Summary ⁵

Microstegium vimineum, commonly known as Japanese stiltgrass or Nepalese browntop, is an annual grass that is common in a wide variety of habitats and is well adapted to low light levels.

Biology and spread ⁶

Japanese stiltgrass is an annual grass, with all plants dying each fall. It is a colonial species that spreads during the summer and fall by rooting at stem nodes that touch the ground. Individual plants may produce 100 to 1,000 seeds that fall close to the parent plant from both self-fertilizing and cross-fertilizing flowers. Seed may be carried further by water currents during heavy rains or moved in contaminated hay, soil, or potted plants, and on footwear and vehicles. Stiltgrass seed remains viable in the soil for five or more years and germinates readily. Deer and other grazers reportedly do not browse it, though they have been found to spread the seeds. Stiltgrass leaves a thick layer of thatch after dieback each year in heavily invaded areas, and while leaves decompose quickly, stems do not. Like other invasive species, stiltgrass is physiologically adaptive. For example, it is able to withstand low light levels where nutrient levels are sufficient, and able to withstand low nutrient levels where light levels are sufficient. While stiltgrass can photosynthesize in low light conditions and respond quickly to the changing light conditions typically found on the forest floor, the very low light conditions found beneath a multilayered forest canopy will limit its growth.

Description ⁷

More info for the terms: caryopsis, presence

This description provides characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (for example, [15,71,92,128,141,164,230]).

Morphology: Japanese stiltgrass is an annual. It has a straggling to decumbent, loosely branched habit. Aerial culms are 3 to 5 feet (1-1.5 m) long [34,59,71,164]. They may be "wiry" and multibranched [56]. Japanese stiltgrass produces short to long (depending upon shading), spreading stolons. Intertwined stolons often form dense lawns. The leaves are cauline, with 0.5-inch (1 cm) wide and 3- to 4-inch (8-10 cm) long blades. The inflorescence is a 4.5 to 6 mm, terminal or axillary raceme bearing paired spikelets [34,59,71,164]. Terminal racemes bear chasmogamous flowers, while axillary racemes bear cleistogamous flowers [15]. The fruit is a 2.8- to 3.0-mm, ellipsoid caryopsis. Fruits often have twisted awns, although some fruits are awnless [34,59,71,164]. In New England collections, presence of awns varied within and among populations [58]. When present, awns are 3 to 8.5 mm long [220]. Root biomass of Japanese stiltgrass is  "remarkably small" compared to its aboveground biomass [51,53], and its roots are shallow [43,200]. A greenhouse study found that at the end of the growing season, Japanese stiltgrass roots were longest in dry (x=46 inches (18 cm)) soils compared to roots in soils of moderate (5 inches (13 cm)) and saturated (5.5 inches 14 cm)) water content. Lateral roots were few, averaging from 3 to 5 per plant [200]. Another greenhouse study found Japanese stiltgrass's roots were shallow and its root biomass was significantly less than its aboveground biomass (P<0.001), so the authors concluded Japanese stiltgrass in unlikely to access moisture in deep soil layers [200].

There has been confusion as to whether Japanese stiltgrass is sometimes perennial [50,51,124], but it is not. Mehrhoff [124] states that this confusion arose from misidentification of white grass—a morphologically similar native perennial—as Japanese stiltgrass. Japanese stiltgrass is distinguished from white grass, with which it often cooccurs, by its ciliate leaf sheath collar and paired spikelets (vs. white grass's glabrous to pubescent leaf sheath and one-flowered spikelets) [124].

Physiology: Japanese stiltgrass is adapted to low-light conditions [37,83,201]. Japanese stiltgrass uses C4 pathway photosynthesis. It is unusual for a C4 grass to photosynthesize efficiently under low light conditions, but Japanese stiltgrass is very shade tolerant 12,14,25,83,228. In the greenhouse, Winter and others [228] found Japanese stiltgrass grew well under 5% of full sunlight, and the photosynthetic rate of individual leaves was fully saturated at 25% of full sunlight. Dry-matter biomass production was similar under 18% to 100% of full sunlight. Japanese stiltgrass in the understory of a closed-canopy yellow-poplar-white oak forest in Great Smoky Mountains National Park took advantage of occasional, high-intensity sunflecks for optimal photosynthesis [83]. Best Japanese stiltgrass growth occurs on forest-grassland ecotones, where mean photosynthetically active radiation (PAR) is 35% [37]. Ueno [209] provides a description of Japanese stiltgrass's leaf physiology and cellular anatomy.

