Polygala cruciata aquilonia
Milkwort family (Polygalaceae)
Description: This annual plant is 4-12" tall and usually unbranched. The central stem is angular and hairless. The leaves occur in whorls of 4 and are sessile against the stem. They are up to 1½" long and 1/3" (8 mm.) across, linear or linear-oblong in shape, with smooth margins. The central stem terminates in a dense spike of flowers up to 2-3" long and 1" across. These flowers are variable in color, ranging from purplish pink or pink to greenish white. Each flower is about 1/3" (8 mm.) across, consisting of 2 large sepals (called 'wings'), 3 tiny sepals, and 3 petals that form a narrow tube with a crest at its apex. The wings are the most conspicuous part of the flower and determine its color. They are broadly triangular (or deltoid) in shape, and lie to the right and left of the tubular petals. These wings persist on the spike long after the petals have fallen off, and have the appearance of sharp-pointed bracts. The narrow tubular petals are observable near the apex of the spike. They are usually some shade of pink, but quickly fade to brownish yellow, before falling off the spike. The blooming period occurs from mid-summer to early fall, and lasts about 1-2 months. When fertilization occurs, each flower is replaced by a 2-seeded capsule. The seeds are hairy. The root system consists of a taproot. This plant spreads by reseeding itself.
Cultivation: The preference is full or partial sun, and moist sandy soil. The pH should be somewhat acid. This plant can withstand occasional flooding if it is temporary.
Range & Habitat: Cross-Leaved Milkwort occurs primarily in NE Illinois (see Distribution Map). It is an uncommon plant and native to Illinois. Habitats include moist sand prairies, shrub prairies, sandy Black Oak savannas, and edges of sandy marshes. It also occurs along paths in these areas, preferring the reduced competition from taller plants.
Faunal Associations: Probably small to medium-sized long-tongued and short-tongued bees visit the flowers for nectar. Little information is available about this plant's value as a food source to birds or mammals.
Photographic Location: Along a path in the Hooper Branch Savanna Nature Preserve in Iroquois County, Illinois, where Cross-Leaved Milkwort occurred in a moist sand prairie that was somewhat shrubby and sunny moist areas of Black Oak Savanna. This area was prone to occasional flooding from heavy rains.
Comments: The thick spike of flowers of this odd little plant is very conspicuous and easy to spot. Cross-Leaved Milkwort is relatively easy to identify because of the bract-like wings that spread horizontally (left and right) from the center of each flower. In other species of Milkwort, these wings are held upright and resemble petals. The whorled leaves are another distinctive feature, as many species of Milkwort have alternate leaves. Another common name for this plant is 'Drumheads,' which refers to the shape of the stout spike of flowers. Different varieties of Cross-Leaved Milkwort have been described, but only Polygala cruciata aquilonia is known to occur in Illinois.