Gentian family (Gentianaceae)
Description: This perennial plant is ½–2' tall, and is unbranched. The light green or reddish central stem is slender and smooth. The opposite leaves are narrowly ovate to elliptic and sessile. They have smooth margins, a prominent central vein, and are hairless. The leaves are up to 3½" long and 1½" across; their upper surfaces are medium to dark green and shiny.
In the upper part of the plant, 1-6 flowers develop from axils of the opposite leaves, with a greater number of flowers at the apex. These tubular flowers are pale blue to blue-violet, often with vertical streaks of purple, green, or white. They are about 1½" long and closed at the top (or nearly so). Each flower has five lobes, with each adjacent pair of lobes connected together by a lighter colored membrane. This membrane is the same length or slightly lower than the adjacent lobes, with an irregular pattern at the top; it is not readily perceptible unless the lobes of the flower are spread apart. Underneath the flowers, the lanceolate lobes of the calyx are erect, spreading only slightly outward; they are not recurved. The blooming period is late summer to fall, and lasts about a month. There is no noticeable fragrance to the flowers. The seed capsules split into 2 sections, releasing numerous small seeds that can be dispersed by wind or water. The root system consists of a long stout taproot.
Cultivation: The preference is full or partial sun, and moist to mesic soil. This gentian often grows in sandy soil, but will tolerate other kinds of soil, including fertile loam. Foliar disease is not a significant problem, although the leaves sometimes turn yellow in response to strong sunlight and dry weather. It is faster and easier to introduce gentians as transplants, rather them to start them by seed, which is difficult and slow.
Range & Habitat: The native Soapwort Gentian is an uncommon plant that occurs in NE Illinois and a few counties in southern Illinois (see Distribution Map). It can occur in other localities as a result of restoration activities, or as an escape from cultivation. Habitats include moist to mesic sandy Black Oak forests, sandy savannas, sand prairies, and sandy thickets. Less often, this gentian can be found in non-sandy habitats that are similar to those already mentioned. This conservative plant is rarely found in disturbed areas.
Faunal Associations: Bumblebees are the primary pollinators; they are strong enough to force their way into the flowers, where they suck nectar. Sometimes tiny beetles sneak into the flowers to feed on the pollen, while some larger beetles, such as Epicauta pensylvanica (Black Blister Beetle), may knaw on the flowers themselves. The seeds are too small to be of any interest to birds, while the bitter foliage is too bitter deters most herbivores; however, deer sometimes chomp off the tops of the plants.
Photographic Location: The photographs were taken at Hooper Branch Savanna Nature Preserve in Iroquois County, Illinois. This plant was growing in a moist sand prairie.
Comments: Soapwort Gentian usually has pale to medium blue flowers, while Gentiana andrewsii (Bottle Gentian) often has deep blue flowers. Color alone, however, is not a reliable guide to species identification. The calyx lobes in flowers of Soapwort Gentian are fairly straight and upright, while the calyx lobes of Bottle Gentian often curl outward. In the flowers of Soapwort Gentian, the connecting membranes are a little lower than, or equal to, the lobes of the corolla, while they are higher than the lobes in the flowers of Bottle Gentian. There is also a tendency for Soapwort Gentian to have more slender leaves and stems than Bottle Gentian, but this distinction is not always reliable. Soapwort Gentian differs from Gentiana alba (Cream Gentian) with its bluer, less open flowers and sessile leaves, whereas the leaves of the latter strongly clasp the stem.