Heuchera macrorhiza Small. Section: Holochloa. Subsection: Villosae. Common name: Giant Alumroot. Phenology: (Late Apr) May-Jul (and sometimes reblooming Sep-Oct). Habitat: Cliffs, riverbanks, especially in calcareous or subcalcareous substrates. Distribution: S. WV, s. OH, and s. IN south through c. KY and c. TN to n. AL and ne. MS.
Origin/Endemic status: Endemic
Taxonomy Comments: This taxon has usually been disregarded in recent years, but is recognized by Chester et al. (1997). This plant is generally sharply distinct from typical H. villosa, and actually may be more closely related to H. arkansana. A few intermediates and intergrades with H. villosa may be encountered; they have been called H. villosa var. intermedia. In the Ozarks of AR, H. macrorhiza is replaced by the related H. arkansana Rydberg [H. villosa var. arkansana (Rydberg) E.B. Smith] with shorter and narrower inflorescence, shorter pedicels, and larger flowers. "Heuchera macrorhiza differs from typical villosa (Small 1898, F, W) in its relatively short, broad bractlets, which are densely long-ciliate (versus narrowly lanceolate to subulate, glabrous to thinly ciliate); bracts are oblong to spathulate, and at least the lower ones toothed (versus linear, mostly entire); its stems are "shaggily" villous (versus loosely); leaves are hirsute below, with long soft hairs along veins (versus glabrous to thinly hairy, with appressed stiff hairs along veins); leaf lobes are all shallow, much broader than long (versus deep and sharp, especially the terminal); rhizomes are ca. 1-2 cm thick (versus 5-9 mm)" (Campbell 2012).
Other Comments: Heuchera macrorhiza is popular horticulturally as a native wildflower, almost invariably labeled as "Heuchera villosa".
Synonymy ⓘ: = S, S13; = Heuchera villosa Michx. var. macrorhiza (Small) Rosend., Butters, & Lakela — G, Tn; > Heuchera villosa Michx. var. intermedia Rosend., Butters, & Lakela — F, WV, Rosendahl, Butters, & Lakela (1936); > Heuchera villosa Michx. var. macrorhiza (Small) Rosend., Butters, & Lakela — F, WV, Rosendahl, Butters, & Lakela (1936); < Heuchera villosa Michx. var. villosa — C, FNA8, K4, Wells (1984). Basionym: Heuchera macrorhiza Small 1898
Links to other floras: < Heuchera villosa var. villosa - FNA8
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Heliophily ⓘ: 5
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Horticultural Information
No horticultural data found for this taxon.