57a. Solidago altissima Linnaeus subsp. altissima
Solidago canadensis Linnaeus var. scabra (Muhlenberg ex Willdenow) Torrey & A. Gray; S. scabra Muhlenberg ex Willdenow
Involucres usually 3–4 mm. 2n = 36, 54.
Flowering Aug–Oct. Dry to moist soils, fields, roadsides, disturbed areas; 0–1000+ m; Man., N.B., N.S., Ont., P.E.I., Que., Sask.; Ala., Ariz., Ark., Calif., Conn., Del., Fla., Ga., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Utah, Vt., Va., W.Va.; Mexico.
Subspecies altissima is an escaped cultivar or has been introduced in Arizona, California, and Utah, and very likely in other western states. It is the most common and "weedy" member of subsect. Triplinerviae and has been introduced in many parts of the world. It replaces subsp. gilvocanescens in the eastern United States and adjacent Canada. Tetraploids are infrequent along the western edge of the subspecies’s distribution and rarely on glades in the southeastern United States. Hexaploids occur throughout the range. Array shape varies, narrower and elongate ones occurring in the southeastern United States; in Texas, such plants might be confused with Solidago juliae, which has more linear leaves. Further work is needed to analyze regional variants within each subspecies.