| Apiaceae | Eryngium yuccifolium var. synchaetum | Southern Rattlesnake-master | Wet savannas, especially those over calcareous clay soils. | A Southeastern Coastal Plain endemic: se. NC to s. FL and west across the Gulf Coastal Plain, the exact range limits obscure. | 
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| Apiaceae | Eryngium yuccifolium var. yuccifolium | Northern Rattlesnake-master | Diabase barrens and glades, olivine barrens, pine savannas, pine flatwoods over loamy or clay soils, wet to dry prairies, other open sites with at least periodic moisture, generally in sites showing some prairie affinities. | Widespread in southeastern and midwestern North America, the exact range limits of the typic variety and var. synchaetum somewhat obscure; probably distributed from NJ, OH, s. MI, WI, MN, and NE south to Panhandle FL, AL, MS, n. LA, and e. TX. | 
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