Photo credit: Rebekah D. Wallace, University of Georgia, Bugwood.org
Japanese Stilt Grass
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Species at a Glance
Japanese stilt grass is an annual, herbaceous, sprawling grass that resembles miniature bamboo. It germinates in the spring and grows slowly through the summer months, reaching a canopy height of 30-61 cm (12-24 in).
Leaves: Pale green leaf blades are 3-8 cm (1.2-3.1 in) in length. They are narrow, asymmetrical, taper at both ends, and are lightly hairy, alternating along a branched stalk. A distinguishing characteristic is a pale silvery stripe of reflective hairs along the midrib of the upper surface.
Flowers: Flattened, trapezoid-shaped flowers grow in spikes on slender stalks about 3-8 cm (1.2-3.1 in) long in late August to September.
Fruits/Seeds: Dry fruits called achenes are produced soon after flowering, usually in early October.
Stems/Roots: The weak, somewhat reclining stems are hairless and branched, rooting at the lower nodes.
The native perennial whitegrass (Leersia virginica) is similar to Japanese stilt grass, but it lacks the silver stripe along the midrib and it flowers earlier in August. The nodes of stilt grass are also smooth, while whitegrass has hairy nodes. In the fall, stilt grass turns yellow to pale purple, while whitegrass stays green.
Japanese stilt grass occurs in a wide variety of habitats, including moist soils of open woods, floodplain forests, wetlands, fields, roadsides, ditches, utility corridors, and gardens. It readily invades areas subject to disturbances such as mowing, tilling, foot traffic, and flooding.
This species spreads by roots that grow from nodes along the stems that come in contact with the ground. It also spreads through a high production of seeds that disperse by water currents during floods, or by contaminated materials, such as hay, soil, and potted plants, or on footwear. Seeds can remain viable for five or more years before they germinate.
Native to Japan, Korea, China, Malaysia, and India, Japanese stilt grass was introduced into the United States in 1919 due to its use as a packing material for porcelain. It is now invasive in several states and has invaded all states in the Mid-Atlantic region.
Note: Distribution data for this species may have changed since the publication of the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016), the source of information for this description.
Japanese stilt grass rapidly spreads to form extensive mats that displace native plant species that are unable to compete. It can alter natural habitats by changing soil chemistry and creating low light conditions that shade out other species.
Information for this species profile comes from the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016).