Yellow toadflax (Linaria vulgaris L.)
Yellow toadflax was originally introduced as an ornamental plant but has since escaped cultivation and is now listed as a noxious weed in Wyoming. It is often called “snapdragon” or “butter and eggs” because of its distinctive yellow flowers with two lips and a long spur. Yellow toadflax can be distinguished from Dalmatian toadflax by its numerous narrow, linear leaves that appear even in the rosette stage.
Yellow toadflax is an herbaceous perennial in the Plantaginaceae (plantain) family, formerly classified in the Scrophulariaceae family. It typically produces erect stems that grow 1-2 feet tall, although they may occasionally reach 3 feet. Stems are slightly woody near the base and become waxy and herbaceous toward the top. Leaves and upper stems range from blue-green to green in color. The leaves are narrow, linear, waxy, and have smooth margins. They are arranged alternately along the stem and clasp it closely. When crushed, the vegetation emits a distinct musky odor.
Yellow toadflax flowers from early summer through fall. The flowers resemble snapdragons and grow in dense racemes at the ends of stems. Each flower is bright yellow, about 1 inch long, and has two lips—an upper and lower lip—with a prominent orange, bearded throat that is often visible from a distance, giving rise to the common name “butter and eggs.” A long spur extends from the base of each flower. Yellow toadflax spreads through an extensive root system made up of creeping lateral rhizomes. Seeds are produced in capsules and are small, flat, dark brown, and winged.
Yellow toadflax contains quinazoline alkaloids and may be toxic to livestock; however, it is typically avoided by cattle and horses. Sheep and goats have been known to graze the plant without apparent harmful effects.
Quick ID Guide
Life cycle:
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Perennial forb
Height:
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Usually 1–2 feet tall, occasionally up to 3 feet.
Leaves:
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Long, narrow, and linear
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Blue-green to green in color
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Smooth margins and waxy texture
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Alternate along the stem and clasp it
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Numerous leaves are present even in the rosette stage
Flowers:
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Bright yellow snapdragon-like flowers
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Two “lips” with an orange throat
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A long spur extending from the back of the flower
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Grow in dense clusters at the end of stems
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Bloom from early summer through fall
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Often called “butter and eggs.”
Roots:
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Extensive root system with creeping lateral rhizomes
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Spreads aggressively underground and forms dense patches
Reproduction:
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Spreads by both seed and underground rhizomes
Similar Species:
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Dalmatian toadflax: has broad, heart-shaped leaves instead of narrow leaves.
Management Options
Prevention and cultural control methods should be implemented whenever possible to limit the spread of yellow toadflax.
Hand-pulling or digging can be effective for small infestations if performed before the plant becomes well established. Care must be taken to remove the entire root system, including all lateral rhizomes, to prevent regrowth. Tillage may provide control, but it must be repeated every 7 to 10 days for multiple years to exhaust the root reserves. Mowing is not recommended because it stimulates additional root and rhizome growth. Grazing is generally ineffective since livestock do not preferentially feed on yellow toadflax, which may reduce competition from desirable vegetation.
Large infestations may require herbicide treatment. Applications made in the spring can help prevent flowering and seed production, while fall treatments may be more effective at targeting the root system. Always read and follow herbicide label directions before application. Contact Sublette County Weed & Pest for assistance with product selection, application rates, and treatment timing.