There are apparently genetic differences in shade tolerance among Japanese stiltgrass populations. Among 3 Japanese stiltgrass populations from Indiana grown in a growth chamber, 2 populations increased specific leaf area in response to shade, while the other did not [49].

Species response to increased levels of atmospheric carbon dioxide can affect plant community composition. High carbon dioxide levels may negatively affect Japanese stiltgrass compared to plant species better able to assimilate extra carbon dioxide. In field experiments in Tennessee, Belote and others [19] found that in a wet year, Japanese stiltgrass produced twice as much biomass under ambient carbon dioxide levels compared to elevated carbon dioxide levels (P=0.07). In a dry year, there was no significant difference in Japanese stiltgrass biomass between carbon dioxide treatments. In contrast, Japanese honeysuckle, a common nonnative associate of Japanese stiltgrass, produced 3 times as much biomass under elevated carbon dioxide levels in both wet and dry years [19].

Ecological threat in the united states ⁸

Japanese stiltgrass is especially well adapted to low light conditions. It threatens native plants and natural habitats in open to shady, and moist to dry locations. Stiltgrass spreads to form extensive patches, displacing native species that are not able to compete with it. Where white-tail deer are over-abundant, they may facilitate its invasion by feeding on native plant species and avoiding stiltgrass. Japanese stiltgrass may impact other plants by changing soil chemistry and shading other plants. The interaction between stiltgrass and the Northern Pearly Eye (Enodia anthedon), a member of the brush-footed butterfly family Nymphalidae, is unclear. This butterfly is rare to uncommon along the Potomac River in the Washington, DC area. Its caterpillar eats grasses. Dr. Robert Robbins, a Smithsonian entomologist and butterfly specialist takes weekly walks at Great Falls, Maryland, and made the following observations. The Northern Pearly Eye occurs uncommonly at Great Falls from May to October (maybe 2-15 individuals seen over the entire flight period). Adults were especially common during the summer of 2004. The butterfly became exceedingly common during the summer of 2005 when about 20 adults were seen during a 2 hour walk, especially in the vicinity of stiltgrass, on which a female was observed placing an egg. In May 2006, the butterfly was again common, but the population then crashed, and only 2-3 individuals were seen from June to October 2006. Further investigation is needed to study the potential impacts of stiltgrass on this and possibly other butterflies or other insects that utilize stiltgrass as an alternative host plant.

History in the united states ⁹

First documented in Tennessee around 1919, stiltgrass may have accidentally escaped as a result of its use as a packing material for porcelain.

Key plant community associations ¹⁰

More info for the terms: alliance, cover, forbs, graminoid, hardwood, litter, mesic, nonnative species, presence, shrub, shrubs, succession, swamp, vine, vines

