Category: Japanese stiltgrass

Managing Japanese Stiltgrass in NC

On By durhammastergardenersIn Gardening information, invasive plants, Invasive species, Japanese stiltgrass, mulching iwth paper, Uncategorized, weed

By Susan Sharp, NC State Extension Master GardenerSM  volunteer of Durham County

Many NC gardeners know both the joys and the frustrations of managing landscape beds and woodland areas in the summer.  If we’ve done the planting and maintenance (and if a drought hasn’t done too much damage), plants like black-eyed Susan (Rudbeckia hirta), hyssop (Agastache), sage (Salvia), and Stokes’ asters (Stokesia laevis) are providing color and pollinator interest. On the edges, however, invasive summer weeds will be creeping in.  Some will have grown slowly since spring seeding, while others have volatile spreading habits. Here we look at one of the most challenging: Japanese stiltgrass (Microstegium vimineum).

Close-up view of Japanese stiltgrass (Microstegium vimineum) amongst other green foliage.

Late summer appearance of Japanese stiltgrass before flowering – optimum time to control. (Image credit: Andrea Lane CC BY-NC 4.0)

Japanese Stiltgrass – History and Current Status

There are reasons why one of the most popular Horticulture Information Leaflets on the NC State Extension publications website is the one entitled Japanese Stiltgrass Identification and Management. Japanese stiltgrass (Microstegium vimineum), also known as Napalese browntop or bamboograss, is a summer annual in the grass family (Poaceae) that invades both disturbed and undisturbed areas in woodland and landscape settings. Researchers first reported it in the US (Tennessee) around 1919, likely introduced as packing material for fragile items from Asian countries. It now invades at least 26 US states and multiple countries globally, and the NC Invasive Plant Council classifies it as Rank 1 – Severe Threat in NC.

A dense patch of Japanese stiltgrass (Microstegium vimineum) growing in a shaded woodland area, surrounded by trees and underbrush.

Japanese stiltgrass overgrowth in woodland setting (Image credit: Susan Sharp)

Identification and Growth Habit

Japanese stiltgrass germinates in early spring. Key vegetative identification characteristics include rolled vernation and a short membranous ligule1. Additionally, the leaf blades are short and broader than most grasses, around 3 inches long and ½ inch across, often with a distinctive silvery stripe of reflective hairs along the midrib. As the season progresses, the stems grow increasingly wiry, turning color from light green to reddish purple through the summer.

Close-up of Japanese stiltgrass (_Microstegium vimineum_) stem with leaf blades with silver midrib, reddish stem and young flower spike against a light background.

Japanese stiltgrass flower in September (Image credit: Susan Sharp)

The flowers are racemes with branched spikes appearing from late August to September, but they often hide within the leaf sheaths. Seeds then easily spread by multiple means carried by awns2, including wind, water, people and animals, making pre-flowering control a top priority. Plants will wilt to a light tan shade after frost, but some persist throughout the winter, especially in wooded landscapes.

Four samples of grass awns displayed in varying orientations against a blue background, with a scale bar indicating 1 cm.

Japanese stiltgrass awns for seed dispersal (Image credit: Steve Hurst. Provided by ARS Systematic Botany and Mycology Laboratory)

The plant prefers partially shady, moist areas but adapts readily to other conditions and most soil types. It spreads during the growing season by stolons, and each plant can disperse over 1,000 seeds that remain viable for up to four years. Gardeners now find it in woodlands, shaded to partial-sun landscapes, and low-maintenance turf throughout the southeastern US, including Durham County. Unfortunately, it provides little to no food value to animals or insect herbivores, so natural controls on its spread are minimal. If left unchecked, stiltgrass spread can overtake native landscapes in three to five years.

Stiltgrass Control and Management

Controlling Japanese stiltgrass requires persistence and good timing. Mulch is generally ineffective, but denial of light early in the season using blockers like thick cardboard can help in landscape beds. We have experimented with this approach in a home landscape bed this season and have seen less infestation. Hand pulling can help in beds – perfect for meditative weeding, but hard on the gardener’s back. For larger infestations, mowing prior to seeding can reduce spread effectively, and flame weeding works in moist sites when fire hazard is low.

A landscaped area showing a mixture of dried grass and fallen leaves along a pathway, with dense green vegetation in the background.

Roadside Japanese stiltgrass mowed in late August (Image credit: Susan Sharp)

Importantly, timing is crucial: gardeners should complete all manual/mowing control measures by mid to late August, before the flowers become visible, to prevent seed production. If removed or mowed before August, the remains can be left as mulch in woodland or shaded areas. Bag all plant debris for disposal if it’s later in summer near the flowering season.

