Japanese Meadowsweet (Spiraea japonica)

Taxonomy

Domain	Eukarya
Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Superorder	Rosanae
Order	Rosales
Family	Rosaceae
Subfamily	Amygdaloideae
Tribe	Spiraeeae
Genus	Spiraea

Scientific Name

Spiraea japonica

Common Name

Japanese spiraea

Miller, J.H., E.B, Chambliss, N.J. Loewenstein. 2010. A Field Guide for the Identification of Invasive Plants in Southern Forests. General Technical Report SRS-119. Asheville, NC. United States Department of Agriculture, Forest Service. 126 p.

Plant

Deciduous, erect shrub to 6 feet (1.8 m) high with multiple stems and alternate branches, slender and brown, intertwining within older shaded plants or arching outward on hillside infestations. Small, alternate, lanceolate leaves with irregular serrate margins and flat-topped clusters of tiny, rose-pink flower heads that festoon branch tips and turn into crowded clusters of lustrous brown seed capsules in midsummer. Plant traits are variable due to numerous escaped cultivars.

Stem

Twigs initially whitish green, slender and wiry, usually quite hairy, jutting upward, often terminated in flower or fruit clusters. Stems becoming brown to reddish brown, round in cross section, with increasing grayish to whitish lengthwise stripes of dotted cork and protruding circular leaf and branch scars surrounded by corky deposits. Multiple basal sprouts on older plants intertwine for support.

Leaves

Alternate, thin, elliptic to lanceolate, 1 to 3 inches (2.5 to 7.6 cm) long and less than half as wide, tips are pointed and bases wedge shaped, margins irregularly and sharply serrated but less so towards the base. Blue green to green above and lighter beneath. A short petiole connects to a pronounced whitish-green midvein with about 10 lateral, curved veins that end at serrate tips and are hairy beneath.

Flowers

June to September. Terminal on new growth, multibranched, flat-topped clusters (corymbs) of many red to rosy, domed flower buds that open into tiny, whitishpink to rose (rarely white) flowers, 0.2 inch (5 mm) wide with 5 petals and an extended mist of anthers. Sepals and stalks hairy.

Fruit and seeds

July to November. Flat-topped heads of tiny star-shaped clusters of 5 smooth and lustrous, tan to brown capsules that split on top at varying times to release 1 minute golden seed, 0.09 to 0.1 inch (2 to 2.4 mm) long.

Ecology

Forms dense infestations of entangled stems and branches and produces abundant foliage to exclude other plants and impact animal habitat. Seeds are dispersed by gravity, water, and soil movement during road maintenance. Populations occur along streams, roads, and adjacent disturbed sites and move into forest gaps and understories. Infestations intensify by abundant basal sprouting. Tolerant of a wide variety of growing conditions.

Resembles

Resembles several native and nonnative spiraeas, but is unique in the flat-topped, pink to pink-rose flower clusters and brown fruit clusters, the hairy branchlets and flowers, and lanceolate leaves. It is the species most often found growing in dense infestations. The other nonnative spiraea species have yet to become so problematic.

History and use

Introduced from Japan, Korea, and China as an ornamental about 1870. Several cultivars still sold and planted by unsuspecting gardeners.

Distribution

Found as scattered dense infestations in VA, KY, TN, NC, SC, and north GA.

Management strategies

• Do not plant. Remove prior plantings, and control sprouts and seedlings. Bag and dispose of fruit in a dumpster or burn.
• Treat when new plants are young to prevent seed formation.
• Minimize disturbance within miles of where this plant occurs, and anticipate wider occupation when plants are present before disturbance.
• Do not treat with herbicides when leaves are yellow.
• Manually pull and tree wrench when soil is moist, ensuring removal of the roots.

Recommended control procedures

• Thoroughly wet all leaves with Garlon 3A or a glyphosate herbicide as a 3-percent solution (12 ounces per 3-gallon mix) in water with a surfactant. Applications may be made almost any time of year, but air temperature must be above 65 °F (18 °C) to ensure absorption by the plant. September is the best time of year for application.
• Cut large stems and immediately treat the stump tops with one of the following herbicides: a glyphosate herbicide or Garlon 3A as a 25-percent solution (3 quarts per 3-gallon mix). ORTHO Brush-B-Gon, Enforcer Brush Killer, and Vine-X are effective undiluted for treating cut-stumps and available in retail garden stores (safe to surrounding plants).

Images

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