My friend Kate asked me to come by and look at her bridal wreath spireas. These plants are lush, green and over five feet tall; Kate was wondering how to prune them. She wants them to bloom more. The plants are under the eaves of the house, some facing south, and others facing west, all in filtered light from pines. There are two kinds of spireas: those such as the bridal wreath that grow on cascading branches with white flowers that bloom in the late spring to early summer; and those that are shrubby and flower with pink, white or red blooms in summer to fall. These lovely flowers attract butterflies. On the whole, bridal wreath spireas need little pruning. However, they can become tall and leggy with branches reaching beyond their planting location as Kate’s are. Pruning lightly after blooming can usually manage their size. Rather than shearing with a hedge trimmer, each branch should be cut back as close to the ground as possible, cutting out only one-third of the bush per year. Shearing just encourages a lot of new tangled growth that is unsightly and can actually damage the shrub. On bridal wreath spireas, flowers develop on branches that grew the previous summer. This means if you are pruning for more flowers for next year, you need to prune right after blooms fade in late spring. Pruning in late summer or fall will remove the new growth and reduce the number of flowers the following spring. On the other hand, if there are dead or dying branches, crossed or rubbing branches, those can be pruned out at any time. Sunset Western Garden Book recommends, “Prune bridal wreath spireas after flowers have finished; cut to the ground wood that has produced flowers.” Sometimes there is a need for a more severe rejuvenating prune to bring languishing plants back to vibrant health, similar to the kind of pruning occasionally required in lilacs. To maintain the health of the shrub it is best to manage this over a two- to three-year period taking only a third of the shrub down at a time. With renewal pruning, it will take a number of years before bridal wreath spireas have the arching, drooping flowering branches again. For shrubby spireas, removing the spent flower clusters now, may yield a second less abundant bloom. JoAnne Skelly is Associate Professor & Extension Educator, Emerita at the University of Nevada Cooperative Extension. Reach her at skellyj@unr.edu.
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