If you love the steelly-blue flower color of Eurasian eryngiums but lament that the native Eryngium yuccifolium lacks it -- then you might want to take a look at this obscure but outstanding wetland native. Eryngo does indeed produce large thimbles of --yes -- silver-blue flowers in summer on plants similar in size to rattlesnake-master. The linear basal leaves are similar in shape to those of its cousin, but less prominently toothed. Don't be fooled by the "wetland" part -- it does well in most any soil that's not too dry. Unaccountably rare.
Sun; moist humus-rich soil; 4'x2'; mid to late summer. Zone 5
Propagated from seed; deep 3.5-inch pots.
Photo: Mark T. Strong and Carol L. Kelloff