Eryngiums, native and otherwise

I came across an interesting plant recently at the U.S. Botanical Garden in D.C. last weekend. In the Regional Garden section of the National Garden there were several patches of Eryngium aquaticum in full bloom. Though I was familiar with a couple of Eryngiums, this species was new to me. For a couple weeks I had been looking around for some sea holly after seeing the beautiful specimens at the Norfolk Botanical Garden. This native variety is very similar, although not quite as intensely blue as the European species (below - didn't get the exact species).

Though I've never seen it before, apparently it is native all along the Virginia coast. Has anyone had any experience with it? I didn't find a seed source on line, but I am planning to get some via mail-order this fall. At the D.C. Botanical garden the E. aquaticum was growing in large swathes in a low wet area of the garden, so maybe it would be better for a rain garden than a typical planting bed. It also appeared to be vigorously spreading.

I'm sure many of you are familiar with one of our other eryngiums, rattlesnake master (E. yuccifolium) this plant is commonly used in native plant gardens. The picture below is from the garden at the Williamsburg Public Library.

Interestingly (to me anyway), on a recent VNPS outing to Little Creek Resevoir, Donna Ware and Carolyn Will identified yet another species, E. prostratum (Creeping Eryngo). This little guy seems to also like wet conditions, as it was growing along the shores of the lake.

I wonder if I could hybridize it with the E. yuccifolium...sort of like a chihuahua and a Great Dane.