I just became a caretaker for a cemetary. there are a lot of Spirea bushes that have not been trimmed in years. they are over 6 feet around and bigger. How do I go about trimming them to make them smaller to be able to mow around them?
Start by removing all the dead branches. Cut back all the sparse branches back to fuller green leaves. Cut back about 1/3 of the shrub at this point.
You want to help bring more sunlight into the center of the shrub.
Spireas should be trimmed at least twice a year. One trimming should occur right after blooming in the spring. Trimming will not only keep the shrub nice and full, but it will stimulate new growth on the plant. Many spireas have a bright, red new growth that at times can be almost as ornamental as the flowers themselves. Lightly trimming you spirea after blooming will extend this shrub's season of interest. The second pruning should occur in late fall or early spring. This pruning will usually be a more drastic trim.
It may take a couple of seasons to get them back to manageable size and give them a fuller look. I've seen some really ugly Spirea make a comeback!
After spirea finishes blooming, trim it back. It probably needs thinning as well since it sends up many sucker stems. Cut some of these to the ground. This results in little sunlight reaching the interior and there is often a lot of dead wood. When trimming, leave some green leaves or cut back to the ground. Do not leave shortened stems with no leaves. Do a few cuts in the top to allow more sun in the interior in hopes of getting more leaves to break inside. Spirea can also be cut to the ground in the dormant season and will come back but not flower that year. If you do this, make sure to fertilize when sizes of new growth begin.