Houghton's goldenrod (Solidago houghtonii) COSEWIC assessment and status report: chapter 3
Species Information
Name and classification
Scientific name:
Solidago houghtonii T. & G.
Synonym:
Oligoneuron houghtonii (T. & G. ex Gray) Nesom
Common names:
Houghton’s goldenrod, Verge d’or de Houghton
Family
Asteraceae or alternatively Compositae (Aster family)
Major plant group:
Dicot flowering plant
Houghton’s goldenrod is widely recognized as a distinct species (e.g., Gleason, 1952; Semple and Ringius, 1983); however, there is some debate about its origin. Morton (1979) hypothesizes that Solidago houghtonii evolved from a hybrid of S. ptarmicoides and S. ohioensis that backcrossed with S. ohioensis and gained fertility through subsequent chromosome doubling (amphidiploidy), while Semple and Ringius (1992) suggest that S. riddellii might have been involved in the origin of Houghton’s goldenrod rather than S. ohioensis.
Description
Houghton’s goldenrod is a slender perennial whose shoots grow from an underground stem (caudex) arising from a fibrous root system; plants have slender reddish hairless stems that grow to 30-60 cm high and finely hairy flower stalks (Semple & Ringius, 1992; Gleason, 1952). Basal rosettes are comprised of ovate hairless leaves up to 2 cm wide. Lower stem leaves are linear, slightly clasping, up to 18 cm long and 2 cm wide, sometimes folded along the midrib. Leaves become smaller and less clasping further up the stem. The inflorescence is flat-topped, usually consisting of 5 to 30 flowering heads, sometimes up to 200 (Voss, 1996). The flower head consists of an involucre of bracts about 6-8 mm high surrounding about 20-30 flowers, including 6-12 bright yellow ray flowers (Semple & Ringius, 1992; Gleason, 1952; see Figure 1).
Houghton’s goldenrod is most likely to be mistaken for grass-leaved goldenrod (Euthamia graminifolia) or Ohio goldenrod (Solidago ohioensis). Grass-leaved goldenrod can be distinguished by the absence of basal leaves during flowering time, smaller ray flowers, and considerably more leaves on the stem. Ohio goldenrod is more robust, has smooth flower stalks and broader leaves. The actual hybrid between S. ohioensis and S. ptarmicoides, from which S. houghtonii is thought to have evolved, can be distinguished when fresh by its pale lemon coloured flowers (Morton & Venn, 1984).
Good line drawings are available in Gleason (1952) and in Semple and Ringius (1992).
Figure 1. Houghton’s goldenrod (from Semple and Ringius 1983, with permission).
- plant habit;
- lower stem leaf;
- flowering head with only one ray flower illustrated;
- involucre bract;
- mature fruit with corolla still attached in the centre
