Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Linaria dalmatica
(dalmatian toadflax)

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Datasheet

Linaria dalmatica (dalmatian toadflax)

Summary

  • Last modified
  • 16 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Host Plant
  • Preferred Scientific Name
  • Linaria dalmatica
  • Preferred Common Name
  • dalmatian toadflax
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae
  • Summary of Invasiveness
  • L. dalmatica is a herbaceous plant native to western Asia and south east Europe. It is of particular concern in North America where it was introduced in the late nineteenth century. It has since spread across m...

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Pictures

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PictureTitleCaptionCopyright
Linaria dalmatica (dalmatian toadflax); flowering habit. USA.
TitleHabit
CaptionLinaria dalmatica (dalmatian toadflax); flowering habit. USA.
Copyright©Eric Coombs/Oregon Department of Agriculture/Bugwood.org - CC BY 3.0 US
Linaria dalmatica (dalmatian toadflax); flowering habit. USA.
HabitLinaria dalmatica (dalmatian toadflax); flowering habit. USA.©Eric Coombs/Oregon Department of Agriculture/Bugwood.org - CC BY 3.0 US
Linaria dalmatica (dalmatian toadflax); urban infestation, showing habit. Burns, Oregon, USA. June 2013.
TitleInfestation
CaptionLinaria dalmatica (dalmatian toadflax); urban infestation, showing habit. Burns, Oregon, USA. June 2013.
Copyright©Eric Coombs-2013/Oregon Department of Agriculture/Bugwood.org - CC BY 3.0 US
Linaria dalmatica (dalmatian toadflax); urban infestation, showing habit. Burns, Oregon, USA. June 2013.
InfestationLinaria dalmatica (dalmatian toadflax); urban infestation, showing habit. Burns, Oregon, USA. June 2013.©Eric Coombs-2013/Oregon Department of Agriculture/Bugwood.org - CC BY 3.0 US
Linaria dalmatica (dalmatian toadflax); close view of flowers. USA.
TitleFlowers
CaptionLinaria dalmatica (dalmatian toadflax); close view of flowers. USA.
Copyright©Eric Coombs/Oregon Department of Agriculture/Bugwood.org - CC BY 3.0 US
Linaria dalmatica (dalmatian toadflax); close view of flowers. USA.
FlowersLinaria dalmatica (dalmatian toadflax); close view of flowers. USA.©Eric Coombs/Oregon Department of Agriculture/Bugwood.org - CC BY 3.0 US
Linaria dalmatica (dalmatian toadflax); foliage. USA.
TitleLeaves
CaptionLinaria dalmatica (dalmatian toadflax); foliage. USA.
Copyright©Bonnie Million/National Park Service/Bugwood.org - CC BY-NC 3.0 US
Linaria dalmatica (dalmatian toadflax); foliage. USA.
LeavesLinaria dalmatica (dalmatian toadflax); foliage. USA.©Bonnie Million/National Park Service/Bugwood.org - CC BY-NC 3.0 US
Linaria dalmatica (dalmatian toadflax); seeds. USA.
TitleSeeds
CaptionLinaria dalmatica (dalmatian toadflax); seeds. USA.
Copyright©Steve Hurst/USDA NRCS PLANTS Database/Bugwood.org - CC BY-NC 3.0 US
Linaria dalmatica (dalmatian toadflax); seeds. USA.
SeedsLinaria dalmatica (dalmatian toadflax); seeds. USA.©Steve Hurst/USDA NRCS PLANTS Database/Bugwood.org - CC BY-NC 3.0 US
Linaria dalmatica (dalmatian toadflax); seedlings. USA.
TitleSeedlings
CaptionLinaria dalmatica (dalmatian toadflax); seedlings. USA.
Copyright©Linda Wilson/University of Idaho/Bugwood.org - CC BY-NC 3.0 US
Linaria dalmatica (dalmatian toadflax); seedlings. USA.
SeedlingsLinaria dalmatica (dalmatian toadflax); seedlings. USA.©Linda Wilson/University of Idaho/Bugwood.org - CC BY-NC 3.0 US

Identity

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Preferred Scientific Name

  • Linaria dalmatica (L.) Mill.

Preferred Common Name

  • dalmatian toadflax

Other Scientific Names

  • Antirrhinum dalmaticum L.
  • Linaria dalmatica var. dalmatica
  • Linaria genistifolia subsp. dalmatica (L.) Maire & Petitm.

