As with other late-spring flowering shrubs, prune"Goldmound" spirea in late winter to early spring before new growth begins. 1 Wipe the blades. Oct 25, Spirea shrubs respond well to pruning. In the spring, after the first blooms are spent, cut the dead flowers back by trimming spirea’s stem tips back to the topmost leaf on each stem. Throughout the summer, the plants shape can be maintained by cutting back overgrown spirea shoots or stems as well as any dead or diseased branches.
Mar 02, Trim straight across the top of the plant, and when you release the rope you’ll have a perfectly rounded spirea. The two main trimming periods, in early spring and after blooming, are most important to do each year, but you can also trim your spirea as. Folks on this forum said I should do rejuvenation pruning on them.
I did, cutting them to about 10". In no time they put on new growth and looked wonderful. I highly recommend this. Also, after I'd completed the pruning and could see the bases clearly, I discovered quite a few small plants that had rooted themselves. Pruning is only needed to remove damaged or dead branches or in case you want to keep them as small as possible. Pruning during the first two seasons will help make the shrub thick instead of leggy. Deadhead after blooming to promote more flowering.
If you do not deadhead, they fade quickly and do not detract from the beauty of the plant.