Solidago simplex
Solidago houghtonii
alpine goldenrod, dune goldenrod, Mt. Albert goldenrod, Rand's goldenrod, spikelike goldenrod, sticky goldenrod
Houghton's goldenrod
1–10+, ascending to erect, proximally glabrous, strigose in arrays.
1–5+, erect, slender, glabrous.
basal and proximal cauline petiolate, blades narrowly oblanceolate, (20–)50–100(–160) × (2–)5–16(–56) mm, margins serrate to crenate, apices acute to obtuse, glabrous;
mid and distal sessile, similar, blades lanceolate to linear, 12–45 × 2–19 mm, reduced distally, margins entire to sparsely serrate, sometimes resinous.
basal tapering to long, winged petioles, blades ovate, to 7–22 mm wide, margins entire, apices acute, faces glabrous;
proximal cauline tapering to winged petiole-like bases partially clasping stems, blades sometimes 3-nerved (2 prominent lateral nerves arising proximally and running alongside midnerve for some distance before diverging), linear oblanceolate, 158–177 × 7–22 mm, margins entire, ciliate, apices acute to obtuse, glabrous;
mid to distal sessile, blades linear lanceolate, mid often 3-nerved (obscurely sometimes), distal 1-nerved, 47–100 × 4–10 mm, reduced distally.
3.1–10.3 mm, glabrate to sparsely strigillose;
bracteoles few, linear.
5–6.2 mm, sparsely to moderately strigillose;
bracteoles 0–2, linear.
campanulate, 3–7 mm.
campanulate, (5.5–)6–8(–9) mm.
7–16;
laminae 2–5 × 0.7–0.9 mm.
6–12 (pale to bright yellow);
laminae 7.4–7.9 × 0.5–0.6 mm.
6–31;
corollas 4–4.9 mm, lobes 0.6–1.3(–2) mm.
8–15;
corollas 4–4.3 mm, lobes 0.9–1.5 mm.
(in 3–4 series) strongly unequal, often resinous;
outer ovate, acute, inner linear-oblong, obtuse.
in 3–4 series, unequal, linear to oblanceolate, margins ciliate, weakly striate, obtuse to rounded.
3–150, not secund, in narrowly elongate, paniculiform arrays, broadly so in robust plants (12.5–19 × 2.5–3 cm wide), consisting of short axillary and terminal racemiform clusters, proximal branches elongate in larger plants, branches glabrate to strigillose.
(2–)5–50(–100+), not secund, in corymbiform arrays, branches and peduncles glabrous or moderately strigillose.
narrowly obconic, 1.9–3.2 mm, sometimes with dark ridges, strigillose;
pappi 1.9–5.2 mm (bristles sometimes clavate).
obconic, 1.4–1.8 mm, glabrous, ribs sometimes dark;
pappi of bristles 4–5.5 mm, clavate.
= 54.
Solidago simplex
Solidago houghtonii
Varieties 7 (7 in the flora).
The somewhat viscid-resinous heads of Solidago simplex are its most distinctive feature, separating it from similar sympatric species. G. S. Ringius (1985) did a detailed multivariate analysis of the S. spathulata/S. simplex complex (the latter under the name S. glutinosa). The cytogeography of the species complex was presented by Ringius and J. C. Semple (1987). Neither study included data on the next three species occurring in the southeastern United States.
The species is divided into two subspecies and seven varieties following G. S Ringius (1985) and J. C. Semple et al. (1999). Three varieties occur in the diploid transcontinental subsp. simplex: var. simplex, var. nana, and var. chlorolepis. Four varieties occur in the eastern North American tetraploid-hexaploid subsp. randii: var. monticola, var. gillmanii, var. ontarioensis, and var. racemosa. Except for var. simplex, varieties are restricted to different habitats in relatively limited ranges.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The large involucres and the presence of the unique 3-nerved proximal and mid cauline leaves distinguish Solidago houghtonii from other taxa in sect. Ptarmicoidei. The 3-nerved venation pattern may be morphologic evidence of a hybrid origin for S. houghtoni between a parallel-nerved member of sect. Ptarmicoidei and a 3-nerved member of subsect. Triplinerviae. Molecular data indicate that S. gigantea may have been one of the parental species (P. Laureto, pers. comm.).