Japanese stiltgrass is mostly associated with forest edges, wetlands, and disturbed areas throughout its US distribution [15]. Shade, low elevation, and moist to mesic soils are important for successful Japanese stiltgrass invasion, with overstory type apparently less important in determining Japanese stiltgrass presence or absence 137.
In its native range, Japanese stiltgrass grows mostly in riparian and mesic areas, being common along shady riverbanks in broadleaved forests [220].
Japanese stiltgrass is often associated with several other nonnative species in the United States. It is frequently found with garlic mustard (Alliaria petiolata) in the East and Southeast ([127]; also see the Vegetation classifications list below). Japanese honeysuckle (Lonicera japonica) is often consistently associated with Japanese stiltgrass in the Great Lakes and eastern regions of the United States. In a southern Illinois oak-hickory forest, for example, Japanese stiltgrass cooccurred with Japanese honeysuckle and was also associated with nonnative sericea lespedeza (Lespedeza cuneata) and multiflora rose (Rosa multiflora) [68]. Japanese barberry (Berberis thunbergii) commonly cooccurs with Japanese stiltgrass across Japanese stiltgrass's distributional range [174]. In New Jersey, Japanese stiltgrass and Japanese barberry grew together in a bottomland oak-American beech-sweet birch (Quercus spp.-Fagus grandifolia-Betula lenta) forest [53]. Japanese stiltgrass is sometimes associated with Norway maple. In red maple forests of New Jersey, Japanese stiltgrass dominated the ground layer of sites where Norway maple had replaced red maple as the overstory dominant [129].
The following descriptions provide information on where Japanese stiltgrass is known to be present, invasive, or likely to be invasive based
upon current knowledge of Japanese stiltgrass's habitat preferences. Japanese stiltgrass is likely invasive or dominant in more plant communities than those described below
Great Lakes and Northeast:
Japanese stiltgrass occurs in pine (Pinus), oak (Quercus)-pine, oak-hickory (Carya), and mixed-hardwood woodlands and forests in these regions. In recently burned, mixed-mesophytic woodlands of southern Illinois, overstory codominants of Japanese stiltgrass-infested sites included river birch (Betula nigra), black walnut (Juglans nigra), sycamore (Platanus occidentalis), black cherry (Prunus serotina), and winged elm (Ulmus alata). Philadelphia fleabane (Erigeron philadelphicus), clammy groundcherry (Physalis heterophylla), fragrant bedstraw (Galium triflorum) and drooping woodreed (Cinna latifolia) cooccurred with Japanese stiltgrass in the ground layer [7]. Overstory codominants in a southern Illinois black oak-post oak (Q. velutina-Q. stellata) forest in early old-field succession included eastern redcedar (Juniperus virginiana), flowering dogwood (Cornus florida), sassafras (Sassafras albidum), and common persimmon (Diospyros virginiana). Coralberry (Symphoricarpos orbiculatus), poison-ivy (Toxicodendron radicans), and nonnative Japanese honeysuckle were commonly associated understory species. Herbs associated with Japanese stiltgrass in the ground layer included big bluestem (Andropogon gerardii), golden alexanders (Zizia aurea), and blunt-lobe woodsia (Woodsia obtusa) [68].
In New Jersey, Japanese stiltgrass occurred in red oak-black oak-chestnut-white oak (Q. rubra-Q. velutina-Q. prinus-Q. alba) and white ash-sweet birch-American beech (Fraxinus americana-Betula lenta-Fagus grandifolia) forests. It was less common on sites with high cover of overstory oaks and understory
blueberries (Vaccinium spp.) than in other hardwood forest types [100]. Overstory associates of Japanese stiltgrass in a sugar maple-red maple (Acer saccharum-A. rubrum)-sweet birch forest in New Jersey included shagbark hickory (C. ovata), bitternut hickory (C. cordiformis), and American elm
(U. americana). The most common shrubs included black haw (Viburnum prunifolium), spicebush (Lindera benzoin), and multiflora rose. Although Japanese stiltgrass was the most common groundlayer species, jack-in-the-pulpit (Arisaema vimineum) frequently cooccurred in the ground layer [210].