For chemical control, herbicides that target crabgrass will generally control Japanese stiltgrass as well, both pre-emergent and post-emergent. The NC State Horticulture Information Leaflet publication provides details on proper use and timing. The NC Agricultural Chemicals Manual offers additional product-specific guidance. As always, consulting the herbicide label for usage guidance is essential.

Notes

1– In grassy plants, the ligule is a thin outgrowth found on the inner surface of a leaf where the leaf blade meets the sheath that wraps around the stem. It acts as a protective barrier against pests and other stressors for younger leaf tissue. A membraneous ligule is a thin, translucent outgrowth at the junction of the leaf blade and sheath.

2–An awn is a small, usually bristled or barbed projection often used by grassy plants to boost seed dispersal.

Resources and Additional Information

NC State Extension Plant Toolbox: Microstegium vimineum (Japanese Stiltgrass) | North Carolina Extension Gardener Plant Toolbox

NC Invasive Plant Council on Japanese stiltgrass: Invasive Species

USDA PLANTS Database: USDA Plants Database Plant Profile General

NC State Extension Horticulture Information Leaflet: Japanese Stiltgrass Identification and Management | NC State Extension Publications

2026 North Carolina Agricultural Chemicals Manual: 2026 North Carolina Agricultural Chemicals Manual | NC State Extension Publications

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From Beloved to Invasive: How does it happen?

On By durhammastergardenersIn benign non-native plant, bird friendly habitat, bugleweed, conservation, crape myrtle, Durham NC, ecological sustanability, ecology, gardening, Gardening information, gardening NC, heavenly bamboo, hellebore, how plants become invasive, Invasive Atlas of the United States, invasive plants, Japanese stiltgrass, lenten rose, lesser threat invasive plant list, liriope, monkey grass, nandina, native ecology, native ecologynative plant ecology, native plants, Natives, NC biodiversity, NC conservation, NC Native Plants, New Hope Bird Alliance, non-native plants, ox-eye daisy, perennials, polyculture, privet, protecting native plants, Rose of Sharon, Russian olive shrub, sustainable garden design, sustainable gardening, sustanability, Uncategorized, urban garden, urban gardening, watch list for invasive plants

By Jeannie Arnts , North Carolina Extension Master GardenerSM volunteer of Durham County

I have volunteered as a recorder for the New Hope Bird Alliance (formerly Audubon) Bird Friendly Habitat (BFH) team since 2018. The BFH team, consisting of a plant expert and a recorder, visits homeowners’ yards to identify native and invasive plants and make recommendations for improvements to achieve an ecologically beneficial habitat for birds, insects, and other wildlife. Since I have joined the group, plants previously recognized as non-native, non-invasive plants have been moved onto the “Watch List” or “Lesser Threat Invasive” list. Other plants previously considered lower threat have been moved to a higher threat category. The question arises, “What is it that changes a benign non-native into an invasive?

When is a Plant Determined to be Invasive?

Plants are categorized as invasive once they disrupt the ecology of intact, functioning eco-systems, leading to loss of biodiversity and habitat degradation. This results in huge economic damage valued in the billions of dollars to agriculture, forestry, and personal property. Invasive plants compete with our natives for critical and often limited resources like sunlight, water, nutrients, soil, and space. Anyone who has ridden the train at the Museum of Life and Science in Durham and seen the Russian olive shrubs (Elaeagnus sp) overtaking the landscape along the tracks or been on a hiking trail in many Triangle forests and seen the stiltgrass (Microstegium vimineum) engulfing the entire ground cover of the forest floor can easily see the impact of invasive species.

Russian olive shrubs (left) out-compete native plants and dominate riparian areas primarily in central and western USA. Japanese stiltgrass (right) was accidentally introduced into Tennessee around 1919 as a result of being used as packing material for porcelain from China.  it has invaded many woodlands in North Carolina. (Image credit: NC State Cooperative Extension)

What Factors Influence a Plant to Become Invasive?

Biologists have been “vexed for decades” by the question of what causes some plants, once thought to be benign, non-invasive exotics, to become a risk to our eco-systems due to their invasive characteristics. The ecologist, Charles Elton, wrote the book, The Ecology of Invasions by Plants and Animals, in 1958 and, more than 100 years earlier, Charles Darwin pondered this question during his voyage on the Beagle (1831-1836). Johnny Randall, former Director of Conservation Programs at the NC Botanical Garden, noted that one reason plants become invasive is that in their new environment, they no longer have natural controls, such as pests, pathogens, and herbivores. This gives them an advantage over native plants that have been part of a region’s ecology for millennia; consequently, the invasives often out compete the natives.1

In addition, a plant’s propensity to become invasive is a function of the plant’s own biology, including a relatively short generational period, large seed production, its ability to reproduce asexually (without the need for fertilization), and having large fleshy fruits, such as those produced by Autumn or Russian olive trees (Elaeagnus sp), privet (Ligustrum sp.) and heavenly bamboo (Nandina sp.) With this latter trait, birds will eat the berries and deposit the seeds far from the original location of the plant.

