Solidago sempervirens
Solidago houghtonii
seaside goldenrod, verge d'or toujours verte
Houghton's goldenrod
1–10(–20+), erect or ascending, glabrous throughout or hairy in arrays.
1–5+, erect, slender, glabrous.
rosettes present at flowering;
basal and proximal cauline tapering to long, winged petioles sheathing stems or nearly so, blades narrowly ovate to oblanceolate, 100–400 × 10–60 mm, thick or fleshy, entire, acute, glabrous;
mid to distal cauline usually numerous, sessile, blades lanceolate, 40–60 × 5–10 mm, reduced distally, thick or fleshy, bases sometimes subclasping, margins entire.
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.
2–3 mm, glabrous or sparsely hairy.
5–6.2 mm, sparsely to moderately strigillose;
bracteoles 0–2, linear.
3–7 mm.
campanulate, (5.5–)6–8(–9) mm.
8–17;
laminae 5–6.2 × 0.4–0.6 mm.
6–12 (pale to bright yellow);
laminae 7.4–7.9 × 0.5–0.6 mm.
10–22;
corollas 3–3.2 mm, lobes 0.5–1.2 mm.
8–15;
corollas 4–4.3 mm, lobes 0.9–1.5 mm.
in 3–4 series, unequal, lanceolate, margins ciliate, apices acute.
in 3–4 series, unequal, linear to oblanceolate, margins ciliate, weakly striate, obtuse to rounded.
20–500, secund, in paniculiform arrays, secund-pyramidal to broadly club-shaped, sometimes leafy proximally, at least proximal branches spreading-recurved, branches and peduncles bracteolate, bracteoles reduced distally.
(2–)5–50(–100+), not secund, in corymbiform arrays, branches and peduncles glabrous or moderately strigillose.
(obconic) 1.1–1.5 mm, moderately strigose;
pappi 3.8–4 mm (slightly clavate).
obconic, 1.4–1.8 mm, glabrous, ribs sometimes dark;
pappi of bristles 4–5.5 mm, clavate.
= 54.
Solidago sempervirens
Solidago houghtonii
Subspecies 2 (2 in the flora).
Solidago sempervirens is common along the seacoast from the Gulf of St. Lawrence to central America and the northern West Indies. Introduced populations are sometimes very large near the Detroit River and Lake Erie in southwestern Ontario, eastern Michigan, and adjacent Ohio. A second disjunct group of populations occurs in Illinois and Indiana in the Chicago area at the southern end of Lake Michigan. Two mostly geographically separate subspecies can be recognized in the flora range. A race also occurs in the Azores and is undoubtedly introduced there [Solidago sempervirens var. azorica (Hochstetter ex Seubert) H. St. John]. Plants cultivated in European gardens have been labeled S. sempervirens var. viminea (Aiton) A. Gray.
(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. Involucres 4–7 mm, rays 12–17, disc florets ca. 17–22; Newfoundland to New Jersey, locally to Virginia | subsp. sempervirens |
1. Involucres 3–4 mm, rays 7–11, disc florets ca. 10–16; Massachusetts to Texas and southward | subsp. mexicana |
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