Yellow Toadflax

Linaria vulgaris

WA C Plantaginaceae
Data Maturity Baseline

Washington State Classification

Class C — Widespread, County-Selected Control

Yellow toadflax can invade rangeland and cultivated fields and compete with desirable plants and reduce their yield.

Quick Reference

Type
perennial herb
Origin
Europe and Asia

Identification

Growth Habit

Perennial that grows 8 to 31 inches tall from creeping roots, often forming colonies. Plants are light green and have yellow flowers with orange throats and bloom during the summer (June to September). It has a bad smell.

Leaves

Leaves are alternately arranged and numerous along the stem. Each leaf is very narrow (linear) and up to 3.9 inches (10 cm) long. They are hairless and have pointed tips.

Flowers

Flowers are crowded onto the top 2 to 9 inches of the plant stem. They are yellow with hairy, orange throats. They resemble snapdragons, each having a spur-like appendage at the base.

Fruit & Seeds

Flowers form a cylindrical capsule that is about .4 inches long. Seeds are dark in color, brown to black, and are flattened, having a papery wing.

Impact

Yellow toadflax can invade rangeland and cultivated fields and compete with desirable plants and reduce their yield. It is seldom eaten by livestock.

Ecology & Spread

Habitat

Yellow toadflax is found in a variety of habitats including roadsides, edges of fields, rangelands, meadows, cultivated fields and wastelands. Please click here to see a county level distribution map of yellow toadflax in Washington.

Spread Mechanisms

seed

Reproduction

Yellow toadflax can reproduce by seeds and by its horizontal rootstalks which send up new shoots.

Regional Notes — Puget Sound

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Control Methods

Mechanical

  • Cultivation of infested fields should begin in early summer and be repeated every 21 days. One year of thorough cultivation (8 or more times over) will eliminate a high percentage.

Biological Control

  • The toadflax flower-feeding beetle, Brachypterolus pulcarius, larvae feed on the reproductive structures within the flowers, including the seeds, and adults feed on young plant stems. The toadflax seed capsule weevil, Rhinusa antirrhini (formerly Gymnetron), larvae feed on immature seeds and adults feed on flowers and young shoots. For more information about biological control of yellow toadflax, please visit WSU Extension Integrated Weed Control Project.