Borage family (Boraginaceae)
Description: This adventive plant is a winter annual or biennial about ½–2' tall, branching very little except at the base. The round stems are more or less hairy. The alternate leaves are up to 1½" long and ¼" across. They are oblanceolate, lanceolate-oblong, or oblong-linear, and sessile at the base. The upper surface of each leaf has a single central vein, but radiating side veins are not visible. The leaves are more or less pubescent, although they occasionally have longer white hairs. Their margins are smooth and ciliate.
The nearly sessile flowers develop from the axils of the leaves in the upper portion of the stems. They are bunched together while in bloom or at the bud stage, but become more separated from each other as the flowering stems continue to elongate. Each flower is about ¼" long, consisting of a tubular white corolla with 5 small lobes and a hairy green calyx with 5 teeth that are linear-lanceolate. These teeth are about as long as the corolla. There are 5 stamens and a pistil that are inserted within the narrow throat of the corolla. The blooming period can occur from mid-spring to mid-summer and lasts about 2 months. Each flower is replaced by 4 nutlets. A nutlet is truncate at the base and tapers to a blunt round tip at the top. It is broadest a little below the middle, and has a greyish brown surface that is rough and wrinkled. The root system consists of a taproot. This plant spreads by reseeding itself.
Cultivation: This adaptable plant can be found in full or partial sun and mesic conditions in fertile loam, clay-loam, or sandy soil. Open areas are preferred where there is a scarcity of taller plants.
Range & Habitat: Corn Gromwell is occasional to locally common in most areas of Illinois, except in the NW and SE, where it is uncommon or absent (see Distribution Map). It is adventive from Eurasia. Habitats include cropland consisting of winter wheat or rye, fallow fields, vacant lots, grassy areas along roadsides and railroads, and miscellaneous waste areas. This weed occurs primarily in fields or along railroads, but it also appears in run-down areas of cities. Corn Gromwell prefers disturbed areas, and doesn't invade high quality natural sites to any significant degree.
Faunal Associations: Little information is available about floral-faunal relations for this species. According to Muller of 19th century Germany, the flowers of Corn Gromwell have few insect visitors. Occasionally, they attracted White butterflies, bees, and Syrphid flies.
Photographic Location: A grassy vacant lot in Urbana, Illinois.
Comments: This is a rather inconspicuous plant even while it is blooming. Corn Gromwell resembles many other weeds with small white flowers, but it has a distinguishing characteristic that sets it apart: The teeth of the hairy calyx are unusually long, slender, and conspicuous – about the same length as the flowers. Long after the corolla of a flower has withered away, the teeth of the calyx surround the nutlets on all sides and are much taller than them. Corn Gromwell resembles other members of the Borage family to some extent, including the native Lithospermum latifolium (American Gromwell) and introduced Lithospermum officinale (European Gromwell). However, these latter species have wider leaves with conspicuous side veins. Corn Gromwell is easily distinguished from the many weedy members of the Mustard family because its tubular flowers have 5 petal-like lobes, while the flowers of the latter have only 4 petals. An obsolete scientific name for this plant is Lithospermum arvense.