I live in NJ and pruned back my butterfly bushes the last week of March. We have had a warm spell of weather during which growth has been explosive and a couple nights last week with temperatures in the mid-30s. I am wondering if the warping I am seeing in the new leaves on my Dark Knight, pink, and blue bushes is the result of freeze damage. The leaf blade between midrib and veins looks like it is puckering, almost like a spinach leaf does. No similar damage on my bicolor bush.
Butterfly Bush Leaf Damage
Certified GKH Gardening Expert
These articles should help: https://www.gardeningknowhow.com/plant-problems/environmental/tips-for-saving-cold-damaged-plants.htm