Common Name: Japanese Spiraea
Scientific Name: Spiraea japonica L.
Japanese spiraea is one of more than eighty species of spiraea found in the temperate region of the northern hemisphere. Most of the species have been introduced into cultivation and are popular garden shrubs planted for their decorative flowers. It belongs to the Rosaceae (Rose) family.
Japanese spiraea is a perennial deciduous shrub. It is adapted to disturbed areas and commonly found along streams and rivers. Each plant produces hundreds of small seeds that are naturally dispersed by water and deposited along stream banks where arboreal competition is limited. Seeds distributed with fill dirt establish new populations that may expand rapidly in the highly disturbed soil of construction sites.
Origin and Distribution
Japanese spiraea is native to Japan and was first cultivated in 1870. Introduced as an ornamental landscape plant, spiraea spread from the northeast U.S. and is naturalized in much of the southeast and Midwest, including Tennessee.
There are two native species of spiraea that are similar to Japanese spiraea:S. viginiana (Britt.) and S. betulifolia (Pallas). Both of these species are rare in Tennessee; S. viginiana is listed as a threatened species by the U.S. Fish and Wildlife Service. Japanese spiraea is distinguished by dense pubescence on the branchlets and inflorescence, lanceolate leaves, and pink flowers.
Spiraea will tolerate a wide range of edaphic conditions. It grows well in full sun but may endure partial shade. Ideal habitats include riparian areas, successional fields, roadsides, power line rights of way, and forest edges. Once established, spiraea grows rapidly forming dense stands that may invade canopy gaps and defoliated areas of adjacent woodlands.
Mowing/Cutting: This method is appropriate for small initial populations or environmentally sensitive areas where herbicides cannot be used. Repeated mowing or cutting will control the spread of spiraea, but it may not eradicate it. Stems should be cut at least once per growing season prior to seed production and as close to ground level as possible.
Foliar Spray Method: This method should be considered for large thickets of Japanese spiraea where risk to non-target species is minimal. Air temperature should be above 65°F to ensure absorption of herbicides.
Glyphosate: Apply a 2% solution of glyphosate and water plus a 0.5% non-ionic surfactant to thoroughly wet all leaves. Use a low pressure and coarse spray pattern to reduce spray-drift damage to non-target species. Glyphosate is a non-selective systemic herbicide that may kill partially-sprayed non-target plants.
Triclopyr: Apply a 2% solution of triclopyr and water plus a 0.5% non-ionic surfactant to thoroughly wet all leaves. Use a low pressure and coarse spray pattern to reduce spray-drift damage to non-target species. Triclopyr is a selective herbicide for broadleaf species. In areas where desirable grasses are growing under or around spiraea, triclopyr can be used without non-target damage.
Cut Stump Method: This control method should be considered when treating individual bushes or where the presence of desirable species preclude foliar application. This treatment is effective as long as the ground is not frozen.
Glyphosate: Horizontally cut spiraea stems at or near ground level. Immediately apply a 25% solution of glyphosate and water to the cut stump making sure to cover the entire surface.
Triclopyr: Horizontally cut spiraea stems at or near ground level. Immediately apply a 25% solution of triclopyr and water to the cut stump making sure the entire surface is covered.
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