International Common Names

  • English: balkan toadflax; broadleaf toadflax

Local Common Names

  • Germany: leinkraut dalmatinische
  • Portugal: linaria-dalmática
  • Sweden: jättesporre

EPPO code

  • LINDA (Linaria genistifolia subsp. dalmatica)

Summary of Invasiveness

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L. dalmatica is a herbaceous plant native to western Asia and south east Europe. It is of particular concern in North America where it was introduced in the late nineteenth century. It has since spread across most of the western areas of the USA and Canada (De Clerck-Floate and Turner, 2013). There it has invaded rangelands, rights-of-way and natural habitats. It is classified as noxious in many of the western states of both countries. It is also classed as invasive in South Africa. Its success may be attributed to its high specific leaf area, aggressive root system, prolific seed production and the presence of alkaloids which discourages grazing by livestock, thus allowing it to become dominant (De Clerck-Floate and Turner, 2013).

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Scrophulariales
  •                         Family: Scrophulariaceae
  •                             Genus: Linaria
  •                                 Species: Linaria dalmatica

Notes on Taxonomy and Nomenclature

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This species was named Antirrhinum dalmaticum by Linnaeus, but was moved to the genus Linaria as L. dalmatica by Philip Miller in 1768 and that name has been widely accepted. The Royal Botanic Garden Edinburgh (2015) and some other authorities however now use L. genistifolia subsp. dalmatica. The genus Linaria was previously included in the family Scrophulariaceae. Many sources still use this classification but a series of genetic studies resulted in the ‘disintegration’ of the old Scrophulariaceae such that, apart from all the parasitic members of the family being transferred to the Orobanchaceae, Linaria along with Antirrhinum and Scrophularia were transferred to Plantaginaceae (Judd et al., 1999; Olmstead et al., 2001; Judd et al., 2002; APG, 2003). The genus comprises about 100 species.

Two naturally occurring varieties are recognized, L. dalmatica var. dalmatica and L. dalmatica var. macedonica. The latter, sometimes treated as a subspecies, occurs only in Macedonia (Vujnovic and Wein, 2005). There is a further range of horticultural varieties.

A narrow leaved variant mentioned in some publications is now considered to be the related but distinct L. genistifolia, known as narrowleaf or broomleaf toadflax.

Zouhar (2003) reported that hybrids with L. vulgaris had been created in the laboratory. This was later confirmed in the wild in Montana, USA by Ward et al. (2009) with hybrids being viable and fertile.

Description

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L. dalmatica is a robust, glaucous, herbaceous perennial with taproots enlarged above, more or less woody, deeply penetrating (1.8 m or more into the ground), spreading by horizontal roots 5–20 cm below the surface, spreading up to 3.6 m from the plant. Adventitious offshoots from these roots are generally sterile, decumbent to weakly ascending, succulent, 3–40 per crown. Stems from the main crown are annual, 40–100 cm high, ascending to erect, more or less woody near the ground. Leaves are alternate, often in two’s or three’s on lower part of the stem, sessile, reflexed to ascending, entire, acute to acuminate at the tip, obtuse to cordate at the base, sometimes concave above, usually amplexicaul, somewhat leathery, glabrous and sometimes rugose, with 3–7 longitudinal veins on lower surface. The lower leaves are 1-5 cm long, up to 1 cm wide, linear to lanceolate; the upper leaves 3–6 cm long, 1-4 cm wide, lanceolate to very broad-ovate. Bracts are similar to upper leaves, or smaller. Flowers are in erect or nodding, simple racemes, usually loose, sometimes compact; 15–55 cm long on pedicels 1–8 mm long. Five sepals, valvate or somewhat imbricate, erect, lanceolate acute to acuminate, 0.7–1.1 cm long, 0.2–0.4 cm wide, margins entire to somewhat undulate. The corolla, including spur 3.3–4.5 cm long, light yellow to yellow, rarely nearly white; tube 6–9 mm long, the upper lip bilobate, often somewhat helmet-shaped, the lower lip trilobate; spur tapered, 1.2–1.8 cm long, straight or slightly curved; four fertile stamens adnate in pairs, didynamous 0.8–1.5 cm long, one reduced staminode; pistil bicarpellate; ovary bilaterally symmetrical ca. 2 mm diameter at anthesis, abruptly narrowed to the terminal style; style filiform, erect, stigma single, terminal, hemispherical; numerous ovules in each locule; capsule long ovoid to nearly spherical, 4–10 mm long, 4–8 mm in diameter, dehiscing terminally on each carpel. Seeds black to purplish-brown, triquetrous or somewhat compressed, muricate-rugose on the surface, 0.7–1.3 mm wide, 30–170 per locule; each seed with narrow wing on the angles. The species is morphologically highly variable (this description simplified from Vujnovic and Wein, 2005, based on original by Alex, 1962).

