Gentiana

Individuals with white flowers may be expected in all the species in which the corolla is ordinarily blue or purplish. Interspecific hybrids occur rarely.

1. Plaits [folds] between the corolla lobes distinctly longer than the lobes, toothed or erose; calyx lobes minutely ciliate.

G. andrewsii

1. Plaits distinctly shorter than the corolla lobes, entire or toothed; calyx lobes smooth, papillose, or ciliate.

2. Stem puberulent, especially on the angles; calyx lobes linear, broader at the very base; corolla open at anthesis.

G. puberulenta

2. Stem glabrous; calyx lobes broadest above the base (or linear in G. linearis and G. rubricaulis); corolla nearly closed at anthesis.

3. Calyx lobes distinctly keeled basally on the underside and in one species also minutely ciliate; apex of plaits between the corolla lobes ± strongly erose or at least bifid; plants only in the southern half of the Lower Peninsula.

4. Leaf blades (at least the upper) (1.7–) 2.7–5 cm broad; calyx lobes and leaves not ciliate; flowers white, marked with greenish.

G. alba

4. Leaf blades less than 2 cm broad; calyx lobes (and at least the involucral leaves) densely ciliate; flowers mostly blue.

G. saponaria

3. Calyx lobes without a keel or cilia (at most minutely papillose or scabrous); apex of plaits between the corolla lobes broadly triangular, terminating in a single off-center tooth (sometimes with a much smaller subsidiary tooth on each side); plants only in the Upper Peninsula and north half of the Lower Peninsula (though farther south in Ontario).

5. Leaves deep green, linear or nearly so, not over 1 cm broad; calyx lobes green throughout, ± exposed by the spreading, narrow involucral leaves.

G. linearis

5. Leaves ± pale green, lanceolate to ovate, at least the larger ones over 1 cm broad; calyx lobes green at most toward apex, usually well concealed by the broad, enveloping involucral leaves.

G. rubricaulis

All species found in Gentiana

Gentiana albaWHITE GENTIAN, YELLOWISH GENTIAN 
Gentiana andrewsiiCLOSED GENTIAN, BOTTLE GENTIAN 
Gentiana linearisBOG GENTIAN, NARROW-LEAVED GENTIAN 
Gentiana puberulentaPRAIRIE GENTIAN 
Gentiana rubricaulisRED-STEMMED GENTIAN, GREAT LAKES GENTIAN 
Gentiana saponariaSOAPWORT GENTIAN 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 11, 2017. http://www.michiganflora.net/genus.aspx?id=Gentiana.