Weed(s) Of The Week #10 Dalmatian Toadflax (Linaria dalmatica)
Weed(s) Of The Week #10
Dalmatian Toadflax (Linaria dalmatica)
Common Toadflax AKA Yellow Toadflax (Linaria vulgaris)
Both Species Noxious Under Alberta’s Weed Control Act
Submitted By Kelly Cooley, CoolPro Solutions
Both of the Toadflax species are creeping rooted perennial invasives that many mistakenly call ‘wild snapdragons’.
Dalmatian Toadflax emerges earlier (May) and flowers in late June - early July here in southwest Alberta. It is generally taller (1 to 5 feet or .3 to 1.5 metres), and has waxy, broader, stem clasping leaves compared with Common Toadflax's narrower, longer, pointed, non-waxy leaves. Dalmatian Toadflax prefers open or lightly vegetated spots in drier gravel, rocky, sand, or silt textured soils, with neutral to slightly alkaline pH, on roadsides, pastures, riparian areas, grasslands, forest clearings, and disturbed areas. Dalmatian Toadflax is generally not a problem in cultivated cropland or forages.
Common Toadflax emerges later (June) and flowers in late July – early August here in southwest Alberta. It is generally shorter (1 to 3 feet or 300 to 900 cm), and has narrower, longer, pointed, non-waxy leaves compared with Dalmatian Toadflax's waxy, broader, stem clasping leaves. A much more adaptable invader, Common Toadflax invades roadsides, pastures, riparian areas, grasslands, forest clearings, and disturbed or cultivated areas. Common Toadflax prefers more moist, fertile soils than Dalmatian Toadflax, but can tolerate all soil types. Common Toadflax may invade and spread in contaminated forage crops.
Both species are capable of forming dense colonies made up of a network of both flowering and non-flowering shoots that spread mainly through a network of vertical and horizontal budded creeping roots. Seeds are a secondary form of reproduction. Seeds and/or even small fragments of the creeping root system with viable buds still intact can also be spread in infested soil and gravel, or on the equipment that works in these soil/gravel areas.
Control of both species can be very difficult, and may take many years for established patches. Efforts should be directed at minimizing the amount of above-ground growth by pulling, cutting, or top-growth herbicide suppression of the shoots and leaves throughout the growing season. This both limits flowering and also forces the creeping root systems to continually regenerate shoots and leaves. Best results with selective broad-leaf herbicides are found in the fall, and are even more effective if the plants are prevented from flowering throughout the growing season as described above.
Both species of Toadflax are susceptible to biological control through two distinct species of stem-mining weevil in the genus Mecinus that have been approved and released through Agriculture & Agri-Food Canada’s biological control research scientists based in Lethbridge. These insect bioagent releases are assisted financially and through distribution by the Alberta Invasive Species Council and rural municipalities here in Southern Alberta, including the MD of Pincher Creek. These weevils can be slow to establish over several seasons, but once the populations settle in, they quite effectively reduce the prevalence of both species of Toadflax, which we have witnessed at local release sites for these biological control agents.
More information can be found in the fact sheets available from the Alberta Invasive Species Council on their website (see links in comments below), and you can report this invader yourself using their free EDDMapS application on your mobile device. For local control options for both Dalmatian and Common Toadflax, please contact our Agricultural Fieldman at 403-339-8741.
Dalmatian Toadflax Fact Sheet:
https://secureservercdn.net/198.71.233.231/yjc.cc8.myftpupload.com/wp-content/uploads/2020/07/N_FS-DalmatianToadflax.pdf?time=1626373747
Common Toadflax Fact Sheet:
https://secureservercdn.net/198.71.233.231/yjc.cc8.myftpupload.com/wp-content/uploads/2020/07/N_FS-CommonToadflax.pdf?time=1626373747
Photo Credits:
Kelly Cooley, CoolPro Solutions
Teton County, Wyoming
Michael Shephard, USDA Forest Service
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