NATIVE
RANGE
Japan, Korea and China
DESCRIPTION
Japanese spiraea, also called
Japanese meadowsweet, is a perennial, deciduous shrub that grows to
4 or sometimes 6 feet in height and about the same in width. It has slender
erect stems that are brown to reddish-brown, round in cross-section and sometimes
hairy. The leaves are generally egg-shaped, 1-3 inches long, have toothed
margins and alternate along the stem. Clusters of attractive, rosy-pink flowers
are borne at the tips of branches. Seeds, measuring about 1/10 inch in length,
are contained in small lustrous capsules. Japanese spiraea is naturally variable
in form and there are many varieties of it in the horticultural trade.
ECOLOGICAL THREAT
Japanese spiraea can
rapidly take over disturbed areas. Growing populations creep into meadows,
forest openings, and other sites. Once established, spiraea grows rapidly
and forms dense stands that outcompete much of the existing native herbs
and shrubs. Seeds of Japanese spiraea last for many years in the soil, making
its control and the restoration of native vegetation especially difficult.
DISTRIBUTION
IN THE UNITED STATES
Japanese spiraea is now naturalized throughout
much of the Northeast, Southeast and Midwest.
HABITAT IN THE UNITED STATES
Japanese
spiraea is adapted to disturbed areas, tolerates a wide range of soil conditions
and grows in full sun to partial shade. It is commonly found growing along
streams and rivers, forest edges, roadsides, and in successional fields and
power line right-of-ways.
BACKGROUND
Japanese spiraea was introduced
into the United States as an ornamental landscape plant and first cultivated
in the northeastern states around 1870.
BIOLOGY & SPREAD
A single Japanese
spiraea plant produces hundreds of small seeds that are naturally dispersed
by water and deposited along stream banks. Seeds may also be carried in fill
dirt and establish new populations in the highly disturbed soil of construction
sites.
MANAGEMENT OPTIONS
Cutting
or mowing Japanese spiraea shrubs may be effective for small, initial populations
or for environmentally sensitive areas where herbicides cannot be used. Repeated
mowing or cutting will control the spread of spiraea, but will probably not
eradicate it.
Spiraea resprouts after cutting, making repeated
cutting necessary to exhaust the plants energy reserves. Stems should be
cut at least once per growing season, prior to seed production, and cut as
close to ground level as possible.
Chemical
Foliar herbicide applications
should be considered for large thickets of Japanese spiraea where the risk
to non-target
plants
is determined to be minimal. Applications may be made almost any time of
year, as long as the air temperature is above 65ºF, to ensure absorption
of the chemical by the plant. Apply a 2% solution of glyphosate (e.g., Roundup
or Rodeo®) or triclopyr (Garlon) and water plus a 0.5% non-ionic surfactant
to thoroughly wet all leaves. Use low pressure and a coarse spray pattern
to reduce spray-drift to non-target species. NOTE: Glyphosate is a non-selective
systemic herbicide that may kill even partially sprayed plants. Triclopyr
is a selective for broadleaf species. In areas where desirable grasses
are growing under or around spiraea, triclopyr can be used without damage
to the grasses.
USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS.
NOTICE: MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.
CONTACTS
For more information on
the management of Japanese spiraea, please contact:
- Kris Johnson, Great Smoky Mountains
National Park, Gatlinburg, TN
SUGGESTED ALTERNATIVE PLANTS
Some suitable
native alternatives for Japanese spiraea include shrubs like sweetfern
(Comptonia peregrina), arrowwood (Viburnum dentatum), Summersweet
clethra (Clethra alnifolia),Virginia sweetspire (Itea
virginica), silky dogwood (Cornus amomum), inkberry (Ilex
glabra), pinxterbloom azalea (Rhododendron periclymenoides), and sweetbay
magnolia (Magnolia virginica). You may wish to contact the native plant
society in your state for more assistance.
OTHER LINKS
AUTHOR
Tom Remaley, Great Smoky Mountains National
Park, Gatlinburg, TN
EDITOR
Jil M. Swearingen, National Park Service, Washington,
DC
REFERENCES
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23(1):57-61.
Chamberlain, S. 1983. Hedges, screens
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Dirr, M.A. 1986. Spiraeas of the japonica
group are summer garden aristocrats. American Nurseryman 163:54-56.
Dirr, M.A. 1990. Manual of woody landscape
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and uses. Stipes Publishing Co. Pp. 803-805.
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Komazaki, S. 1983. Overwintering of the
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Marczynski, S. 1977. The chemical defoliation
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of vascular flora of the Carolinas. Chapel Hill, NC: The University of North
Carolina Press, 1183.
Rehder, A. 1986. Manual of cultivated
trees and shrubs. Portland, OR: Dioscorides Press, 996.
Swanson, R.E. 1994. A field guide to the
trees and shrubs of the southern Appalachians. Baltimore, MD: John Hopkins
University Press, 399.
Wiesner, M.B. 1994. Virginia spiraea.
American Horticulturist 73 (August 1994): 9.
Williamson, M.A.; Bernard, E.C. 1988. Life
cycle of a new species of Blumeriella (Ascomycotina: Dermateaceae), a leaf-spot
pathogen of Spiraea. Canadian Journal of Botany 66(10): 2048-2054.
Plant Conservation
Alliance, Alien Plant Working Group.
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