Semple, John C., Gordon S. Ringius and Jie Jay Zhang. 1999. The goldenrods of Ontario: Solidago L. and Euthamia Nutt. 3rd Edition. University of Waterloo Biology Series 39: 1-90.
The 30 species goldenrods in Ontario are members of two distinct genera, Solidago and Euthamia. Although sometimes included in the same genus, the two genera are not sister groups within the tribe. The Ontario species of the Solidago are placed into 2 sections and 7 subsections of the genus. Seven species and varieties of goldenrods are rare and either endangered or threatened in Ontario: Euthamia gymnospermoides, Solidago houghtonii, S. puberula, S. riddellii, S. simplex var. gillmanii, S. speciosa, and S. ulmifolia. One species is adventive and locally naturalized in southwestern Ontario: S. sempervirens. Several species are uncommon and limited to a single floristic zone, but are not so rare as to warrant special status; S. arguta and S. rigida. The majority of taxa are common throughout the province or in one of the major floristic zones.
Complete descriptions and illustrations of all taxa are included along with a key to all taxa. Distributional data are summarized in tabular form. Coloured illustrations of 28 species of goldenrods and several related taxa in the tribe are included in this edition of the Goldenrods of Ontario.
The following new names are proposed: Solidago subg. Oreochrysum (p. 23), Solidago asteroides (p. 72), Solidago hispida var. huronensis (p. 36).