Answer: Late summer or early fall are not the best times to cut back your shrubs. Pruning encourages new growth which may not have time to completely harden off before cold weather arrives which will result in dieback of all the new growth. Instead of pruning now, wait until early next spring when things just begin to grow. At that time you can cut your butterfly bush down to nearly ground level and your hydrangea to 18-24" about the ground. This renewal pruning will result in lots of healthy new growth later in the spring and early summer.
Enjoy your garden!
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