A: In this case, the spirea was still blooming into October, and we want to stay away from pruning much of anything going into the colder months. Pruning induces growth, and that tender, new growth won’t have time to harden off before the first freeze. I’d leave it be until February or March, just prior to new spring growth emerging.
Pay close attention to when spirea blooms before taking out the shears or hand pruners. Spring-blooming spirea varieties bloom on old wood, so a good rule of thumb is always to prune back after flowering! This is the case (in most situations) with azaleas, rhododendrons, hydrangeas, and gardenias too.
Another question I received was about removing tall shoots from the top of azaleas now. I have that tall, vertical growth sprouting out of my abelias too. If you’re just removing a handful of sprouts, that will be fine this time of year.