Answer: Butterfly bush or Buddleia can sometimes suffer hard winter damage and die back to the ground, and will then regrow from the roots or from very low on the plant. Sometimes a very bad winter or one with quickly oscillating temperatures will kill it outright. This may be what happened to yours. In my experience these shrubs tend to deteriorate after a few years and may need to be replaced with a younger more vigorous plant. I suspect the harsh winters just eventually exhaust it. In the meantime, prune off any dead wood, keep it well watered (moist but not soppng wet) and topdress with a good quality compost and/or apply a general purpose fertilizer such as 10-10-10 per the label instructions. If it has not leafed out and come into good growth by now, I think you probably do need to replace it. I'm sorry.
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