Dalmatian Toadflax

Identification & Biology
Latin Name : Linaria dalmatica
Category : Terrestrial Plants
Description :
  • Creeping-rooted perennial
  • Grows from 0.5 to 1.2 m tall
  • Bright yellow “snapdragon-like” flowers
  • Leaves are waxy, light green and heart-shaped

Toadflax plants begin emerging in the early spring, with flowering occurring from May-August. Individual plants can live up to five years. A mature plant can produce up to 500,000 seeds annually, and the seeds can remain viable for up to 10 years. Prostrate stems emerge in September; they are tolerant of freezing and are associated with floral stem production in the following year. Root buds can form on fragments as short as 1 cm in length and as early as 2-3 weeks after germination. These buds can grow their own root and shoot systems, and become independent plants the next year.

Dalmatian toadflax can sometimes be confused with yellow toadflax (L. vulgaris). Yellow toadflax grows only to 0.6m tall and has leaves that are long, narrow and pointed at both ends.

Look Alikes
Habitat

In British Columbia, Dalmatian toadflax occurs most frequently in the Southern Interior invading open, low-elevation, coniferous forests and adjacent shrub-steppe habitat. It is most commonly found on sandy or gravely soil on roadsides, railroads, pastures, cultivated fields, rangelands and clear cuts. While toadflax can rapidly colonize disturbed or cultivated ground, plants can also invade healthy native plant communities.

Impact & Risks
  • Toadflax displaces native vegetation; it is particularly competitive with winter annuals and shallow-rooted perennials.
  • It can reduce forage production for livestock and other ungulates.
  • Some researchers claim that Dalmatian Toadflax is toxic to livestock when consumed in significant amounts (reports of livestock poisonings are rare).
Prevention & Mitigation
  • Immediately re-vegetate disturbed, bare soils with a suitable seed mix that provides dense, early colonization to prevent weed invasion.
  • Regularly patrol your property for Dalmatian toadflax plants and immediately treat new patches.
  • Cooperate with adjacent landowners and encourage them to control Dalmatian toadflax.
  • Clean vehicles and machinery of plant material and soil before leaving a toadflax infestation.
  • Follow a well-designed grazing plan; excessive livestock grazing reduces competition and favours invasive plants.
Treatment & Disposal
  • Hand pulling is most successful where soils are sandy and/or moist, allowing for removal of as much root as possible.
  • Hand-cutting to ground level in spring or early summer can eliminate seed production and dispersal.
  • Mowing is less effective because it leaves several cm of stem above the soil surface that may allow plants to re-sprout more rapidly.
  • Physical removal must be repeated annually for at least ten years to completely deplete the seed bank.
  • Before applying herbicides, read the label for full use and precautionary instructions. For further information on the selection and application of chemicals to protect your crop, contact AgriService BC at 1-888-221-7141 or email AgriServiceBC@gov.bc.ca
  • Mecinus janthiniformis is a weevil that has been used in the Okanagan Valley to treat Dalmatian Toadflax.
  • Other bioagents include: Calaphasia lunula and Rhinusa antirrhini.
Okanagan Distribution

Priority Level Definitions

Watch For - Poses a significant threat (very high risk) and does NOT presently occur in the region OR is relatively new to the region and is very limited in extent.
High - High risk/impact; limited population with significant potential to spread in the region.
Medium - Medium risk/impact; limited distribution – broader population distribution with potential to spread further in a region.
Low - Low risk/impact; may be widespread or not, may be of concern in specific situations with certain high values – e.g. specific agriculture crops. Some species may be treated primarily with biological control agents.