Our three species are all natives of Europe, whence they came to North America and became weeds. Hybrids may be expected wherever two or three species grow together. The spherical fruiting heads of goat’s-beard resemble those of dandelion, but are much larger and on leafy stems (besides having plumose rather than simple pappus-hairs).
Hybrids are rather easily recognized, especially those involving the purple T. porrifolius, for the heads are often a handsome red-orange or sometimes pale purplish with the bases of the ligules yellow. If the phyllaries are reddish-margined, only equaling the ligules, and/or the leaf tips curled, T. pratensis is the yellow parent. If the phyllaries are entirely green and the leaf tips straight, T. dubius is the yellow parent. Hybrids between the two yellow species are less easily spotted, but close examination again reveals a mixture of characters, such as phyllaries exceeding the ligules or peduncle inflated (as in T. dubius), but phyllaries reddish-margined and/or leaf tips curled (as in T. pratensis).
The most frequent hybrid, T. porrifolius × T. pratensis, is T. ×mirabilis Rouy. The hybrid between the two yellow species may be called T. ×crantzii Dichtl. First-generation hybrids are sterile, but derivatives rendered fertile by doubling of chromosomes (amphidiploids) have been described as species. Such fertile plants are not yet known from Michigan, but can be expected. See Soltis et al. (2008) for more information.
1. Ligules purple; pappus brownish.
1. Ligules yellow; pappus dingy whitish.
2. Margins of phyllaries green (or pale); leaf tips straight; ligules pale yellow, distinctly shorter than the longest phyllaries; pedicels much expanded beneath the heads.
2. Margins of phyllaries reddish purple (rarely green); leaf tips ± curled or curved; ligules bright yellow, as long as or longer than the phyllaries; pedicels scarcely if at all expanded.
All species found in Tragopogon
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. October 18, 2017. http://michiganflora.net/genus.aspx?id=Tragopogon.