List of Wisconsin's goldenrod species with links to photos.

Acknowledgements

INTRODUCTION TO GOLDENRODS

As currently understood, twenty four species of goldenrods have been reported to occur in Wisconsin. Some authors would raise the number of species to 25 by distinguishing Solidago altissima as a species separate from S. canadensis. Others have placed S. ptarmicoides in the genus Aster, reducing the number to 23. Perhaps 6-10 species could be considered common, at least in some significant portion of the state, and other species may be locally common in a particular area. One species, Solidago canadensis, is so common, widespread and variable as to be emblematic of the genus.

Although the common perception of goldenrods is that of the robust, bright yellow fields of Solidago canadensis, two of the species have white flowers (Solidago bicolor and S. ptarmicoides), several prefer wet habitats (e.g. S. patula, S. riddellii, S. uliginosa, Euthamia graminifolia--sometimes) and several do well in forests (e.g. S. flexicaulis, S. patula, S. ulmifolia). Four species of Wisconsin's goldenrods are rare enough to be assigned protective status (Solidago caesia is endangered, S. simplex is threatened, S. ohioensis and S. sciaphila are special concern ). Two species (S. mollis and S. rugosa) are rare escapes from cultivation, each known from only one site in the state, though both are native elsewhere in the U.S.A.

IDENTIFICATION OF GOLDENROD SPECIES

The goldenrods can be difficult to identify and there is a strong tendency for beginners to "identify" more species than are present. This is especially true of S. canadensis with diverse forms arising from internal and external factors that can be confusing even within a single clone. Unlike many other taxa, the characteristics of the flowers are often not the most important issue for identification. Shape of the inflorescence and characters of the leaves are often critical and each has its challenges. Individual inflorescences may not conform closely to the standard descriptions for a given species and stems that have been damaged during development may fail to meet expectations.

Many of the species of goldenrod are large enough to tempt inexperienced collectors to take only the upper portion of the stem. It is not necessary to collect the below-ground structures, but it is wise to collect one or more full stems, because the lower stem leaves may be of different shape and/or size than the upper leaves and they may be critical in negotiating the key. The lower leaves of some species may shrivel and fall off late in the growing season, making identification difficult if the broader suite of characters is not recognized. As in the collection of all plant vouchers, it is a good idea to spend a few minutes to determine that the specimens collected are representative of the population.

List of Wisconsin's goldenrod species with links to photos.

Other helpful sources of information:

Salamun, P. J. 1964 [“1963”]. Preliminary Report on the Flora of Wisconsin. 50. Compositae III (the genus Solidago). Transactions of the Wisconsin Academy of Sciences, Arts and Letters. 52:353– 3 8 2 . This treatment is a bit old, but there is a well written key and much good information specific to the goldenrods of Wisconsin. The three Euthamia species were included in Solidago at this time also.

Voss, Edward G.1972. Michigan Flora. Cranbrook Institute of Science.
Part III. Dicots (Pyrolaceae - Compositae). Bulletin 61. Includes a good key to the goldenrods and text on the habitat of each species by a knowledgeable field botanist. The key is a good match for Wisconsin except it does not include the rare SW Wisconsin species Solidago sciaphila and the rare weed Solidago mollis, and he recognizes only two species of Euthamia (excludes S. gymnospermioides). The key also includes the rare S. houghtonii and the introduced S. sempervirens, neither of which has been reported from Wisconsin.

Atlas of the Wisconsin Prairie and Savanna Flora by T.S. Cochrane & H.H. Iltis: Department of Natural Resources Tech. Bull. 191. Not all goldenrods are included, but there are excellent discussions of several species, including habitat, distribution information, flowering and fruiting time.