I live in zone 7a, and was recently rezoned to 7b, but in my garden we have 7a temps. We had frost several nights last week, and 2 nights below freezing. This yellow brug came through just fine. I didn't cover it. These pictures were taken this evening.
I did cover Klein Lady, she had some frost damage on the upper branches, the lower branches are fine, and she's still blooming.
The yellow brug has been coming back from the roots for years, and this is the 2nd year that Klein Lady has also come back from the roots. I can't stand looking at the dead stems so I do cut them back once the stems are fully dead, and I mulch them lightly with pine straw.