A hardy, fast-growing shrub, spirea, or bridal's wreath (Spiraea spp.) grows to a height of 6 to 10 feet but can spread up to 20 feet wide. They grow in sun or partial shade and are tolerant of all types of soil as well as urban conditions. The classic bridal's wreath bush is the variety 'Vanhoutte,' which produces masses of clusters of small white flowers in spring. Japanese varieties (Spiraea japonica var.) grow much shorter and usually have pink flowers. A notable Japanese variety called 'Shirobana' produces white, pink and red flowers on the plant all at the same time. 'Shirobana' grows only 2 to 3 feet high.
Remove any branches that are dead, diseased, growing across or rubbing against another branch.
Remove the oldest and any weak canes or branches by cutting them off at ground level with the pruning clipper. Use the saw if the branches are large in diameter.
Thin out the remaining canes, removing about one-fifth to one-fourth of their total number. This will give the remaining canes room to develop and send out vigorous new growth that will eventually produce flowers.
Prune off dead flower heads after the shrub has finished blooming. Japanese varieties, which bloom on the current year's wood, often produce a second, smaller flush of bloom when the flower heads are promptly removed, according to Clemson University Extension.