dandelion can be controlled with repeated chemicaland mechanical control measures. Seeding a mixture of nativespecies after treatment is recommended (Densmore et al. 2001,MAFRI 2004).Total for Feasibility of Control 8/10Total score for 4 sections 58/100§Tanacetum vulgare L.Ranking SummaryEcoregion known or expected to occur inSouth CoastalInterior BorealArctic AlpineYesYesYesPotential Max. ScoreEcological Impact 40 20Biological Characteristics and Dispersal 23 15Amplitude and Distribution 25 15Feasibility of Control 10 8Relative Maximum 57Climatic ComparisonCollected inAlaska regions?common names: common tansy, garden tansyCLIMEXsimilarity?South Coastal Yes –Interior Boreal Yes –Arctic Alpine No YesTanacetum vulgare has been collected in the south coastal andinterior boreal ecogeographic regions (Welsh 1974, AKEPIC2004, UAM 2004). It is widely planted as ornamental inAnchorage and Matanuska–Susitna Valleys. The range ofcommon tansy includes lowlands and mountain valleys north of70°N (the provinces of Finnmark and Troms in Norway) (Lidand Lid 1994). These regions are north of the Arctic Circle, andinclude tundra habitats. It is possible for tansy to establish inAlaska’s arctic alpine ecogeographic regions.Ecological ImpactScoreImpact on Ecosystem Processes (0–10) 5Common tansy often grows along streams, watercourses, andditches where it can restrict waterflow (CWMA 2004).Impact on Natural Community Structure (0–10) 5Common tansy is not known to cause major impacts on naturalcommunity structure (U.S. Department of the Interior 2004). InAlaska, it can establish in the existing herbaceous layer and alterthe density of the layer (I. Lapina pers. obs.).Impact on Natural Community Composition (0–10) 5Common tansy is likely to affect the availability of water andsoil nutrients, therefore, may cause a reduction in the numberof individuals of other species (U.S. Department of the Interior2004).Impact on Higher Trophic Levels (0–10) 5Common tansy has been reported as unpalatable to moderatelypoisonous; therefore, infestations can alter the quantity offoraging sites (CWMA 2004, Royer and Dickinson 1999, Plantsfor a Future 2002). It is an alternate host for viruses (Royer andDickinson 1999).Total for Ecological Impact 20/40Biological Characteristics and Dispersal ScoreMode of Reproduction (0–3) 3Common tansy reproduces by both seed and stoloniferousrhizomes. Each plant is capable of producing over 50,000 seeds(Royer and Dickinson 1999, Whitson et al. 2000). It is quiteaggressive in its vegetative spread (Plants for a Future 2002).Long-distance dispersal (0–3) 0The seeds of common tansy have no adaptation for long-distancedispersal (Royer and Dickinson 1999).Spread by humans (0–3) 3Common tansy has been used as ornamental and medicinalremedy. It has escaped and become widely established. It alsois a potential contaminant in commercial seed (CWMA 2004,USDA, ARS 2004).Allelopathic (0–2)UUnknownCompetitive Ability (0–3) 1Common tansy is a moderately successful competitor (U.S.Department of the Interior 2004).Thicket-forming/Smothering growth form (0–2) 2The plant can grow up to 6 feet tall and it is usually taller thansurrounding herbaceous vegetation (Royer and Dickinson 1999,Whitson et al. 2000). Its extensive rhizomatous growth cancreate dense stands.Germination requirements (0–3) 2Common tansy is known to germinate in vegetated areas (U.S.Department of the Interior 2004).Other invasive species in the genus (0–3) 3Tanacetum corymbosum (L,) Schultz-Bip. and Tanacetumparthenium (L.) Schultz-Bip. (ITIS 2002).B-129