Spirea (Spiraea species)
Familiar, old-fashioned flowering shrubs, spireas are enjoying a well deserved resurgent popularity in residential landscapes these days. Both traditional bridal wreath types and new, compact hybrid versions of this lovely, self-reliant plant are justifiably appreciated for their delicate flowers, vigor and pest resistance. Whether they form cascades of graceful, arching branches or dense, low-growing mounds dotted with flowers they are dependable additions to the yard. After their glory days of bloom during a brief period in spring or summer, spireas are unobtrusive green background plants in the yard until they drop their leaves in the fall.
Most types of spireas will grow from down South as far north as the Great Lakes, upper New York State and along the Atlantic coast into Maine (Zone 5), where winter temperatures do not dip much below -10° to -20°F. They withstand winters even farther north if they are protected.
Size: Old-fashioned spireas can grow a gangly, arching 6 feet tall and almost that wide. However, the new hybrid types tend to be somewhat smaller, ranging from 3 to 5 feet tall and spreading more compactly from 3 to 4 feet wide.
Foliage: Spirea leaves usually have slightly toothed or lobed edges. They're narrowly oval, 1 to 4 inches long, and grow on alternate sides of the stems. Some versions have shiny bluish green to green, or yellow-green foliage. The leaves of a few, such as bridal wreath and Thunberg spirea show an autumn color before they drop.
Flowers & Fruit: Traditional spireas feature rows of showy white, one inch diameter flowers which appear in flattened clusters along the length of arching branches. Hybrid spireas may have purple, rose, or pink flowers at the tips of stems. Flowering starts in early May in northern climates but some types bloom as late as early June to July, depending on where you live. In the South flowers appear on and off during mild winter spells, but the main bloom time is February to March. The fruits are uninteresting dry pods.
Billiard spireas (Spirea x billiardii) are good for massed plantings on steep banks because they spread by underground stems;
Bridalwreath spirea (S. prunifolia ‘Plena’) is a traditional favorite introduced in 1845.
Bumald spireas (S. x bumalda) have flower colors ranging from white to dark pink and crimson.
‘Anthony Waterer,’ has rose-pink flowers.
‘Monhub,’ or Limemoundä, is very cold hardy; is only 2½ feet tall.
‘Gold Flame’ does well in the South because it tolerates heat well
‘Golden Princess’ has bronze-yellow spring foliage, pale yellow in summer; pink flowers appear almost all summer in the North.
Garland spireas (S. x arguta) have tiny white flowers and bloom more profusely than other spirea varieties.
Japanese spireas (S. japonica) are useful as ground covers.
‘Alpina’ makes a good rock garden plant.
‘Norman’ has deep red flowers and burgundy red fall foliage. ‘Shirobana’ has white, pink and red flowers all on the same plant
Nippon spirea (S. nipponica) has small, white flowers.
‘Snowmound’ does well in the South.
Reeve’s spireas (S. cantoniensis), while generally deciduous shrubs, are evergreen in parts of California and other warm-weather areas.
Thunberg spireas (S. thunbergii) have thin, feathery branchlets and clusters of tiny pure white flowers.
Vanhoutte spireas (S. x vanhouttei), also called Bridalwreath; one of the best and most widely grown spireas. Known to be drought-tolerant.