Rare Species Guide

  Basis for Listing

Gentiana affinis var. affinis (pleated gentian) is primarily a cordilleran (western mountains) species that barely reaches the western border of Minnesota. It is limited to prairie remnants in a relatively small portion of the state, and within prairies, it is further restricted to small microhabitats associated with saline wetlands. The ecological and environmental factors that maintain these microhabitats are not well understood. Clearly, these wetlands are vulnerable to a variety of agricultural activities, but other threats have not been studied carefully. Gentiana affinis var. affinis was listed as a special concern species in Minnesota in 1984.

  Description

Gentiana affinis var. affinis is a perennial forb with stems 20-40 cm (7.9-15.7 in.) tall. The leaves are sessile, oblong to ovate in shape, 2-7 cm (0.8-2.8 in.) long and 0.5-2 cm (0.3-0.8 in.) wide, and the margins are minutely scabrous. The flowers are bright blue and have 5 petals; they are 2.5-4 cm (1.0-1.6 in.) long and clustered at the base of the upper leaves. The petals of the elongate, funnel-shaped corolla are united for most of their length by plaited or folded membranes, with the free triangular portion of each petal curving outward from the mouth of the corolla tube. The small, sharply pointed ends of the pleats in the sinuses between the spreading corolla lobes impart a slightly frilled look to the flower.

In Minnesota there are 4 species of gentian (included in the genera Gentianopsis and Gentiana) that have large, open, blue flowers. Two of these, the fringed gentians (Gentianopsis), are annuals that have 4 rounded, conspicuously fringed petals. Gentiana affinis var. affinis most closely resembles the other member of Gentiana with open flowers, the downy gentian (G. puberulenta). Gentiana affinis var. affinis differs in having slightly smaller flowers that are a paler blue than the deep, almost purple blue of G. puberulenta, and it has pale "freckles" on the petals that are not present in G. puberulenta. It is also a wet-prairie species, whereas G. puberulenta is a species of well-drained upland prairie. Gentiana affinis var. affinis is the rarest of the 4 species of gentian in Minnesota and is distinguished by being a perennial rather than an annual, and having the free portion of the petals alternating with folds or plaits in the sinuses.

  Habitat

In Minnesota, G. affinis var. affinis is primarily associated with wet saline prairie, which may occur within a matrix of wet prairie, mesic prairie, or brush prairie communities. Within these habitats, G. affinis var. affinis is restricted to narrow ecotones that occur along moisture gradients. Most of the occurrences of wet saline prairie are in zones of wet prairie located adjacent to glacial Lake Agassiz beach ridges, and the zones of salt accumulation are often associated with the shallow toeslopes of the beach ridges. Common associated grasses include Andropogon gerardii (big bluestem) and Muhlenbergia richardsonis (mat muhly grass). Sedges and rushes are also important in the habitat, and may include Carex tetanica (rigid sedge), C. hallii (Hall's sedge), and Juncus alpinoarticulatus (alpine rush).

  Biology / Life History

Gentiana affinis var. affinis is a perennial forb with conspicuous bee-pollinated flowers. It reproduces entirely by seeds, which have no specialized structures for dispersion. Dispersal vectors have not been identified, but short distance dispersal is probably accomplished by insects, wind, and gravity, and long distance dispersal by birds or small mammals. Given the fire-maintained habitat in which G. affinis var. affinis is found, it is reasonable to assume it is fire-adapted, although no fire experiments have been reported.

  Conservation / Management

The conservation challenge presented by G. affinis var. affinis is protection and management of its prairie habitat. If the habitat is of sufficient size to maintain a population of suitable pollinators, and it is shielded from conflicting land use activities, then management is rather straight forward. Potentially incompatible land uses include livestock grazing and annual harvesting of hay. There are no detailed studies that relate livestock grazing to a direct decline in G. affinis var. affinis, but it is known that G. affinis var. affinis is found only on prairies that have not been heavily grazed in the past. In addition to actually eating or trampling the plant, livestock can also cause soil compaction and an increase in non-native species. Hay harvesting can have direct negative effects on G. affinis var. affinis by removing the flowering portion of plants, thereby preventing reproduction. However, if haying is delayed until after the seeds have matured (September - early October), it may actually favor the species by scattering seed, scarifying the soil surface, and reducing the competitive vigor of other plants. In terms of management, it may also be necessary to reintroduce a regime of periodic dormant-season burns. Burns may help control excessive growth of shrubs and the build-up of thatch.

  Best Time to Search

The best time to search for G. affinis var. affinis is when flowers are present during the months of August and September.

  Conservation Efforts in Minnesota

A number of intact prairies that have sizeable populations of G. affinis var. affinis have been acquired by state and federal conservation agencies. In most cases, the prairies are being managed for the benefit of the native prairie vegetation and associated wildlife. However, the effects of current management on G. affinis var. affinis are not being monitored.

  References and Additional Information

Pringle, J. S. 2023. Gentiana. Pages 72-91 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 14. Oxford University Press, New York, New York.

The Great Plains Flora Association. 1986. Flora of the Great Plains. University Press of Kansas, Lawrence. 1,402 pp.