Sounds like either a powdery mildew, too much sun or not enough water or combination of them. I have had the flower stems turn brown and dry up, but the leaves have always been fine. One I've had for 7 yrs and the other for 4 yrs.

Kat

I have never heard of Jack Frost doing this. I have one that is about 7 years old and I have no idea if the foliage goes bad or not. Mine does its thing, looks beautiful for about a month, then disappears completely under the Variegated Solomon Seals, Cinnamon ferns, and other plantings in my overplanted, overcrowded side garden, so I never see or think of it or see it again until spring, when it pops up and looks beautiful once again. :)

I've not had good luck with the "speciality" brunneras (i.e. variegated), they always seemed to get very cripsy and look cr*ppy and just weren't as vigorous as the plain 'ol green variety. I eventually shovel-pruned mine and am not even tempted by them anymore.

Brunnera likes moist conditions, it's the over-riding factor in growing them well. Even the old ironsides green ones get crispy if the soil is too dry. They never go dormant on me, but will look raggedy if there's not enough moisture. They don't really like too much sun either - partial sun is good, full, hot sun isn't, especially if the soil doesn't retain a lot of moisture.

Mine always looks pretty good. It's only this ones first year. I bought this one at Forestfarm.com I do have 3 others that are all doing pretty well. I have it in part shade and keep it watered so it doesn't go comepletely dry, and stays evenly moist. I do fertilize on occasion with either Gardenville Sea Tea or whatever granular one I have. I don't do that but once a month or so. Now, I won't be doing it at all, as I want it to get ready for winter. Here's a pic of my Jack Frost earlier during the summer.

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I have the solid green ones, 'Jack Frost' and a white variegated one and none have done the turn black thing. The white variegated one does revert to green every chance it gets though.

Mine is also turning black It got overrun by some perennial geraniums that I had to cut back. Them it started to decline. I’m sure its a cultural problem and too little water as it aj