Plant Type

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Broadleaved
Herbaceous
Perennial
Seed propagated
Vegetatively propagated

Distribution

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The native distribution of L. dalmatica is restricted to the Balkan Peninsula, Turkey, Iran, Iraq, Syria and Romania. The Royal Botanic Garden Edinburgh (2015) notes that it is locally naturalized in Central Europe therefore, the records from Germany and Hungary presumably refer to introductions. It also occurs as an occasional escape from gardens in Switzerland, UK and elsewhere in Europe. It is now widely naturalized and invasive across Canada and western USA (Leo’s Dictionaries, 2015). L. dalmatica has more recently been spreading in South Africa (Invasive Species South Africa, 2015) and has also naturalized in Australia (Parsons and Cuthbertson, 1992) and in Argentina (Puntieri and Brion, 2003). As it is widely cultivated in gardens, it is likely to occur as an occasional escape in many other countries.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

IndiaPresentPresent based on regional distribution.
-Indian PunjabPresentIntroducedUSDA-NRCS, 2015
IranPresentNativeUSDA-ARS, 2015
IraqPresentNativeVujnovic and Wein, 2005
SyriaPresentNativeVujnovic and Wein, 2005
TurkeyPresentNativeUSDA-ARS, 2015

Africa

South AfricaLocalisedIntroduced Invasive GBIF, 2015

North America

CanadaWidespreadHolm et al., 1979; Vujnovic and Wein, 2005
-AlbertaPresentIntroduced Invasive Vujnovic and Wein, 2005
-British ColumbiaWidespreadIntroduced Invasive Vujnovic and Wein, 2005
-ManitobaPresentIntroducedVujnovic and Wein, 2005
-New BrunswickLocalisedIntroducedVujnovic and Wein, 2005
-Newfoundland and LabradorLocalisedIntroducedVujnovic and Wein, 2005
-Nova ScotiaLocalisedIntroducedVujnovic and Wein, 2005
-OntarioPresentIntroducedVujnovic and Wein, 2005
-Prince Edward IslandLocalisedIntroducedVujnovic and Wein, 2005
-QuebecPresentIntroducedVujnovic and Wein, 2005
-SaskatchewanWidespreadIntroducedVujnovic and Wein, 2005
-Yukon TerritoryLocalisedIntroducedBennett et al., 2010
USAPresentIntroducedHolm et al., 1979; Vujnovic and Wein, 2005
-ArizonaPresentIntroducedUSDA-NRCS, 2015
-ArkansasPresentIntroducedUSDA-NRCS, 2015
-CaliforniaPresentIntroduced Invasive USDA-NRCS, 2015
-ColoradoPresentIntroduced Invasive USDA-NRCS, 2015
-ConnecticutPresentIntroducedUSDA-NRCS, 2015
-DelawarePresentIntroducedUSDA-NRCS, 2015
-District of ColumbiaPresentIntroducedUSDA-NRCS, 2015
-IdahoPresentIntroducedUSDA-NRCS, 2015
-IllinoisPresentIntroducedUSDA-NRCS, 2015
-IowaPresentIntroduced
-KansasPresentIntroducedUSDA-NRCS, 2015
-MainePresentIntroducedUSDA-NRCS, 2015
-MarylandPresentIntroducedUSDA-NRCS, 2015
-MassachusettsPresentIntroducedUSDA-NRCS, 2015
-MichiganPresentIntroducedUSDA-NRCS, 2015
-MinnesotaPresentIntroducedUSDA-NRCS, 2015
-MontanaWidespreadIntroduced Invasive USDA-NRCS, 2015
-NebraskaPresentIntroducedUSDA-NRCS, 2015
-NevadaPresentIntroducedUSDA-NRCS, 2015
-New HampshirePresentIntroducedUSDA-NRCS, 2015
-New JerseyPresentIntroducedUSDA-NRCS, 2015
-New MexicoPresentIntroducedUSDA-NRCS, 2015
-New YorkPresentIntroducedUSDA-NRCS, 2015
-North DakotaPresentIntroducedUSDA-NRCS, 2015
-OhioPresentIntroducedUSDA-NRCS, 2015
-OklahomaPresentIntroducedUSDA-NRCS, 2015
-OregonPresentIntroducedUSDA-NRCS, 2015
-PennsylvaniaPresentIntroducedUSDA-NRCS, 2015
-Rhode IslandPresentIntroducedUSDA-NRCS, 2015
-South DakotaPresentIntroducedUSDA-NRCS, 2015
-UtahPresentIntroducedUSDA-NRCS, 2015
-VermontPresentIntroducedUSDA-NRCS, 2015
-WashingtonWidespreadIntroducedUSDA-NRCS, 2015
-WisconsinPresentIntroducedUSDA-NRCS, 2015
-WyomingPresentIntroducedUSDA-NRCS, 2015