In Maryland, Japanese stiltgrass occurred in the ground layers of Virginia pine-southern red oak (Pinus virginiana-Q. falcata) communities. Yellow-poplar
(Liriodendron tulipifera), red maple, hickory (Carya spp.), and black cherry were associated in the overstory [27]. In Maryland and Virginia, Japanese
stiltgrass was a component of mixed oak-sweetgum-swamp tupelo (Quercus spp.-Liquidambar styraciflua-Nyssa
sylvatica var. biflora) communities on the inland coastal plain of Chesapeake Bay [170].
Appalachians:
Japanese stiltgrass is common in low-elevation oak-pine forests of the Piedmont [90,171,172]. In Cumberland County, Pennsylvania, Japanese stiltgrass occurred in a red maple/spicebush/skunk cabbage-sphagnum (Symplocarpus foetidus-Sphagum spp.) swamp [112]. Romagosa and Robinson [172] provide a comprehensive list of shrub, vine, and herbaceous associates of Japanese stiltgrass in an upland loblolly pine (P. taeda)-mixed
oak forest on piedmont sites in Pennsylvania. The federally endangered [208] glade spurge (Euphorbia purpurea) cooccurred with Japanese stiltgrass in the forest's groundlayer vegetation [112].
Japanese stiltgrass is reported in mixed-hardwood and riparian communities in Kentucky. In mixed-hardwood forest in the Cumberland Mountains, overstory species associated with Japanese stiltgrass included northern red oak (Q. rubra), white oak, yellow-poplar (Liriodendron tulipifera), Virginia pine, sugar maple (Acer saccharum), basswood (Tilia heterophylla), American beech, and yellow buckeye (Aesculus octandra). Common shrubs and vines were strawberry-bush (Euonymus americana), hillside blueberry (Vaccinium pallidum), Virginia creeper (Parthenocissus quinquefolia), and common greenbrier (Smilax rotundifolia). At 9% to 35% cover, Japanese stiltgrass was the most common graminoid. Associated grasses and forbs included mannagrass (Glyceria spp.), slender muhly (Muhlenbergia tenuiflora), white snakeroot (Ageratina altissima), and panicledleaf ticktrefoil (Desmodium paniculatum) [165]. Along the Blue River of Kentucky, Japanese stiltgrass occurred in a big bluestem-indiangrass (Sorghastrum nutans) prairie on gravel wash [81]; the federally endangered [208] Short's goldenrod (Solidago shortii) also occurred in the gravel-wash prairie community [81].
Southeast and South:
In the Southeast, Japanese stiltgrass often occurs upland from or in dry portions of wet grasslands [187]. On a North Carolina floodplain, Japanese stiltgrass and Japanese honeysuckle comprised nearly 100% of the ground layer and understory of a boxelder-green ash (Acer negundo-Fraxinus pennsylvanica)-sycamore forest [12].
On the George Washington Memorial Parkway in Virginia, Japanese stiltgrass occurred in the ground layer of old-growth oak-hickory forest. Dominant trees include white oak, scarlet oak (Q. coccinea), and chestnut oak, shagbark hickory, and mockernut hickory (C. tomentosa). Shrub associates included mountain-laurel
(Kalmia latifolia), pink azalea (Rhododendron periclymenoides), and black huckleberry (Gaylussacia baccata). Groundlayer
herbaceous associates were winter bent grass (Agrostis hyemalis), broomsedge bluestem (Andropogon virginicus), common velvet grass (Holcus
lanatus), and white clover (Trifolium repens). Lianas were common in the forest and included
trumpet-creeper (Campsis radicans), Oriental bittersweet (Celastrus orbiculatus), Japanese honeysuckle, and summer grape (Vitis aestivalis) [222].
Japanese stiltgrass dominates some deciduous forests of the South. In the Whitehall Experimental Forest, Georgia, Japanese stiltgrass formed a continuous lawn in the ground layer of a red maple-white oak-sycamore forest. The understory was depauperate [20]. In surveys across west-central Georgia, Japanese stiltgrass was detected in 15 of 18 watersheds. Japanese stiltgrass and nonnative species in general were more common in or near urban-rural interfaces, but Japanese stiltgrass was also common in rural locations. Cover of Japanese stiltgrass and Chinese privet (Ligustrum sinense) was negatively correlated with overall species richness and overstory reproduction (r= -0.18, P=0.003) for both variables) [113].
Vegetation classifications describing plant communities in which Japanese stiltgrass dominates the groundlayer are listed below alphabetically.
Arkansas

