No answers for you, but I had the same problem. I finally just ripped it out after five years of dealing with the browning edges. I guess I didn't like it enough to figure out what was wrong.

That's what it did at my place, too.

This is normal for Echinops. There is no problem with the plant, nor is it the fault of the gardener. Mine do it all the time.

Because this trait is very unattractive, Echinops should be either planted in the back of the boarder, or have some smaller plant in front of it to hid the dying foliage. How about planting a smaller Helenium or a dwarf-ish grass?

If you decide to get rid of the Globethistle, how about planting Eryngium, Sea Holly? It looks somewhat similar but does not have the dying foliage troubles.
Hope this has helped you some.
CMK

I had it once & planted while it was still in the nearly pure peat based growing medium. That caused alot of die off of lower leaves & finally killed the plant from staying to wet for a prolonged period, after a heavy rainfall.
I think they need good drainage, with sandy soil & no peat to grow better.

So glad I read this thread and found out the horrible foliage wasn't because I didn't have it in the right place or did something to the 4 plants I have.

Last year the foliage was ugly even without any blooms. Slugs love it.

Since this was their first blooming year I was a bit disappointed as there wasn't much of a "blue" tint to them. Mostly greyish. I moved one earlier this year and didn't think I got the taproot but it survived and bloomed in new location.

Have annual blue salvia in front of it which covers a multitude of sins all over the garden.

hmm.. my echinops foliage is still looking fine. I have sandy soil and a raised bed, the plants are a year old, and it's been a rainy summer. And yet, I'm having doubts about these plants - the bloom season is fairly short, and in this particular lighting situation (by a south-facing wall) they're just a green blur for most of the time. They would stand out better if lit from behind, no doubt.
One good thing about Echinops is the way it stays upright, and is strong enough to support other plants. Eryngium has a longer-lasting blue color, but flops quite a lot for me.

Mine are drying off at a young stage few weeks after transplanting