South America

ArgentinaLocalisedIntroducedPuntieri and Brion, 2003

Europe

AlbaniaPresentNativeUSDA-ARS, 2015
BulgariaPresentNativeUSDA-ARS, 2015
CroatiaPresentNativeGBIF, 2015
FranceLocalisedNativeGBIF, 2015
GermanyLocalisedIntroducedGBIF, 2015
GreecePresentNativeUSDA-ARS, 2015
HungaryLocalisedIntroducedGBIF, 2015
ItalyLocalisedIntroducedVujnovic and Wein, 2005; Royal Botanic Garden Edinburgh, 2015
RomaniaPresentNativeRoyal Botanic Garden Edinburgh, 2015; USDA-ARS, 2015
SwitzerlandLocalisedIntroducedLeo's Dictionaries, 2015
UKPresentIntroducedStace, 1991; Leo's Dictionaries, 2015
Yugoslavia (former)PresentNativeRoyal Botanic Garden Edinburgh, 2015

Oceania

AustraliaLocalisedIntroduced1933Parsons and Cuthbertson, 1992
-New South WalesLocalisedIntroducedParsons and Cuthbertson, 1992

History of Introduction and Spread

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L. dalmatica is believed to have been introduced to western USA by the late nineteenth or early twentieth century and had become naturalized in California by 1920. In Canada it was first planted in Ottawa in 1901 and was reported as naturalized in Alberta by 1933 (Vujnovic and Wein, 2005).

Risk of Introduction

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The risk of introduction of L. dalmatica continues to be high, though there must be few temperate countries to which it has not already been introduced as an ornamental. Thus the risk of spread is mainly accidental, from careless disposal of material from gardens.

Habitat

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In its native range L. dalmatica is a plant of uncultivated fields, vineyards, roadsides and waste places, mainly on coarse textured soils. It may occur on limestone hills and generally favours alkaline soils. In North America, its introduced range, it occurs in similar habitats but has also invaded forest plantations, wood and herbaceous species in the genus Artemisia, pastures, rangelands and to some extent crops such as lucerne/alfalfa (Medicago sativa) (Vujnovic and Wein, 2005).

L. dalmatica has a wide temperature tolerance but on a mountain area in Canada, establishment on disturbed roadsides was limited by the low temperatures experienced at higher elevation (Polinac and Rew, 2014).

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Terrestrial
 
Terrestrial – ManagedCultivated / agricultural land Secondary/tolerated habitat Harmful (pest or invasive)
Managed forests, plantations and orchards Secondary/tolerated habitat
Managed grasslands (grazing systems) Principal habitat Harmful (pest or invasive)
Disturbed areas Present, no further details Harmful (pest or invasive)
Rail / roadsides Principal habitat Harmful (pest or invasive)
Terrestrial ‑ Natural / Semi-naturalNatural forests Secondary/tolerated habitat
Natural grasslands Present, no further details Harmful (pest or invasive)
Riverbanks Present, no further details Harmful (pest or invasive)
Scrub / shrublands Secondary/tolerated habitat
Deserts Present, no further details Harmful (pest or invasive)
Littoral
Coastal areas Present, no further details

Hosts/Species Affected

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The crops affected by L. dalmatica are mainly pasture and rangeland species, but alfalfa (Medicago sativa) and forest species such as ponderosa pine (Pinus ponderosa) may also be affected.

Host Plants and Other Plants Affected

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Plant nameFamilyContext
Medicago sativa (lucerne)FabaceaeMain
Pinus ponderosa (ponderosa pine)PinaceaeOther

Biology and Ecology

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Genetics

The chromosome number 2n = 12 has been reported for L. dalmatica (Missouri Botanical Garden, 2015).

Reproductive Biology

L. dalmatica spreads both by seed and by its spreading root system. The shoots arising from the roots are described as ‘sterile’, but presumably will develop fully if separated from the parent plants.

