Field Eryngo (Eryngium campestre) is an extremely rare plant, restricted to a handful of sites in the UK, but fairly common on the continent.
There is a plant at what is now Darenth Country Park which I knew and photographed in flower back in the early '80s. In those days it was under a Hawthorn (I think) bush, in moderate-length grass at the foot of a modest chalk slope.
Today I went out with Mervyn Brown, a champion of the plant here (who is another old wildlife friend I hadn't seen for many years, but who recently made a welcome but thoroughly unexpected appearance at my front door on the strength of seeing something I'd posted on the net ....) to help measure the number of growths and leaf area, and cut back some of the surrounding scrub.
Thirty years on, and the Eryngo clings to its precarious existence, but the whole site has been seriously degraded by excessive rabbit grazing, and only small leaves of the plant (growing up from the rootstock) were present, in an area of pretty bare soil. Mervyn later showed me some seed-raised specimens off this plant in his garden.
More on Eryngium campestre, including photographs , and notes from Mervyn on the state of the Darenth site and cultivation of the plant can be found here: