If you’re looking for a lavish, flourishing shrub, the genus spirea (Spiraea) is an obvious go to. We would like to take a closer look at the multifaceted Spirea and provide you with some planting and care tips.
There are around 90 different species of Spirea (Spiraea) in the spirea plant genus. These are deciduous shrubs. The genus Spiraea belongs to the Rosaceae family and is native to the temperate climate zones of the northern hemisphere. There are around 70 species in China alone. There is a whole range of attractive, flowering Spirea which are also winter-hardy at cooler latitudes and can be used in a variety of ways in the garden.
Appearance and Growth
Spiraea grows thickly branched and compact, either tightly upright or in a funnel shape with overhanging branches, depending on the type. The species Japanese spirea (Spiraea japonica) grow as a hemispherical dwarf shrub which only grow to approx. 20 to 40 inches tall. Other species, such the Garland Spirea (Spiraea x arguta) or the Vanhoutte spirea (Spiraea x vanhouttei) can reach up to two meters tall.
Spirea already start growing shoots early on in the year. The foliage is simple and usually short stalked. It is positioned alternately on branches and the margin is often serrated or even lobed. In addition to the purely green-leafed Spirea, there are also varieties with yellowish-green foliage, such as ‘Golden Princess’, several also have beautiful fall foliage.
Spirea flowers appear lavish as the inflorescences are very densely distributed across the entire previous year’s shoots. The flowers stand on the shoots in panicles or cymes. The small, round individual flowers have five sepals and five petals and are generally white, more rarely pink colored. They have 15 to 60 stamens. Depending on the species, the flowering period is in spring from April or in summer from June. Small aggregate follicle fruit develops which is frequently twisted. This is also what the name of the plant refers to. Spirea comes from the Greek ‘speira’, meaning ‘wind, winding’.
Location and Soil
Spirea like a sunny to slightly shady location with moist, permeable and nutrient-rich soil. Important to know: The sunnier the location, the more lavish the flowers. The plants do not readily tolerate too much lime in the soil or dryness.
The Robust Spirea can be planted in containers all year round, although - as with many other ornamental shrubs - the fall is considered the best planting time. Dig a planting hole which is at least twice the size of the root ball and loosen the bottom of the planting hole. In heavy soils, a thin gravel layer at the bottom of the planting hole ensures better water permeability. Pat the soil down well after planting and water thoroughly. A mulch layer ensures that the moisture does not evaporate too quickly.
Spirea are easy-care in suitable locations. They should be regularly watered for the first year after planting. Mulching the planting space also helps to retain the moisture in the soil.
Summer bloomers such as the Japanese Spirea should be heavily pruned back in early spring. This promotes strong new shoots and a luxurious bloom in the summer. Spirea which bloom in the summer, such as the bridal wreath, should be thinned out every two to three years after flowering. This means, cutting older shoots, but not more than a third of all shoots, at the base, so that the plants regularly rejuvenate.
Overwintering or Winter Protection
At temperate latitudes, spirea are winter-hardy and do not require additional winter protection.
Spirea can be used in various ways in the garden and, due to their compact growth, are also well suited for smaller gardens. The taller, shrubby growing Spirea are well suited to free growing, informal hedges. The low, spherical Spirea can be planted in small groups in combination with decorative grasses and shrubs, or as a low hedge. They can also be used flat as groundcover or as permanent planting in containers. If you want to use flowering branches in a vase, you should cut these before they blossom.
Important Species and Varieties
Spirea are some of the most widespread ornamental woody plants in our gardens - and that’s not surprising: they are undemanding, robust and also lavish flowering. The Spirea genus can be roughly subdivided into two groups: the early blooming species, which already show their blossoms in April/May, and the summer bloomers, which bloom from June until even as late as September. The spring bloomers include the bridal wreath (Spiraea x arguta), the Grefsheim spirea (Spiraea x cinerea) and the Vanhoutte Spirea (Spiraea x vanhouttei). The Japanese Spirea (Spiraea japonica) bloom later in the year, as well as the gardener’s favorite variety ‘Anthony Waterer’ (Spiraea x bumalda). This variety, which is also widespread as Red Summer Spirea, is a hybrid of Spiraea albiflora and Spiraea japonica and is a delight in the summer months with its ruby red flowers. With a growth height of 24 to 31 inches, it is suitable for low, informal hedges. The flowers are also a very popular destination for beneficial flying insects.
Spiraea can also be readily propagated using cuttings in spring. For this, use an approx. 6 inch long, semi-hardwood shoot. Propagation is also possible through layering. In the fall, you can also propagate your spirea using hardwood cuttings.
Diseases and Pests
The Robust Spirea are non-sensitive to diseases and pests.