Caryopteris are notoriously late to leaf out in spring. Even in my very mild climate (where these are true shrubs, not dieback perennials), it is rare to see much happening before midMay. And that's typically why you rarely see them in nurseries early in the season.....they tend to look pretty dead :-)

Course I'm far and away from you (in the South), but mine showed new growth in mid April, about the same time most deciduous trees were leafing out). However, mine did not die back to the ground, so that may have helped.

Give them a couple more weeks. The whole northern tier of states had a horrible spring - late snowfalls, freezes and just plain cold, wet weather. That said, the only caryopteris that has persisted for me is a Worcester Gold; it is has lasted 15 years. I think the key to its longevity is the location. It is planted at the top of a slope next to a gravel walkway in a garden bed up against the house and facing east (gets full sun until about 1:00 pm). So I think if you can provide superior drainage (try mulching with gravel), especially in winter and a sheltered location protected from frost pockets and northwest winds you might get a longer lived plant.

My 'Dark Knight" here in upstate NY (5b) just started leafing out about a week ago.

My caryopteris ' Snow Fairy' just started pushing stalks a few days ago. Other front runners for "Hello, thought you were dead" are Amsonia Blue Ice,, chiothanus (Old Man's Beard) and any hibiscus syriacus. These plants are anxiety producing.

'Snow Fairy' is an entirely different type of Caryopteris (C. divaricata), a true deciduous perennial rather than a sub shrub like C. clandonensis or x clandonensis.

I have two Blue Butterflies...one was started from seed in 2016 and one started from seed in 2019. Both started showing growth last month. The older one is progressing fairly rapidly. However, the younger one, though progressing, is taking its sweet time with adding leaves. I am guessing age must influence it. I hope yours do come back!

I called them. Lost 7 of 9 (!!). D*mn! I fortunately did find replacements of this elusive "Dark Knight" -- but I am going to have to learn to take softwood cuttings to have back-up plants. I wonder if planting large plants mid-summer (July) had anything to do with it - ?. I did buy mostly small pots this time around (5 small, 2 large), maybe that will make a difference in establishment, we'll see.