Under laboratory conditions some seeds will germinate the same season in which produced. Germination from dry storage increases for two to three years, with a periodic low in November and a high in April. Over 90% germination is obtained with two to three year old seeds in the laboratory. In the field, germination occurs in both spring and autumn and seedlings can emerge from a soil depth of 2-2.5 cm. Seeds may be dormant for a few weeks after maturation. Thereafter they have no particular requirement (Robocker, 1970).

Seedlings which emerge in the autumn generally do not survive the following year. Most emergences occur in the spring, following stratification over winter. Cyclic alterations of 10 days stratification at 2°C and 10 days drying at room temperature for two cycles induced higher rates of germination than did any other factor. The highest germination of seeds planted at different depths in five soil textures was found to be from a depth of 1.27 cm in loamy sand (Alex, 1962). Seeds germinate from 2.5 cm in clay and loamy soils and from 5 cm in sandy soils. Seedling recruitment can be seriously reduced by plant competition (Grieshop and Nowierski, 2002).

Shoots growing from the crown flower from May and fruit by August, producing large numbers of seeds, up to 250 per capsule and up to 500,000 per plant. The flowers are self-sterile and are insect pollinated (Vujnovic and Wein, 2005). Seventeen species of bumble bee (Bombus spp.), honey bee (Apis mellifera) and the leaf cutting bee Megachile periherta were identified as pollinators, with bumble bees being most common (97% of observations) (De Clerck-Floate et al., 1997).

Physiology and Phenology

A study by Alex (1962) found that roots of seedlings penetrated downward ca. 1 cm/day during the first 31 days in fine sandy loam. Thereafter the rate was slower but roots reached a depth of 56 cm after 105 days. The total length of all roots of one 105 day old plant grown in fine sandy loam exceeded 27 m. Adventitious stem buds were present on the primary axis after 22 days of age and on the second and third order branch roots at 105 days of age. Stem buds on branch roots were mostly more than 16 cm distant from the primary axis and at depths of 2 cm to more than 10 cm below the ground surface (Alex, 1962). Once established, seedlings can flower and set seed within the first year (Vujnovic and Wein, 2005).

L. dalmatica has been shown to benefit greatly from enhanced carbon dioxide levels. In one study, at 600 ppm CO2, the biomass of L. dalmatica increased by 13 fold, seed production by 32 fold and clonal expansion by seven fold, much larger than the effects observed on the native C3 grass Pascopyrum smithii [Elymus smithii] (Blumenthal et al., 2013). Increased temperatures of 1.5/3.0°C (day/night) had little effect (Blumenthal et al., 2013). However a study by Dijkstra et al. (2010) found much less pronounced increases and emphasized the potential interactions with nitrogen and water levels.

Longevity

The average life of a plant is about three years. The life of a stand varies and depends on the interactions of the plant's growth habits with environmental factors. A stand may disappear within three years under severe competition. However the development of floral stems from secondary crown points on lateral roots may prolong or sustain the stand beyond the life of the original plants (Robocker, 1974).

Seeds persist in the field for at least 10 years (Robocker, 1974). A study by Bruns (1965) found that seeds could still germinate after 12 months of submergence in canal water.

Nutrition

Nitrogen addition has a strong positive effect on plant performance, with a two fold increase in both biomass and seed production (Jamieson et al., 2010).

Associations

In North America, L. dalmatica is associated with pastures and rangelands dominated by Bromus tectorum, B. japonicus, Stipa comata, Koeleria cristata [Koeleria pyramidata], Festuca idahoensis and Artemisia tridentata (Vujnovic and Wein, 2005).

Environmental Requirements

L. dalmatica is favoured by high water and nitrogen availability, but is relatively unpalatable to cattle. Cover of L. dalmatica was high on steeper slopes, particularly those with southern aspects (Jamieson et al., 2010). The beneficial effects of nitrogen on L. dalmatica can be neutralized by addition of labile carbon to the soil (Blumenthal, 2009).

Wilson et al. (2005) indicate that L. dalmatica is particularly favoured in areas with dry summers. Nevertheless, snow can be highly beneficial to L. dalmatica, apparently in terms of providing high moisture during its establishment phase (Blumenthal et al., 2008).

Post wildfire conditions in high severity burned areas favour increased density, cover, reproduction and spread of L. dalmatica. Whilst native species richness may be reduced, suggesting that the invasive species would persist, at least in the short term, at the expense of natives (Dodge et al., 2008). L. dalmatica was also found to benefit from prescribed fire in a rangeland situation (Jacobs and Sheley, 2003).

