Description: This introduced 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 are up to 2½" long and 1/6" across, pale or greyish 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 the base. This stem terminates in a spike-like
raceme of flowers that is several inches long. The flowers are densely
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 more or less 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 the
underside of the corolla is cream or pale yellow, 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. 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 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. A soil with a
high pH is tolerated.
Range &
Habitat: Butter-and-Eggs is a common plant in central and northern
Illinois, but less common or absent in southern Illinois (particularly in the
SE area of the state). It was introduced from Eurasia (probably the
Mediterranean region) as an ornamental plant, and 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 areas of sand or
gravel prairies. Wildfires and occasional mowing are not effective in
controlling this plant. Butter-and-Eggs is more invasive in the drier Western
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 insect visitors of the flowers
include other long-tongued bees, butterflies, and skippers. 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, a moth with larvae that feed
on the foliage and flowers. The foliage is not a preferred source of food to
mammalian herbivores and 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. The foliage of Butter-and-Eggs can be
observed in the background of the photograph.
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.
This latter species rarely escapes from cultivation. The introduced Linaria
genistifolia dalmatica (Dalmatian Toadflax) is an uncommon plant that
occurs in a few counties in Northern Illinois. This latter species resembles
Butter-and-Eggs somewhat, but its flowers are larger in size (about 1½"
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. are annual or biennials
with smaller blue flowers. Another common name for Linaria vulgaris is
Yellow Toadflax.