Spiraea

Fundamental Facts

HARDINESS: Zones 4 to 8
PREFERRED SOIL pH: Adaptable
PREFERRED SOIL TYPE: Average
PREFERRED LIGHT: Sun lo partial shade
ATTRIBUTES: Graceful while, pink, or red flowers; for specimens, hedges, beds
SEASON OF INTEREST: Spring to fall
FAVORITES: Bridalwreath, Vanhoutte spirea; S. joponica 'Shibori', 'Goldflame'
QUIRKS: Plants can bounce bock from winter damage, neglect, and overpruning
GOOD NEIGHBORS: Azalea, euonymus, iris, juniper
WHERE IT GROWS BEST: Thrives in a range of climates and soils
POTENTIAL PROBLEMS: Occasionally aphids
PRUNING: Lives for decades; type and time of pruning depends on variety
CRITTER RESISTANCE: Good
SOURCE: Nursery plants
DIMENSIONS: 3-5 ft (1-1.5 m) tall and equally wide

Spirea in the Landscape

Spireas are a varied group of plants grown for their attractive foliage, graceful habit, and charming flower dusters, which have small, slightly fuzzy flowers in white, pink, and red. While there are many species and cultivars, there are basically only two types: those that bloom in spring to early summer and those that bloom in summer. Both share a care-free nature and are very easy to grow.

Spireas are also easy to use in the landscape.They make a valuable addition to foundation groupings, especially when planted among shrubs with dark foliage, which highlights spireas' soft flower colors. Mound-
forming types make a neatly shaped filler for shrub and flower borders or can be massed as a groundcover. Those with arching habits make graceful specimens and are dense enough to be grouped into a hedge.

Sorting Through Spireas

Two spring bloomers have been popular for centuries because of their elegant fountain shape and profuse flowers. Both bridalwreath (Spiraea prunifolia) and Vanhoutte spirea (S. x vanhouttei) have 5-6 ft (1.5-1.8 m) long arched stems studded with white flowers. They are also quite cold tolerant, being hardy to Zone 4.
The leading summer bloomer is Japanese spirea (S. japonica), a compact, mounding shrub that usually grows 3-4 ft (1-1.2 m) tall and equally wide. The plants are covered with airy clusters of dusty pink flowers framed by pointed. 3 in (7.6 cm) long leaves with serrated edges.

Varieties grown for their flowers include 'Anthony Waterer', an old favorite with crimson blossoms, and 'Shibori', which produces white, pink, and rose flowers in the same cluster. Other Japanese spirea are valued for their foliage as well. 'Gold-flame' and 'Candlelight' have yellow leaves contrasting with pink flowers.

Growing Spirea

Spireas grow quickly when planted in early spring. Amend planting holes with organic matter, such as compost or leaf mold, and set plants at the same depth at which they grew in their containers. In alkaline soils, also work a small handful of garden sulfur into planting holes. Spireas need slightly acidic conditions; if the pH is too high, green-leaved types will develop yellow leaves. After planting, cover the root area with a 3 in (7.6 cm) layer of mulch to retard evaporation from soil. Water as needed to keep it barely moist the first season.

Once they are established, bridal-wreath types need no special care. Japanese spirea benefits from a light feeding with an organic or timed-release balanced fertilizer each spring Aphids may occasionally infest plants, but these sap-sucking insects can be knocked off foliage with a strong spray of water or apply insecticidal soap as directed on the label.

Pruning in Season

Neither type of spirea demands attentive pruning, but it's important to preserve flower buds when grooming the plants. Spring bloomers set flowers on old wood, so the best time to prune is after the flowering period has ended.To maintain the natural arching shape, prune out old woody stems near the base of die plant. Then thin crowded stems by cutting them back to various lengths for a more natural appearance.
Japanese spirea blooms on new wood, so you can prune as much or as little as you like in early spring, just as the plants begin to develop new leaves. In cold climates, prune stems damaged over winter to the ground.