The bridal wreath spirea that we enjoy in our gardens is actually the doulbe-flowered 'Plena' form of this species. Click to download a large version (800x600) of this image.
Bridal wreath spirea grows as a loose, gracefully arching shrub to around 6 ft (2 m) in height and width. The slender shiny brown stems tend to be a little zig-zaggy. It has deciduous 1-2 in (2.5-5 cm) ovate leaves with fine teeth on the margins. The leaves are glossy dark green, often turning purplish or reddish orange in autumn. The flowers are snowy white and double, about a third of an inch (0.8 cm) in diameter and produced all along the stems in open corymbs of 3-6, each cluster about 2.5 in (6 cm) across. Bridal wreath spirea blooms in early to mid spring, before the leaves come out, and a little earlier than Reeves' spirea (S. cantoniensis). The single flowered form, var. simpliciflora, is rarely seen in cultivation. Most of us know only the double flowered cultivar, 'Plena', sometimes called 'Floreplena'.
Location Spirea prunifolia var. simpliciflora, the wild form, hails from temperate Asia in Korea, eastern China and Taiwan where it grows on rocky hillsides. S. p. 'Plena', the garden form, apparently originated in Chinese gardens, and actually was discovered by Western botanists and horticulturists before the wild form was known.
Culture Light: Grow bridal wreath spirea in full sun to partial shade. In warm climates, protection from midday sun is helpful. Moisture: Bridal wreath spirea likes a good moist soil, but of course, not waterlogged. Hardiness: USDA Zones 5-9. Bridal wreath spirea needs some cold weather to flower properly, and probably will not perform well in zone 9, and especially in 9B. With protection in winter (cut to the ground and mulch), bridal wreath spirea can be grown in zone 4. Propagation: The flowers of Spiraea prunifolia 'Plena' are sterile and the plant does not set seed. However, it is easy to start cuttings of spireas. Just cut 4-8 in (10-20 cm) off the end of a young, fast growing stem tip, and insert it in a pot with damp sand or a loose potting mix. (I use clear plastic cups so I can see the roots developing.) No need for rooting hormone. Until the roots are formed, you must keep the leaves from drying out since the plant has no way to bring in water. To keep the leaves from drying, you can put the whole shebang in a plastic bag or jar, cover just the leaves with plastic, or you can mist the leaves for about 10 seconds every 10 minutes or so. (I have a fancy timer for this.) Roots should start growing in a week, and in a month or so you can pot up the little cutting in regular potting mix for another couple months before setting out in the garden.
Bridal wreath spirea isn't exactly a garden standout for most of the year but come early spring the shrub erupts into an explosion of tiny white flowers strung densely along wirey stems that toss in the breeze to become the star of the spring garden.
Bridal wreath spirea (sometimes called popcorn spirea) is an old favorite among American gardeners and a common sight in home landscapes throughout much of the eastern U.S. Use bridal wreath spirea in an informal mixed hedge, in the garden border, or as a specimen where its generous springtime bright white floral display will stand out. If left alone, bridal wreath spirea grows into a graceful, open, arching shrub with some branches drooping all the way to the ground. It should never be sheared, but may have to be pruned to keep it in its allotted space. Like other shrubs that bloom in early spring, this one should be pruned (if necessary) right after blooming. An older plant can be rejuvenated by cutting all the stems to the ground after it has bloomed.
Note that the genus, Spiraea, is not spelled the same as the common name, spirea. Bridal wreath spirea is a tough little bush and not at all fussy about soil type. This easy-to-grow flowering shrub blooms with hundreds of pure white roselike flower clusters all along gracefully arching leafless stems. Very attractive, especially when the sun shines directly on it.