Solidago brachyphylla
Solidago houghtonii
Dixie goldenrod
Houghton's goldenrod
1–5, sparsely to moderately strigoso-puberulent.
1–5+, erect, slender, glabrous.
basal petioles 3–5 cm, blades oblanceolate or spatulate to ovate or rotund, 2–4 cm (excluding petioles);
cauline (numerous) subsessile or sessile, blades elliptic or lance-elliptic to ovate, mid mostly 25–50(–65) × 10–25 mm, distal much reduced;
branch leaf petioles 1 mm, blades ovate, 5–15 (excluding petioles) × 2–10 mm.
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.
linear, 1–3 mm, bracteate.
5–6.2 mm, sparsely to moderately strigillose;
bracteoles 0–2, linear.
narrowly campanulate, 3–5 mm.
campanulate, (5.5–)6–8(–9) mm.
0(–2).
6–12 (pale to bright yellow);
laminae 7.4–7.9 × 0.5–0.6 mm.
4–8;
corollas 3 mm, lobes 1 mm.
8–15;
corollas 4–4.3 mm, lobes 0.9–1.5 mm.
in 3–4 series, lanceolate, strongly unequal, margins ciliate, apices acute, glabrous.
in 3–4 series, unequal, linear to oblanceolate, margins ciliate, weakly striate, obtuse to rounded.
75–200 in open paniculiform arrays, branches divaricate, ascending to recurved, weakly to strongly secund, to 50 cm, secondary branches less than 3 cm.
(2–)5–50(–100+), not secund, in corymbiform arrays, branches and peduncles glabrous or moderately strigillose.
2.5–3 mm, moderately short-strigose;
pappi 2 mm.
obconic, 1.4–1.8 mm, glabrous, ribs sometimes dark;
pappi of bristles 4–5.5 mm, clavate.
= 18.
= 54.
Solidago brachyphylla
Solidago houghtonii
Solidago brachyphylla possibly occurs also in Mississippi.
(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.)
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