I found a historical blog detailing Elizabeth Rainbow’s Skirrit Pie, and it mentions it can alternately be made using Eryngo roots from Eryngium maritimum and Eryngium campestre. Apparently one likes it salty and the other grows inland in a manner similar to Crambe.
Yes! I have tried it and it was tasty, although small. The root is a bit like dandelion. The problem is that it is a real pain to harvest (spiny) and very weedy here. Still, it has all the raw material of an interesting breeding project.
Walmart recently put out its bags of bulbs and roots for Spring, and lo and behold they have an ornamental Blue Sea Holly (Eryngium) which contains 4 roots for $5. Info I previously found online says this particular variety was developed from the inland form of the plant so I bought it thinking it might chance to produce some kind of edible root.