Japanese Stiltgrass: Accurate Identification

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- Invasive Japanese stiltgrass is an aggressive invader of woodlands and threatens forest ecosystems.

Infestations can reduce native plant diversity, degrade wildlife habitats, and disrupt important ecosystem functions.

This video will examine the identification characteristics of Japanese stiltgrass.

Positively identifying stiltgrass is necessary before beginning any management activities.

Japanese stiltgrass was initially documented in 1919 in Tennessee.

It is now found across most of the Eastern United States as far West as Texas.

Stiltgrass is an annual grass that germinates in the spring and dies back each fall.

It is a prolific cedar with a sprawling growth habit.

It is often found growing along trails and roads where it easily spreads to the forest understory.

The tiny seeds are carried on shoes, cars, ATVs, and logging and road maintenance equipment.

Once introduced, it is extremely difficult to eradicate from a site.

The grass stems form a dense tangled mat usually one to three feet in height, but can grow up to six feet in length.

Taller plants typically lie flat along the ground or overlay other vegetation.

The leaves are elongate and lance-shaped, longer than they are wide with smooth edges.

Each leaf blade is between one and three inches in length.

On the upper surface, a silvery slightly off-center stripe of reflective hairs runs the length of each leaf.

Stiltgrass stems are thin, delicate, and wiry.

They often have multiple stems branching near the base.

Each stem is supported by small stilt-like prop roots which give the species its name.

Longer stems tend to sprawl sending out rootlets known as stilt roots from the nodes along the lower sections of the stem.

The leaves and stems turn a purple brown color in fall as the plant dies back.

The stems remain over winter forming a dense matted layer or thatch.

The winter thatch is tan to orange in color.

The flower spikes emerge in late summer or early fall.

The spikes are one to two inches in length.

Stiltgrass may have one, two, or three spikes.

Stiltgrass spreads exclusively by seed with each plant producing up to 1,000 seeds annually.

The seed is small and highly mobile arriving in new areas accidentally in contaminated soil clinging to shoes, vehicles, and heavy equipment.

The seeds float and are easily dispersed in roadsides, ditches, streams, and wetlands by water movement.

They can remain viable in the soil for up to five years and germinate when conditions become suitable.

Stiltgrass has one notable lookalike, native whitegrass.

Whitegrass is very similar in growth habit and site preferences, but has two distinct differences from Japanese stiltgrass.

The flower spike on whitegrass is much larger, up to 10 inches long, and its stem has patches of dense white hairs around the base of each leaf.

It is also a perennial grass so it does not die back each fall.

Another trait of Japanese stiltgrass that helps to differentiate it from most native grasses is its smooth leaves.

In contrast, native grasses typically have a rough textured leaf blade.

The invasive Japanese stiltgrass is considered one of the most damaging invasive plants in the United States.

Train yourself how to correctly identify this invader and distinguish it from native lookalikes before applying any control measures.