Solidago elongata
Solidago houghtonii
Cascade Canada goldenrod, narrow goldenrod, west coast Canada goldenrod, west coast goldenrod, west coast or Cascade Canada goldenrod
Houghton's goldenrod
1–20+, erect, proximally sparsely to moderately strigoso-villous, distally usually moderately to densely so.
1–5+, erect, slender, glabrous.
basal 0;
proximal cauline sessile, blades narrowly to broadly oblanceolate, 35–75(–100) × (6–)7.5–14(–20) mm, proximal much smaller, tapering to bases, margins subentire or finely serrulate to coarsely, sharply serrate (teeth 0–9 per side), ciliate, 3-nerved, sometimes obscurely so, apices acute, abaxial faces glabrate to sparsely short-strigose, adaxial glabrous;
mid to distal cauline sessile, blades oblanceolate, becoming lanceolate distally, 20–60 × 4–8(–11) mm, largest near mid stem, somewhat to much reduced distally, margins entire or finely serrulate, rarely serrate (teeth 1–8 per side), usually becoming entire to sparsely serrulate distally, ciliate, apices acute, faces glabrous or sparsely strigoso-villous, more so along abaxial nerves.
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.
2–7 mm, sparsely to moderately short strigoso-villous;
bracteoles 1–3, linear, rarely minutely stipitate-glandular.
5–6.2 mm, sparsely to moderately strigillose;
bracteoles 0–2, linear.
narrowly campanulate, 2.5–3.5(–4) mm.
campanulate, (5.5–)6–8(–9) mm.
(8–)11–15(–17);
laminae 1–2.5 × 0.1–0.4(–0.7) mm.
6–12 (pale to bright yellow);
laminae 7.4–7.9 × 0.5–0.6 mm.
(3–)5–11(–16);
corollas 2.6–3.7(–4) mm, lobes 0.5–1.2 mm.
8–15;
corollas 4–4.3 mm, lobes 0.9–1.5 mm.
in 3–4 series, strongly unequal, margins sparsely long ciliate, acute, faces glabrous, rarely sparsely minutely stipitate-glandular;
outer lanceolate, inner linear-lanceolate.
in 3–4 series, unequal, linear to oblanceolate, margins ciliate, weakly striate, obtuse to rounded.
12–500+, sometimes secund, in short to long, thyrsiform or narrowly secund-pyramidal paniculiform arrays, usually congested, club-shaped to rarely wand-shaped, (2.5–) 10–20 × (2–)4–8(–10) cm, branches usually ascending or sometimes arching spreading.
(2–)5–50(–100+), not secund, in corymbiform arrays, branches and peduncles glabrous or moderately strigillose.
(narrowly obconic) 1–1.5 mm, sparsely to moderately strigose;
pappi 2.5–3.3 mm.
obconic, 1.4–1.8 mm, glabrous, ribs sometimes dark;
pappi of bristles 4–5.5 mm, clavate.
= 18, 36.
= 54.
Solidago elongata
Solidago houghtonii
In California, coastal plants of Solidago elongata often have thicker leaves; those of the Sierras are often membranous and obscurely triple-nerved. This species can be similar to S. lepida, which usually has much larger distal cauline leaves.
(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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