Reports of Solidago houghtonii from New York have been rejected as being based on misidentified specimens (J. K. Morton 1979). Some collections have the large involucres typical of S. houghtonii; molecular data indicate that the species is present in Genessee County, New York (P. Laureto, pers. comm.).
Solidago houghtonii can be difficult to distinguish from S. ohioensis × S. ptarmicoides hybrids because both have hairy peduncles in arrays. The hybrids have pale yellow rays even when fresh; post-flowering rays of S. houghtonii can be pale yellow. J. K. Morton (1979) hypothesized an allopolyploid origin for the hexaploid S. houghtonii via an unreduced gamete of S. ohioensis × S. ptarmicoides backcrossed to S. ohioensis with subsequent chromosome doubling. Additional work is needed to confirm this hypothesis. An aberrant collection (M. R. Penskar 1067, MICH) had about 400 heads (mostly in bud) due to axillary branches developing along nearly the entire stem; stems usually have fewer than 50 heads. Some plants from Michigan are more robust than those found in Ontario.
Solidago houghtonii is listed by the U.S. Fish and Wildlife Service as threatened in Michigan. It is in the Center for Plant Conservation’s National Collection of Endangered Plants.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Basal and cauline leaves spatulate to orbiculate, apices obtuse to rounded; cypselae moderately to densely strigose (S. simplex subsp. simplex) | → 2 |
1. Basal and cauline leaves spatulate to obovate, apices usually acute; cypselae sparsely to moderately strigose (S. simplex subsp. randii) | → 5 |
2. Cauline leaves 5–16 (longest 60+ mm); w North America, disjunct along shores of upper Great Lakes and in s Quebec | var. simplex |
2. Cauline leaves 2–7 (longest to 60 mm); alpine slopes, w North America, Mt. Albert, Gaspé, Quebec | → 3 |
3. Shortest phyllaries 1.4–2 mm; disc corollas 3.9–4.2 mm; serpentine soils, Mt. Albert, Gaspé, Quebec | var. chlorolepis |
3. Shortest phyllaries 2.1–3.1 mm; disc corollas 4.2–5.4 mm; alpine slopes, Rocky Mountains, Cascade Mountains, Vancouver Island. | → 4 |
4. Basal leaves usually spatulate, rarely broadly elliptic, proximal blades gradually attenuated to winged petioles, margins weakly crenate; alpine slopes, Rocky Mountains | var. simplex |
4. Basal leaves orbiculate to broadly elliptic, proximal blades abruptly attenuated to winged petioles, margins distinctly crenate; alpine slopes of Cascade Mountains, Vancouver Island | var. nana |
5. Proximal cauline leaves spatulate to obovate, (5–)10–42 mm wide; leaf margins often sharply serrate | → 6 |
5. Proximal cauline leaves lanceolate to narrowly spatulate, 2–10(–21.5) mm wide; leaf margins entire or dentate, rarely serrate | → 7 |
6. Plants (10–)18–53(–83) cm, arrays tending to be compact, virgate; proximal cauline leaves (5–)10–22(–31) mm wide, margins crenate to serrate; barren, rocky, non-alpine uplands; se Quebec, New England, New York | var. monticola |
6. Plants (20–)38–73(–84) cm, robust, arrays tending to be paniculiform; proximal cauline leaves (6–)7.5–24(–42) mm wide, margins often sharply serrate; sand dunes, Lake Michigan, n Lake Huron | var. gillmanii |
7. Cauline leaves (3–)12–33(–58); peduncle bracteoles 2+; calcareous rocky riverbanks, e Quebec s to West Virginia and Maryland | var. racemosa |
7. Cauline leaves (2–)4–13(–24); peduncle bracteoles 1–3(–4); rocky shores, Lake Superior, n Lake Huron | var. ontarioensis |
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