Yellow toadflax

Yellow Toadflax (Linaria vulgaris)

Report

Credit: Caleb Slemmons, National Ecological Observatory Network, Bugwood.org

Management Category

Synonyms

Common toadflax
Butter and eggs
Wild snapdragon

ID Characteristics

General: A herbaceous perennial, the yellow toadflax is part of the Plantaginaceae family and is listed as provincially noxious in the Weed Control Act.

Flowers: Yellow toadflax has bright yellow flowers that resemble snapdragons. The yellow flowers have an orange throat, are 2 – 3.5 cm long, and arranged in groups (called racemes) at the ends of each branch.

Stems: Smooth, erect, unbranched, and light green stems that grow between 0.15 – 1.0 m tall. Mature plants can have as many as 25 stems.

Leaves: Soft, lance-shaped and light green, the leaves grow up to 10 cm in length in an alternate pattern along the stem.

Seeds: Brown or black circular seeds, surrounded by a notched wing.

Fruit: In the form of seed capsules, the fruit are egg-shaped, between 5 – 10 mm long, and 2-celled with wings around 2 mm wide.

Roots: A taproot growing up to 1 m into the soil. This taproot has long, lateral roots that develop adventitious buds, which produce new plants.

Similar Species

Invasive

Dalmatian toadflax (Linaria dalmatica) has a shorter, wider, and broader base than the yellow toadflax.

Dalmatian toadflax (credit: SSISC)

Leafy spurge (Euphorbia esula) has similar leaves and stems to yellow toadflax; however, this species produces a milky latex, which yellow toadflax lacks.

Leafy spurge (credit: SSISC)

Habitat and Origin

Yellow toadflax was introduced from Europe and Asia as an ornamental garden plant. It was also used to make dyes and folk remedies.

Yellow toadflax can be found in well-drained, open, low-elevation forests and grasslands. It is most commonly found in coarse-textured soil on roadsides, railroads, gravel pits, cultivated fields, and clear-cuts.

How it Spreads

Yellow toadflax is a perennial forb that reproduces both by seed and vegetatively through root segments. A mature plant can produce up to 30,000 seeds annually, and they can remain viable in the soil for up to ten years. Root fragments as short as 1 cm can grow into a full plant the following year.

Impacts

Ecological:

Outcompetes native habitats.
Reduces biodiversity.

Economic:

Yellow toadflax is an alternate host for plant diseases like cucumber mosaic virus and broad bean wilt virus. Its presence could put other more valuable plants at risk.
Reduce forage for grazers.

Health:

Toxic to humans and animals.

Prevent the Spread

Yellow toadflax is found in the Sea to Sky region and its distribution is beyond landscape-level control. When yellow toadflax is present at high-priority locations and negatively impacting them, their control is considered a high priority.

Otherwise, the goal is to prevent it from spreading to new (uninfested) areas, and to control it where possible to limit its impact on biodiversity.

Learn to identify yellow toadflax: Use the images presented on this profile page.

What to do if you spot it: You can report any yellow toadflax sighting by visiting our reporting page.

DO:

Regularly monitor properties for weed infestations.
Ensure soil and gravel is uncontaminated before transport.
Quickly re-vegetate disturbed areas with fast-growing competitive, native plants can limit growth of Scotch Broom and is a fundamental tool to limit its spread.
Minimize soil disturbance in area surrounding infestation.
Ensure plants (particularly flowering heads or root fragments) are bagged or covered to prevent spread during transport to designated disposal sites (e.g. landfill).

DO NOT:

Plant yellow toadflax in a garden, no matter how well-contained its enclosure may seem.
Move soil that has been contaminated with yellow toadflax
Unload, park, or store equipment or vehicles in infested areas; remove plant material from any equipment, vehicles, or clothing used in such areas and wash equipment and vehicles at designated cleaning sites before leaving infested areas.
Mow or weed-whack yellow toadflax plants, as the fragments can propagate as new colonies. Frequent mowing may also accelerate shoot development, leading plants to spread laterally from the parent plant.
Compost yellow toadflax, especially the seeds!

Control

Cultural Control:

Seeding disturbed areas with perennial grasses and forbs will provide ground cover and competition.

Mechanical Control:

Hand-pulling is effective, especially in coarse-textured soils where roots can be removed easily (plants will regrow if root mass remains in the soil).
Cutting, mowing or burning is not recommended because it can stimulate the plant’s growth.
Any plant material that is removed should be disposed of at the landfill.

Chemical Control:

Yellow toadflax is difficult to manage with herbicides. Herbicides should be applied before flowering, when root carbohydrate reserves are at their lowest.
Dicamba and picloram (with or without 2,4-D) have been effective in some situations; however, picloram is not suitable for wet, coastal soils.
We recommend that any herbicide application be carried out by a person holding a valid BC Pesticide Applicator Certificate. Before selecting and applying herbicides, you must review and follow herbicide labels and application rates; municipal, regional, provincial and federal laws and regulations; species-specific treatment recommendations, and site-specific goals and objectives.

Biological Control:

Several beetles, weevils, and moths can be used to control yellow toadflax, including the seed-feeding beetle (Brachypterolus pulicarius), foliar-feeding moth (Calophasia lunula), and stem-mining weevil (Mecinus janthinus).