Climate

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ClimateStatusDescriptionRemark
BS - Steppe climate Preferred > 430mm and < 860mm annual precipitation
BW - Desert climate Tolerated < 430mm annual precipitation
Cf - Warm temperate climate, wet all year Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Ds - Continental climate with dry summer Preferred Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
35-56 30-50 0 0

Air Temperature

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Parameter Lower limit Upper limit
Mean annual temperature (ºC) -5
Mean minimum temperature of coldest month (ºC) -25

Rainfall

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ParameterLower limitUpper limitDescription
Dry season duration08number of consecutive months with <40 mm rainfall
Mean annual rainfall3001500mm; lower/upper limits

Rainfall Regime

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Summer
Uniform
Winter

Soil Tolerances

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Soil drainage

  • free

Soil reaction

  • acid
  • alkaline
  • neutral

Soil texture

  • heavy
  • light
  • medium

Special soil tolerances

  • shallow

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Brachypterolus pulicarius Herbivore Inflorescence to genus USA and Canada
Calophasia casta Herbivore Leaves not specific
Calophasia lunula Herbivore Leaves not specific USA and Canada
Chrysolina gypsophilae Herbivore to genus
Chrysomela rossia Herbivore not specific
Eteobalea intermediella Herbivore Roots to species USA and Canada
Eteobalea serratella Herbivore Roots to species USA and Canada
Mecinus janthiniformis Herbivore Stems to genus USA and Canada
Mecinus laeviceps Herbivore Stems to genus
Mecinus peterharrisi Herbivore Stems to genus
Rhinusa antirrhini Herbivore Seeds to genus USA and Canada
Rhinusa linariae Herbivore Roots to genus USA and Canada
Rhinusa neta Herbivore Seeds to genus USA and Canada
Rhinusa rara Herbivore Stems to species

Notes on Natural Enemies

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The natural enemies of L. dalmatica have been well studied as a part of efforts to achieve biological control. Potential biocontrol organisms have included Calophasia lunula, Mecinus janthiniformis, Eteobalea intermediaella, Rhinusa neta, R. linariae and R. antirrhini. Recent studies include the stem boring weevils M. laeviceps and M. peterharrisi and the stem-galling weevil R. rara.

Means of Movement and Dispersal

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Natural Dispersal

Seeds of L. dalmatica mainly fall near the parent plant but may also be spread to some extent by wind (Robocker, 1974). L. dalmatica can also reproduce vegetatively by the production of new shoots from roots and root fragments.

Vector Transmission

Some dispersal can occur locally via grazing by cows and deer. It has been suggested that seed can remain viable after ingestion and egestion (Robocker, 1974).

Accidental Introduction

Accidental introduction can occur on a local basis by contaminated cultivation equipment spreading seeds or root fragments.

Intentional Introduction

Intentional introductions have readily happened, as L. dalmatica has been imported into a number of countries for ornamental purposes.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Escape from confinement or garden escape Yes
Garden waste disposal Yes
Horticulture Yes Yes
Ornamental purposes Yes Yes

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Land vehicles Yes
Machinery and equipment Yes
Water Yes
Wind Yes

Impact Summary

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CategoryImpact
Animal/plant collections None
Animal/plant products None
Biodiversity (generally) Negative
Crop production None
Cultural/amenity Positive
Economic/livelihood Negative
Environment (generally) Negative
Fisheries / aquaculture None
Forestry production None
Human health None
Livestock production Negative
Native fauna None
Native flora None
Rare/protected species None
Tourism None
Trade/international relations None
Transport/travel None

Economic Impact

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L. dalmatica asserts an economic impact on productive grassland and rangelands in Canada and the USA. This species becomes dominant as a result of vigorous vegetative growth and competition, especially under conditions of overgrazing and drought, but also perhaps as a result of allelopathy via the action of iridoid glycosides under low nitrogen conditions (Jamieson et al., 2013). Jacobs and Sing (2006) indicate that grass production can be 2.5 times lower in dense infestations of L. dalmatica than in similar areas without the weed. No other quantitative estimates of damage have been seen. It is rarely reported in other crops, except in lucerne/alfalfa (Medicago sativa) and in pine plantations (Pinus species) (Vujnovic and Wein, 2005).

De Clerck-Floate and Turner (2013) refer to its potential toxicity to livestock, though other authors generally suggest that they avoid it. Sing and Peterson (2011) discuss in detail the various metabolites in L. dalmatica and their potential for toxicity to animals. This species can also be a reservoir for crop pathogens including cucumber mosaic virus and it can have a tendency to increase soil erosion. 

