Spiraea japonica (Japanese Spirea)

Spiraea japonica (Japanese Spirea) is a dense, broadly mounded, deciduous shrub with oval to lance shaped, sharply-toothed, bright green leaves. In late spring to midsummer, domed sprays of white to pink flowers grace the tips of the branches and contrast well with the foliage. The blossoms are followed by small capsules that are smooth and glabrous. A single plant produces hundreds of small seeds that are naturally dispersed. Heat and drought tolerant, Japanese Spirea is a popular ornamental shrub that is often grown as a flowering hedge, low screen, or foundation shrub.

Introduced into North America and Europe as an ornamental, Japanese Spirea has become naturalized and shown the potential to become an invasive weed in both North America and Europe. It can invade a variety of habitats including fields, forests, stream banks and many disturbed areas. Once established, it can form dense stands which displace native herbs and shrubs. The seeds can last for many years in the soil, making its control and the restoration of native vegetation especially difficult.

20 commonly available Japanese Spirea cultivars were evaluated for fertility using pollen and seed germination. 3 sterile cultivars were identified: ‘Crispa’, ‘Dart’s Red’, and ‘Neon Flash’. The other 17 cultivars tested, which should be treated as entirely fertile for the purposes of invasive plant management, were ‘Albiflora’, ‘Anthony Waterer’, ‘Candlelight’, ‘Dakota Goldcharm’, var. alpina ‘Daphne’, ‘Flaming Mound’, ‘Flowering Choice’, ‘Froebelii’, ‘Golden Princess’, ‘Goldflame’, ‘Goldmound’, ‘Gumball’, ‘Lemon Princess’, ‘Little Princess’, ‘Magic Carpet’, ‘Norman’, and ‘Shibori’.

Sterile cultivars can help reduce the use of fertile varieties in areas where Japanese spirea has shown the potential to become invasive.

• Grows up to 4-6 ft. tall (120-180 cm) and 5-7 ft. wide (150-210 cm).
• A full sun lover, this plant is easily grown in average, medium moisture, well-drained soils. Tolerates light shade as well as a wide range of soil conditions.
• Suitable for borders, foundation plantings, cottage gardens, banks and slopes (erosion control).
• Attracts butterflies.
• Deer-resistant.
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• Virtually pest and disease-free.
• Flowers on new wood, so prune in late winter to early spring if needed. If overgrown, can be renovated by cutting back hard immediately after flowering.
• Propagate by softwood cuttings in summer or by division in autumn or spring
• Spiraea japonica species is native to Japan. It can be an aggressive self-seeder and spread in the garden by suckering.
• Find where this species is invasive in the United States.
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