Linaria vulgaris (Yellow Toadflax)

Linaria vulgaris (Yellow Toadflax) is an upright perennial producing masses of bright yellow to creamy yellow, snapdragon-like flowers from late spring until the first frosts. The flowers are borne in dense terminal clusters on stiff stems lined with narrow, pale green leaves. Each blossom features a distinctive orange patch on the lower lip and a slender spur at the back.

The flowers attract bees, butterflies, and other pollinating insects. Yellow Toadflax is also a larval host plant for the Common Buckeye butterfly (Junonia coenia), whose caterpillars may feed on its foliage.

After flowering, the plant produces rounded seed capsules containing numerous small, dark seeds that can be dispersed by wind, water, animals, and human activity. Yellow Toadflax also spreads vigorously by creeping underground roots. A single plant can develop an extensive root system and produce new shoots some distance from the parent plant, making established colonies difficult to control.

Although attractive in bloom and useful to some pollinators and butterfly larvae, Yellow Toadflax is considered invasive in many parts of North America and is listed as a noxious weed in several western U.S. states and Canadian provinces. It should therefore be grown with considerable caution and avoided where it is invasive or regulated.

• Grows up to 2 ft. tall (60 cm).
• Thrives in full sun in moderately fertile, light, well-drained soil. It performs particularly well in sandy or gravelly soils.
• Once established, it can spread rapidly by seed and underground roots.
• Cutting plants back before seeds mature can reduce self-seeding, but it will not prevent spread by the root system.
• Keep an eye out for aphids and powdery mildew. Yellow Toadflax is generally deer-resistant.
• Propagate by seed in pots in a cold frame in early spring, or by division or softwood cuttings in spring. In regions where the species is invasive or regulated, propagation is not recommended.
• Native to Europe and western Asia.
• Find where this species is invasive in the United States.