Linaria vulgaris
Figwort family (Scrophulariaceae)

Description: This perennial plant is 1-2' tall and little branched. The alternate leaves are densely distributed all around the central stem, appearing to be opposite or whorled; they very little in length. The leaves are up to 2" long and 1/6" across, bluish or grayish green, linear with smooth margins, and hairless. Each leaf tapers to a petiole-like base and is sessile. The central stem has a few hairs near its apex, but becomes glabrous or slightly woody near its base. This stem terminates in a spike-like raceme of flowers that is several inches long. The flowers are distributed all around this raceme. Each flower is about 1" long and consists of a tubular corolla with an upper and lower lip that is pale yellow; there is also a long nectar spur at the end of the corolla that hangs downward. The upper lip is divided into 2 lobes that are folded upward, while the lower lip consists of 2 lobes that fold downward and an orange-yellow palate that obstructs the opening to the throat of the corolla. At the base of the flower, there is a small green calyx with 5 teeth and a short pedicel. Usually the underside of the corolla is cream-colored, in contrast to the bright orange-yellow of the palate. The blooming period occurs from early to mid-summer for about a month, and intermittently thereafter until the early fall. Some colonies of plants bloom later than others. Many plants in a colony may fail to bloom. Each flower is replaced by a seed capsule that contains numerous small seeds. Each seed is brown and flattened; it is surrounded by a rather large papery wing with a small notch on one side. Assisted by their papery wings, these seeds are blown about by the wind. The root system consists of a long taproot and shallow rhizomes that spread in all directions. This plant usually forms clonal colonies by means of its rhizomes.

Cultivation: The preference is full sun, dry conditions, and a barren soil that is gravelly or sandy. Under these conditions, this plant can spread aggressively because of the reduced competition from taller plants with wider leaves. Soil with a high pH is readily tolerated.

Range & Habitat: The non-native Butter-and-Eggs is a common plant in central and northern Illinois, but it is less common or absent in southern Illinois, particularly in the SE section of the state (see Distribution Map). This wildflower was introduced into North America from Eurasia (where it is native to the Mediterranean region) as an ornamental plant, and it is still offered for sale by the horticulture industry. Habitats include pastures, old fields, gravelly or sandy areas along railroads and roadsides, gardens, and sterile waste ground. This plant is typically found in disturbed areas, particularly along railroads, although it is aggressive enough to invade dry sand prairies and gravel prairies. Occasional wildfires and mowing are not effective in controlling this plant. Butter-and-Eggs is more invasive in the drier western areas of the United States.

Faunal Associations: The flowers are pollinated by bumblebees, which are strong enough to push past the palate to enter the throat of the corolla. Other floral visitors include other long-tongued bees, butterflies, and skippers. According to Robertson (1929), the butterflies and skippers are not effective pollinators of the flowers, however. Several insect species have been introduced to control the spread of Butter-and-Eggs. This includes Brachypterolus pulicarius, a small black beetle that feeds on the tips of the shoots; Gymnaetron antirrhini, a weevil that feeds on the seed capsules; and Calophasia lunula (Toadflax Brocade), a moth with larvae that feed on the foliage and flowers. The foliage is not a preferred source of food among mammalian herbivores and it is rarely eaten; it contains a glycoside that is mildly toxic to cattle.

Photographic Location: A gravelly area along a railroad in Urbana, Illinois, where a colony of plants occurred.

Comments: Butter-and-Eggs is another garden plant that has escaped into the wild to become a permanent resident. It has spread to all areas of the United States. The large and showy flowers resemble those of Antirrhinum majus, the cultivated Snapdragon of modern horticulture, although this latter species rarely escapes from cultivation. Another species, the introduced Linaria genistifolia dalmatica (Dalmatian Toadflax), is an uncommon plant that occurs in a few counties of northern Illinois. This latter species resembles Butter-and-Eggs somewhat, but its flowers are larger in size (about 1" long) and the palate of its flowers is yellow, rather than orange-yellow. The leaves of Dalmatian Toadflax are much broader than those of Butter-and-Eggs, and they clasp the stem. The native Linaria spp. in Illinois are annual or biennials with smaller blue flowers. Another common name for Linaria vulgaris is Yellow Toadflax.