Hmmm ~ good questions, so here are MY observations to add to yours: I "neglected" to cut mine back in the fall and so not only is it coming back from the root, but it is also sprouting new growth along the old stems. To top it ALL off, the weeping shape of the shrub has allowed the sprouting new growth to root AGAIN into the surrounding soil, so I am beginning to wonder how many new starts I will have.
Even though we are two zones apart, our winter was also mild to the point of non-existence, so I wish I had cut the shrub back in the fall as usual. Working too many hours had a lot of plants getting away from me. Whew. It remains to be seen what the outcome of this will be but I wanted to add my observations to yours:)

yep.. you need to be googling the second latin name..

i have one that dies to the ground..

and one that does not ...

ken

I'm assuming you mean 'divaricata" which would be the 'Blue Butterflies'? I'm not sure what 'Sunshine Blue' is. It certainly doesn't look anything like the former.

Kevin

Z8b - C. divaricata (Snow Fairy is the one I'm growing) is an herbaceous perennial, dies to the ground each late Fall

But, most plants in the genus (clandonensis, incana etc) are woody shrubs or subshrubs and leave an existing framework over winter.

I never trim them down until the spring - this year I have them sprouting from the ground and along the stem - but just low along the stem. I'll cut last year's stems down pretty low. I can't recall what variety they are - other than they are all blue. We had a very mild winter as well - zone 7b in New Mexico.

C. divaricata ...... incana

==>>> consistent with what morz said.. these are the two types i referred to ...

i did actually walk out there and look for you yesterday .. but somehow got distracted.. and forgot.. before i could reply

ken

Does anyone have any experience with the "Dark Knight" variety? I'm wondering if it's hardy in zone 5. Also, do you know of a good reputable source for this plant? Thanks much for any advice/suggestions.

None of mine die to the ground. They all come back along the stems. I cut them back hard, but not to the ground.