• Japanese stiltgrass is a local dominant in low-lying areas of loblolly pine-sweetgum forests throughout National Forests of Arkansas [134]

Louisiana

• local dominant in low-lying areas of loblolly pine-sweetgum forests on the Kisatchie National Forest [133]

North Carolina

• local dominant in low-lying areas of American beech-white oak forests on the Croatan National Forest [136]


• Guilford Courthouse National Military Park

• Delaware Water Gap National Recreation Area

• successional Virginia pine/eastern redcedar/Japanese barberry-multiflora rose/annual vernalgrass-Japanese stiltgrass forest vegetation type


• sycamore-boxelder-black walnut/silver maple (Acer saccharinum)/garlic mustard-spreading sedge (C. laxiculmis)-Japanese stiltgrass
  forest vegetation type [157]

• successional Virginia pine/eastern redcedar/Japanese barberry-multiflora rose/annual vernalgrass-Japanese stiltgrass forest vegetation type


• sycamore-boxelder-black walnut/silver maple/garlic mustard-spreading sedge-Japanese stiltgrass forest vegetation type [157]

• dry white oak-black oak-yellow-poplar/flowering dogwood/Japanese stiltgrass forest alliance


• successional black walnut-American elm/spicebush/Japanese stiltgrass forest alliance


• yellow-poplar/red maple-white ash/spicebush/Japanese stiltgrass forest alliance


• red maple-green ash/red maple/Japanese stiltgrass palustrine forest alliance [161]

• dry chestnut oak-black oak/sweetgum/Japanese stiltgrass, silver maple/poison-ivy/Japanese stiltgrass floodplain forest type


• yellow-poplar-black oak/red maple/ flowering dogwood/Japanese stiltgrass forest type


• sycamore-boxelder/spicebush/Oriental bittersweet/Japanese stiltgrass riverine floodplain forest type


• black cherry/yellow-poplar-red maple/box elder/Japanese stiltgrass-garlic mustard forest type [162]

Tennessee

• red maple-white ash/Japanese stiltgrass seasonally flooded forest vegetation type of Great Smoky Mountains National Park [199]


• boxelder/osage-orange (Maclura pomifera)/Chinese privet/Japanese stiltgrass riparian forest community type at Stones River National Battlefield [138]

Texas

• often a dominant groundlayer species in low-lying loblolly pine-sweet gum "seminatural" (secondary) forests near Gulf Coast prairies and marshes of eastern Texas [132]

Virginia

• red maple-eastern white pine/Canadian clearweed (Pilea pumila)/Japanese stiltgrass plant associations in headwater floodplains and red maple/Virginia creeper
  (Parthenocissus quinquefolia)/Japanese stiltgrass-arrowleaf tear-thumb plant associations in riparian depressions throughout the state [159]


• Appomattox Court House National Historical Park
  

• tree-of-heaven (Ailanthus altissima)-loblolly pine/Japanese stiltgrass forest alliance


• loblolly pine-white oak-southern red oak/Japanese stiltgrass forest alliance; without Japanese stiltgrass, litter layer of this and other pine communities in the Park is typically sparse


• disturbed calcareous forest alliances (oaks, pines, yellow-poplar are typical overstory dominants)


• American beech-white oak-yellow-poplar/Japanese stiltgrass forest alliance


• black walnut/wingstem (Verbesina alternifolia)-Japanese stiltgrass forest alliance


• yellow-poplar-loblolly pine/Japanese stiltgrass forest alliance


• sweetgum-yellow-poplar/Japanese stiltgrass forest alliance


• coastal plain or piedmont small-stream floodplain forest alliances (sweetgum-red maple-yellow-poplar is typical of overstory)


• red maple-sycamore/Japanese stiltgrass disturbed seep swamp alliances [150]

• dominant groundlayer species in successional eastern redcedar woodland alliance


• dominant groundlayer species in silver maple-boxelder forest alliance


• dominant groundlayer species in temporarily flooded sweetgum-yellow-poplar forest alliance [195]

• loblolly pine-sweetgum/Japanese stiltgrass seminatural forest type


• willow oak-pine oak-swamp chestnut oak/common greenbrier (Smilax rotundifolia)/Japanese stiltgrass coastal floodplain and piedmont floodplain forest types


• yellow-poplar-white oak-willow oak (Q. phellos)/Japanese honeysuckle/Japanese stiltgrass forest type


• sweetgum-yellow-poplar/spicebush/Japanese stiltgrass forest type


• locally dominant in low-lying areas of American beech-white oak/American holly (Ilex opaca) forest type [152]

Sources and Credits

1. (c) Christopher Tracey, some rights reserved (CC BY-NC-SA), uploaded by Christopher Tracey
2. (c) NY State IPM Program at Cornell University, some rights reserved (CC BY), https://www.flickr.com/photos/99758165@N06/19062844551/
3. (c) Dendroica cerulea, some rights reserved (CC BY-NC-SA), https://www.flickr.com/photos/dendroica/7852994736/
4. (c) John Brandauer, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/91753832@N00/4648826862
5. Adapted by Jonathan (JC) Carpenter from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Microstegium_vimineum
6. (c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22948726
7. Public Domain, http://eol.org/data_objects/24632564
8. (c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22948722
9. (c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22948725
10. Public Domain, http://eol.org/data_objects/24632563

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