Petioles glabrous or very short to sparsely long stipitate-glandular. Flowers: hypanthium free 0.6-1.5 mm, urceolate; petals greenish, white, or pink, narrower than sepals, margins entire or finely dentate. 2n = 14. Flowering Apr-Jun. Rich woods often over base-saturated granite and gneiss, or in shallow, rocky soil; 70-1300 m; Ont.; Ala., Ark., Conn., Del., Ga., Ill., Ind., Ky., La., Md., Mich., Miss., Mo., N.J., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Va., W.Va. Variety americana is widely distributed from Connecticut to Georgia and from southern Ontario and Ohio to Oklahoma and northwestern Louisiana. It intergrades with Heuchera pubescens and H. richardsonii where their ranges overlap, but not with H. longiflora, H. parviflora, or H. villosa, which also share overlapping ranges with it.
From Flora of Indiana (1940) by Charles C. Deam
[Deam recognized three varieties of H. americana.] [Variety brevipetala, a form with more or less glabrous petioles,] is is our most common alumroot and is frequent throughout the state although there are no records from the northwestern part. It is generally found on or near the tops of wooded slopes along streams or on the slopes of ravines. According to the monographers of the genus, the typical form of this species is restricted to the Appalachian Mountains from southern Pennsylvania southward to North Carolina and Tennessee and this variety [var. brevipetala] and the two following [var. hirsuticaulis and var. interior] are the western allies of it. [Deam's var. hirsuticaulis has densely hirsute petioles and flowers mostly 4-4.5 mm long.] The habitat of this variety is similar to that of the preceding [var. interior]. This variety, in its morphology, is about midway between the species and Heuchera Richardsonii R. Br., which is restricted to the eastern Rocky Mountains and plains, and seems to have a range about midway between the two species with its eastern extension in west central Indiana. [Deam's var. interior has densely hirsute petioles and smaller flowers, mostly 3-3.5 mm long.] The habitat of this variety is the same as that of [var. brevipetala], but the plant is probably less frequent.