Iron in the soil will turn them blue again, it is just not a quick fix.When I planted mine (before the drought some years ago killed them) I took a bunch of chopped up nails, nuts and bolts (all steel) and mixed that in with the soil in the holes I planted them in. I needed one more, and planted it also a few days later, but being basically lazy, didn't put any metal in with it. All were a nice blue except that one, it was a pink with a few light blue flowers.All the metal I put in was bear metal stuff, no coatings on it. Smaller pieces leach iron faster.
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