Wavyleaf basketgrass (Oplismenus undulatifolius)

Synonyms: Oplismenus hirtellus ssp. undulatifolius

Common Names: Basketgrass, wavy grass

Description:

Wavyleaf basketgrass (Oplismenus undulatifolius) is a low, shade-loving grass native to parts of Europe and Asia, first found in North America in 1996 at a Maryland state park [1][2]. It spreads fast across shaded forest floors, forming dense carpets that smother native plants and block young trees from growing [1][3]. MISIN tracks it as a serious forest invader to catch and report early ? and its sticky, seed-bearing bristles cling to shoes, pets, and animals, which is exactly how it hops to new woods [1][3].

Habit:

Wavyleaf basketgrass is a low, creeping perennial grass of shady woods, only about 8 to 12 inches (20 to 30 cm) tall, with stems that trail along the ground beneath the leaf litter and root as they go [1][3]. Its name gives away the best identifying feature: the short, dark-green, sharply pointed leaf blades have distinct ripples or waves running across the width of the blade, like a washboard [1][3]. The leaf sheaths and stems are noticeably hairy [3].

The easiest time to confirm it is fall. It flowers from mid-September into November, later than most grasses, and stays green late into the season, so it stands out on a forest floor after other plants fade [3]. At flowering it produces spikelets with long, sticky bristles (awns) that cling to anything brushing past [3].

At-a-glance cues:

1. Short, dark-green leaf blades with rippled waves running across the blade [1][3]
2. Low, creeping stems that trail over the ground and root at the joints, with hairy stems and leaf sheaths [1][3]
3. Forms dense carpets over the shaded forest floor [1][3]
4. Flowers in fall (mid-September to November) with long, sticky, clinging bristles on the seed heads [3]

Leaves:

1. Shape: ovate to lance-shaped, elongated, sharply pointed, dark green [1][3]
2. Size: about 0.5 to 1 inch (1.5 to 2.5 cm) wide and 1.5 to 4 inches (4 to 10 cm) long [1]
3. Surface: distinct ripples or waves running across the width of the blade ? the key feature [1][3]

Stems:

1. Habit: low and creeping (stoloniferous), trailing beneath the leaf litter and rooting and branching at the joints; runners can grow several feet long [1][3]
2. Size: slender, about 1 to 3 mm across [3]
3. Surface: covered in scattered hairs (1 to 2 mm long); the leaf sheaths are hairy too [3]

Flowers:

1. Form: small grass spikelets bearing long awns (bristles) that secrete a sticky substance [3]
2. Arrangement: in a slender flowering stalk held above the low foliage [3]
3. Bloom time: mid-September to November ? later than most grasses [3]

Fruit and seeds:

1. Type: grass seed enclosed in a spikelet tipped with long, sticky awns [3]
2. Dispersal: the sticky awns cling to animals, pets, shoes, and clothing, carrying seed long distances ? the main way it reaches new woods [1][3]
3. Output: dense stands can produce upward of 1,000 seeds per square meter each year [3]

Habitat:

Wavyleaf basketgrass is native to parts of Europe and Asia and is not native to North America [1]. It is a plant of the shaded forest floor ? full-canopy hardwood forests, forest margins, and shady stream sides ? and it is unusually tolerant of deep shade, letting it invade closed-canopy woods that many weeds cannot [3].

Since its first North American record in Maryland in 1996, it has spread through Mid-Atlantic forests, and it grows in temperate coastal-plain, piedmont, and mountain woods [1][3].

Reproduction:

Wavyleaf basketgrass spreads two ways, and the first is the one a homeowner or hiker is most likely to move without realizing it. Its fall seed heads carry long, sticky awns that cling to fur, shoes, socks, and clothing, so people, pets, deer, and other animals carry the seed from an infested woodlot to a clean one [1][3]. A dense stand can make over 1,000 seeds per square meter in a year [3].

It also creeps outward on the spot: its trailing stems root as they go and can run several feet, knitting a solid mat across the ground [1][3]. Because so much seed builds up, the seed can keep sprouting for years after the visible plants are gone, so a cleared site needs watching over several seasons [1]. For control, the timing that matters is to remove plants before the sticky seed heads form in early fall.

Impact and Damage:

Wavyleaf basketgrass is not toxic and is not a health hazard to people or pets. Its harm is to forests.

It forms a dense, continuous carpet across the shaded forest floor, and that mat crowds out native wildflowers and other ground-layer plants and blocks the seedlings of native hardwood trees from taking root and growing [1][3]. The result is a loss of plant diversity in the forest understory and, over time, a threat to how the forest itself renews [3]. Its tolerance of deep shade makes this worse ? it can move into intact, closed-canopy woods, not just disturbed edges [3].

This is one of the more serious emerging forest invaders in the region, which is why early detection matters so much. A small patch caught before its sticky seeds spread is far easier to stop than a carpet that has already seeded the surrounding woods [1][3].

Similar species:

Japanese stiltgrass (Microstegium vimineum) is the plant most often confused with wavyleaf basketgrass ? both are low, sprawling grasses that carpet shady forest floors. The difference is in the leaf: Japanese stiltgrass has a flat blade with a shiny, silvery line of hairs running slightly off-center down the middle, and it is an annual that dies back each year, while wavyleaf basketgrass has the distinctive rippled, wavy blade, hairy stems, and is a perennial that stays green later into fall [1][3]. Both are invasive and reportable, so a photo-backed report is the safest response to either.

Monitoring and rapid response:

Signs to watch for:

1. A low, creeping grass carpeting the shaded forest floor, with short dark-green leaves that have ripples running across the blade [1][3]
2. Hairy stems and leaf sheaths; runners rooting at the joints beneath the leaf litter [1][3]
3. Fall-blooming seed heads (mid-September to November) with long, sticky bristles that cling to clothing and fur [3]

What you can do:

1. Hand-pull it ? the shallow, creeping stems come up easily, and pulling is considered more effective than other methods for small patches [1]. Pull before the sticky seed heads form in early fall so you do not scatter seed while you work [1][3].
2. Remove the whole mat, including rooted runners, and bag all plant material for the trash ? do not compost it near the woods [1].
3. Clean your boots, tools, clothing, and pets before leaving an infested area ? the sticky seeds are the main way this grass travels, so brushing them off on site keeps you from carrying it home or to new woods [1][3].
4. Because seed can keep sprouting for years, check and re-treat the site for several seasons after the visible plants are gone [1].
5. For a natural area crew: map and prioritize small, outlying patches before they seed, work outward from clean areas, coordinate boot-and-gear cleaning at the site, and plan repeat visits across several years for the seed bank.

When to call a professional:

1. Large or well-established carpets, or infestations spread across a forest where hand-pulling cannot keep up
2. Any low forest grass you cannot confidently identify ? it is easily confused with Japanese stiltgrass, so a photo-backed report is worth more than a guess
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Penn State Extension. Wavyleaf Basketgrass. extension.psu.edu
2. Global Biodiversity Information Facility. Oplismenus undulatifolius (Ard.) P.Beauv. gbif.org
3. Wisconsin Department of Natural Resources. Wavy Leaf Basket Grass (Oplismenus undulatifolius). dnr.wisconsin.gov

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