Dalmatian toadflax, Linaria dalmatica (L.) Mill. (Scrophulariaceae), is a plant native from central Europe east to central Asia. Dalmatian toadflax was originally introduced into North America as an ornamental plant, beginning in the late 1800's. By the 1920's, L. dalmatica populations had escaped from cultivation and become weedy; presently, Dalmatian toadflax is found in at least 22 US states and seven Canadian provinces, but it is most widely distributed in the western US and Canada.

Linaria dalmatica is a short-lived perennial with a taproot that may extend 1 m or more into the soil. Most aboveground growth dies back in the fall, with the exception of short, prostrate stems that persist through the winter. In spring, erect shoots begin growth from root buds, reaching a height of 0.4 to 1.0 m; a single plant may produce 10 or more stems.

Flowers are bright yellow with orange markings and elongate spurs and occur in simple racemes on the stems. Flowering occurs from mid-summer to early fall. Flowers are pollinated by insects producing capsules containing 100-200 seeds. A single plant may produce several hundred thousand seeds. Dalmatian toadflax also reproduces vegetatively, from adventitious buds originating on horizontal roots.

Dalmatian toadflax is typically found along roadsides or railroads and in idle cropland, pastures, and rangelands, usually on comparatively dry sites with coarse, well-drained soils. Because seedlings are relatively poor competitors for soil moisture, establishment is favored by soil disturbances, such as road construction, or by overgrazing. Once established, however, Dalmatian toadflax may become an effective competitor, reducing the abundance of grasses and other forbs. In addition, Dalmatian toadflax contains alkaloids that may be deleterious to grazing mammals, though livestock and wildlife species rarely consume the weed. Thus, the primary economic impact of L. dalmatica lies in reduced livestock production on infested pastures and rangeland.