Saxifraga paniculata
Saxifraga hyperborea
saxifrage paniculée, White Mountain saxifrage
brook saxifrage, pygmy saxifrage, saxifrage hyperboréale
basal and cauline;
petiole absent;
blade oblong to obovate, unlobed, [5–]8–35[–50] mm, leathery-fleshy, margins finely serrate (teeth whitish), proximally ciliate, with lime-secreting hydathode (secretions obvious), apex obtuse to ± acute, surfaces glabrous.
basal and cauline, (cauline 1–3, dissimilar from basal, reduced);
petiole ± flattened, (2–)5–35 mm;
blade reniform to orbiculate, (2–)3–5(–7)-lobed (lobes rounded), (2–)3–6(–10) mm, thin or slightly fleshy, margins entire, eciliate or sparsely stipitate-glandular, (inconspicuous nonsecreting hydathodes sometimes present), apex acute, surfaces glabrous or sparsely hairy.
2–20-flowered, narrow, distally branched thyrses or cymes, sometimes solitary flowers, 6–40 cm, purple-tipped stipitate-glandular;
bracts sessile.
2–5-flowered cymes, sometimes solitary flowers, 1–5 cm, tangled, purple-tipped stipitate-glandular;
bracts petiolate.
sepals erect, (often reddish), oblong to ovate, margins eciliate, surfaces hairy;
petals white to cream or pink, sometimes orange- or purple-spotted, elliptic to oblong or obovate, 3–6 mm, longer than sepals;
ovary 1/2+ inferior.
(hypanthium U-shaped in longisection, sparsely to densely long stipitate-glandular);
sepals erect, (sometimes purple), ovate to lance-oblong, (1.5–2.1 mm wide), margins eciliate, surfaces ± stipitate-glandular;
petals purple or white, often midvein ± purplish, faded when dried, not spotted, oblong, (1.5–)2–3.4(–5) mm, equaling or to 1.5 times sepals;
ovary 1/2 inferior.
= 28.
= 26.
Saxifraga paniculata
Saxifraga hyperborea
C. Reisch (2008) studied the phylogeography of Saxifraga paniculata. North American populations originated postglacially from refugia south of the ice. Reisch suggested that North American populations may belong to subsp. laestadii (Neuman) T. Karlsson, found also in Iceland and northern Norway. The Manitoba report originates from Clearwater Lake (R. Humphrey s.n., 13 Sept. 1993, WIN 62868), where shaded, cool, calcareous cliffs provide suitable habitats that also host other eastern disjuncts (B. A. Ford, pers. comm.).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Reports of Saxifraga hyperborea from Mount Washington, New Hampshire (e.g., Á. Löve and D. Löve 1964) require confirmation; all specimens examined from this location appear to be S. rivularis. C. L. Hitchcock (1961) treated all western material as S. debilis, including that of the Pacific Northwest that is included here. For Colorado, W. A. Weber (1990) appears to have applied the name S. rivularis to what we call S. hyperborea, and S. hyperborea subsp. debilis to what we call S. debilis. P. K. Holmgren and N. H. Holmgren (1997) included under their broad concept of S. rivularis both S. hyperborea and S. debilis, noting that the plants had gone usually under the latter name. Both species are present in the Rockies and the Intermountain Region.
In northeastern North America, Saxifraga hyperborea and S. rivularis are often sympatric, although the latter is absent from the extreme north. The major distinguishing feature between diploid S. hyperborea and tetraploid S. rivularis is the presence of rhizomes in the former and their absence in the latter (see key), a character that is sometimes difficult to interpret on herbarium sheets. Plants of S. hyperborea are usually smaller (2–5 cm) and reddish (sometimes green), with usually three- to five-lobed leaves and petals about one and one-half times longer than sepals, while plants of S. rivularis are taller (5–10 cm) and usually green (although sometimes reddish, particularly in the western var. arctolitoralis), with usually five-lobed leaves and petals two to three times longer than sepals.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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