Q.butterfly bushes
I
planted a bush 2yrs. ago. last year I trimmed the dead branches off and it grew but not as high as the year before. This year I trimmed the dead branches off but nothing seems to be growing yet. How can you tell if its dead or not? Bob
If you are seeing no new growth, it may have died off over winter.
I have seem the same results in my own garden over the past 10 years. Beautiful plant, full of blossoms, and a plant that only winters over a couple of years before if dies off.
Give it a bit more time to see if it can grow up from the roots. If you see no new growth, I would dig it up and seek a replacement.
https://www.gardeningknowhow.com/ornamental/shrubs/butterfly-bush/butterfly-bush-care.htm