The best time for pruning spirea would be the spring, however you can cut them back in late fall if you want to tidy up the area now.
Goldmound spirea benefit being cut back hard.

Ian

Thanks Ian.

I cut my spirea every spring. I reduce them to about one foot tall sticks, before leaves start sprouting. With no leaf sprouts, the bush uses all energy for growth, no waste. I do reduce the amount of sticks in center of bushes to allow more airflow when the leaves fill out. I remove those as low as I can cut to the ground.

With yearly haircuts, the spirea bushes give me great color, plenty of blooms each season. I think they do much better trimmed yearly, than when left alone. More able to fill out evenly, new growth has the good color, which lasts longer. Terrific bloom on these bushes.

I found the pruning recommended on many bushes and plants hard to do at first. They looked so healthy, full!! However NOT cutting, they were not as nice, bloomed less that year. Clematis is another plant that really benefits from yearly pruning, though I only cut mine down to about 3ft, never to the ground. Again, better regrowth, more flowers, develops a very healthy root system.

Yes I second the suggestion for a hard pruning on spireas yearly...I do the same to mine. I cut them to the ground (maybe 1 inch) each spring before the new leaves come out. And on clients' spireas I will prune them to the ground right after they finish flowering if I have a new client and wasn't there beforehand to do this before leafing out. This really does keep them in nice form.

With both clematis and spiraea the expected response to such treatment depends on which kind is being talked about. There are several categories of clematis growth behavior, most will not flower if whacked down every year. Likewise, many kinds of spiraeas flower in spring and will not do so if cut to near the ground every year.

My 'Goldflame' clearly hated being cut off and still shows some signs of having made a half-hearted recovery years later. However, it is in a shaded position dominated by a pin oak tree.