|I have two shrubs that come from my grandmother's garden. She called them|
|Pruning spirea is easy if you think about when the specific variety blooms. Those that bloom early in the spring such as Bridalwreath and Snowmound should be pruned right after they flower because they bloom on old wood. Spring bloomers are usually trimmed for shape and to contain the size. Like lilacs, they can become woody and unproductive as they age. In that case, the oldest stems can be cut out at the base of the plant to encourage new growth. Summer-blooming varieties such as all of the Spirea japonica and S. bumalda should be pruned in early spring. They bloom on new growth. To keep them full, summer-blooming varieties are often pruned back hard, removing 1/2 or more of their growth. The fading flowers of summer-blooming varieties can also be pruned off if you find them unsightly.
Best wishes with your shrubs.