Environmental Impact

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Impact on Biodiversity

Although L. dalmatica has become dominant in a range of ecologies in North America, including natural habitats, there have been no reports of the serious effects on biodiversity or individual endangered species. Sing and Peterson (2011) make detailed attempts to quantify the environmental risks from L. dalmatica and the levels of the weed which would cause significant reductions. They concluded that more than six L. dalmatica plants per 10 m2 could cause a 25% reduction in Hedeoma diffusum. A dry weight of 1,163 kg/ha L. dalmatica is the threshold beyond which there could be 25% reduction in cool season grasses.

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Highly adaptable to different environments
  • Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
  • Pioneering in disturbed areas
  • Long lived
  • Fast growing
  • Has high reproductive potential
  • Has propagules that can remain viable for more than one year
  • Reproduces asexually
  • Has high genetic variability
Impact outcomes
  • Ecosystem change/ habitat alteration
  • Host damage
  • Monoculture formation
  • Negatively impacts agriculture
  • Negatively impacts forestry
  • Reduced native biodiversity
  • Threat to/ loss of native species
Impact mechanisms
  • Competition - monopolizing resources
  • Competition - smothering
  • Pest and disease transmission
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Highly likely to be transported internationally deliberately
  • Difficult to identify/detect as a commodity contaminant
  • Difficult/costly to control

Uses

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Economic Value

Due to its showy flowers, L. dalmatica has been widely cultivated as an ornamental in gardens. There is an early record of it being so used in Italy before 1594 and by the nineteenth century it was present in England and by the end of that century in the USA (Vujnovic and Wein, 2005). It is still commercially available as seed or as root pieces in Europe and Asia. Exotic toadflaxes including L. dalmatica also continue to be sold commercially in the USA, although this is illegal in a number of states where they are listed as noxious (Wilson et al., 2005).

Uses List

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Environmental

  • Amenity

General

  • Sociocultural value

Ornamental

  • Propagation material
  • Seed trade

Similarities to Other Species/Conditions

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L. dalmatica is quite distinct from the co-occurring L. vulgaris, which has narrow strap like leaves. L. genistifolia, which also occurs in the USA, also differs from L. dalmatica in its much narrower leaves and relatively small corolla (2-5 cm), while the seeds are without a winged margin.

Prevention and Control

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Prevention

SPS Measures

L. dalmatica is listed as noxious in Arizona, California, Colorado, Idaho, Minnesota, Montana, Nevada, North Dakota, New Mexico, Oregon, south Dakota, Utah, Washington and Wyoming, USA (USDA-NRCS, 2015). In British Colombia, Canada, it is listed as noxious in Alberta and Manitoba (De Clerck-Floate and Turner, 2013).

Control

Cultural Control and Sanitary Measures

It is well recognized that L. dalmatica is quick to exploit gaps and weaknesses in established grass stands. It can be kept out of areas by maintenance of a dense healthy stand. Grasses may vary in their effectiveness and in one study of grasses to suppress L. dalmatica, the greatest reduction (95%) was found with Elymus lanceolatus (Rose et al., 2001). However, once established it may not be readily suppressed by newly sown grasses. Early detection is vital for the control of new infestations.

Physical/Mechanical Control

Mowing is relatively ineffective for controlling L. dalmatica as the weed can readily recover from the root systems and the removal of competition from other vegetation may allow it to increase. Similarly burning may encourage growth rather than suppress it. In crop land intensive cultivation for at least two years with at 8-10 cultivations in the first year may be required. Hand pulling can prevent seeding but only annual grubbing and pulling over a 10-15 year period can control it fully (Vujnovic and Wein, 2005).

Biological Control

L. dalmatica has been the subject of a number of biological control programmes. According to De Clerck-Floate and Turner (2013), five insect biocontrol agents have been tested and intentionally introduced into Canada for control of L. dalmatica. The first field release took place in 1963.

Of the five insects released, three have established on L. dalmatica. These include the seed capsule weevil Rhinusa antirrhini, the defoliating moth Calophasia lunula and the stem boring weevil Mecinus janthiniformis. The latter had previously been referred to as ‘M. janthinus’ but differing results from different populations of this ‘species’ led to the realisation that two species were involved. Only M. janthiniformis is effective on this L. dalmatica while L. janthinus is effective on L. vulgaris (Toševski et al., 2011). Toševski et al. (2013) have now described a fast and accurate way of distinguishing the two Mecinus species haplotypes using PCR-RFLP diagnostic assay of the mitochondrial cytochrome oxidase subunit II (COII) gene.

R. antirrhini has established well in British Colombia, Canada and populations are increasing. It is however uncertain whether this seed feeding agent can have a significant impact on the weed (De Clerck-Floate and Turner, 2013).

In Canada, Calophasia lunula has only become established in southern British Colombia and not at all in Alberta, apparently due to low temperatures (De Clerck-Floate and Turner, 2013). Jamieson et al. (2010) found that C. lunula has a mechanism to de-activate the iridoid glycosides, defence mechanisms, in L. dalmatica but ‘M. janthinus’ does not.

M. janthiniformis is by far the most successful biocontrol agent released in Canada. Damage is caused by both adults and larvae and conspicuous reductions in the weed have been recorded. Results are less successful in Alberta almost certainly due to severe winter temperatures. Some disappointing results may also be due to the wrong Mecinus species being released. Weed and Schwarzländer (2014) suggest that the impact of M. janthiniformis may vary considerably due to site specific variation in rainfall and density dependent processes. As a result alternative control methods should be prioritized in areas where herbivore impact is expected to be low. Studies have recently started on two additional Mecinus species, M. laeviceps and M. peterharrisi (Toševski et al., 2016). A petition for the introduction of the stem-galling weevil R. rara n North America is pending.

Two species introduced but not proving successful are the root galling weevil R. linariae which proved to have a preference for L. vulgaris and is no longer being exploited and the root moth Eteobalea intermediella which established in 1998 but had died out by 2002 and is no longer being used (De Clerck-Floate and Turner., 2013). The related E. serratella was thought by Quarles (2007) to be having an impact on L. dalmatica, but Shelton (2015) notes that L. dalmatica is a relatively poor host for this species and it appears that it is no longer of interest.

Grubb et al. (2002) suggested that the naturally occurring flower feeding beetle Brachypterolus pulicarius might prove to be an important component in the integrated weed management of L. dalmatica but that the adults show a distinct preference for L. vulgaris and its further distribution in North America was not recommended (MacKinnon et al., 2007). The seed capsule weevil R. neta also occurs widely in British Colombia, Canada but is not being actively distributed (De Clerck-Floate and Turner 2013).

Wilson et al. (2005) provide extremely detailed and valuable information on the biology of the biocontrol organisms and the planning, implementation and monitoring of biological control programmes against both L. dalmatica and L. vulgaris.

Chemical Control

Phenoxy-propionic herbicides are superior to phenoxyacetic herbicides in controlling L. dalmatica. Satisfactory control can be obtained with fenoprop. Rates of fenoprop required to check or to control the plant did not injure perennial grasses. Dicamba has also been effective however it is resistant to triclopyr and fluroxypy (Vujnovic and Wein, 2005).

Picloram can be effective when applied at various stages of growth, but granules applied to the soil in the autumn can be more effective than a foliar application at the same rate in spring (Vujnovic and Wein, 2005). A combination of fenoprop and picloram has also provided control (Robocker, 1968).

Aminocyclopyrachlor (140 and 280 g ae ha-1) and aminocyclopyrachlor+chlorsulfuron (140 g/ha+53 g/ha) gave second year control; chlorsulfuron at the dormant stage (105 and 158 g/ha) and aminopyralid at the rosette stage (245 g/ha) also gave 2 years of control. The treatments had only minor effects on grass species (Kyser and DiTomaso, 2013).

Herbicides recommended by USDA Forest Service (2012) for use in non-crop areas include imazapic, glyphosate, rimsulfuron, sulfometuron and chlorsulfuron.

IPM

Quarles (2007) suggests that integrated control of L. dalmatica could involve combinations of clean cultivation, pulling, mowing, burning, grazing, competitive planting, using biological control agents and herbicides. Suggestions for integrated control strategies are also made by the USDA Forest Service (2012). Suggestions include checking hay and straw for the presence of seed, feeding certified weed-free hay pellets to horses, combining control methods and ensuring that follow up treatment is carried out to treat plants that are missed.

Ecosystem Restoration

There are indications that the reduction of L. dalmatica in mixed natural plant communities has tended to encourage the invasion of other equally undesirable weedy species such as Bromus tectorum and Centaurea maculosa [Centaurea podospermifolia].

References

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Links to Websites

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WebsiteURLComment
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gatewayhttps://doi.org/10.5061/dryad.m93f6Data source for updated system data added to species habitat list.

Contributors

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13/12/2016 Updated by:

André Gassmann, CABI-CH, Switzerland

12/06/2015 Original text by:

Chris Parker, Consultant, UK

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