A non-native, is especially prone to invasion when it sets its roots in a “matched habitat” similar from which it came, i.e., their native ranges tend to have similar temperature extremes, precipitation levels, and seasonal cycles. Stiltgrass (Microstegium vimineum) is an example of a plant that meets most of the criteria for becoming invasive. It is an annual that produces up to 1000 seeds per year, has no natural controls, reproduces asexually, and its seeds are distributed by the wind. In addition, the seed bank may take up to five years to germinate. Many gardeners who think they have eliminated stiltgrass on their property one year are befuddled to find a number of plants from the seed bank sprouting the next summer. The good news is that if you continue to manage the stiltgrass, you will have fewer plants each year.

Beloved Plants that Become Invasive

I think we can all agree that we want stiltgrass eliminated from our property, but there are non-native plants that have been beloved by gardeners for generations that are being added to the invasive lists, much to the consternation of gardeners. One example is the lenten rose (Helleborus orientalis).

Some hellebores  have started to escape into woodland areas and are able to stifle our favorite native understory flowers. They prevent seedlings of other plants from getting established as dense mats of their offspring grow. (Image credit: NC Extension Toolbox, Bob Gutowski CC-BY-NC-SA-2.0; Jim Robbins CC-BY-NC-4.0).

There are many good reasons that hellebores are such a beloved plant: they bloom over the winter months when very few other plants are blooming; they require little care; they are deer and rabbit resistant; they tolerate a wide range of light conditions; including light shade; and they survive even deep frosts. Unfortunately, they meet many of the conditions that place them at risk to become invasive in our region: they have no natural pests or pathogens; they can successfully fertilize themselves (although bees will seek nectar and pollen from the plants); and they produce a multitude of fertile seeds. While there is not a perfect native substitute for hellebores, the gardener may consider planting a matrix of sedges (Carex species), coral bells (Heuchera americana), and ferns, many of which are host plants, to provide winter interest .

While not yet on the invasive lists in N.C, another beloved plant that is of concern is the crape myrtle (Lagerstroemai indica). Its spread is being tracked in Southern states by the Invasive Atlas of the United States and the plant’s spread is being watched with caution by conservationists in N.C. Each flower of the crape myrtle produces a prodigious number of seeds that are carried or blown far from the mother plant. I have had a crape myrtle in my yard for probably the past 40 years and it has only been recently that I have seen it sprouting up elsewhere in my yard and ¼ acre woods.


Crape myrtles are seen along roadways and in gardens in North Carolina but conservationists have raised concerns because it outcompetes many native plants (Image credit: NC Plant Toolbox, skdavidson)

Liriope (Liriope muscari and L. spicata), bugleweed (Ajuga reptens), Rose of Sharon (Hibiscus syriacus), and ox-eye daisy (Leucanthemum vulgare) are all common ornamental plants that have been added to the NC Invasive Plant list as “Low Threat” species. While they have the potential to harm our local ecology, they are not yet doing so.

Liriope (Liriope muscari), bugleweed (Ajuga reptens), Rose of Sharon (Hibiscus syriacus), and ox-eye daisy (Leucanthemum vulgare) are plants that many of us have in our garden. They are considered to be “Low Threat” to native plants of North Carolina. (Image credit: North Carolina Toobox, Manuel-CC-BY-2.0; Jim Robbins-CC-BY-NC-ND; Frank Mayfield, CC-BY-SA-2.0)

As gardeners, we can control the spread of potentially invasive plants in our own yards or we can choose to remove them and plant a native that supports our native ecology. A follow-up blog will suggest options to consider for replacing invasive plants with natives that power our ecosystems.

Notes

  1. Personal communications Peter Schubert, NC Invasive Plant Council, October, 2024 and Johnny Randall, former Director of Conservation Programs, NC Botanical Garden, October 2024.

Resources and Additional Information

NC Invasive Plants List adopted by NC-IPC, November 16, 2023NC Invasive Plant Council
https://nc-ipc.weebly.com/uploads/6/8/4/6/6846349/invasive_plant_list_-_ranked_-_2023-11-16.pdf

Grzędzicka, E., Assessment of Habitat Selection by Invasive Plants and Conditions with the Best Performance of Invasiveness Traits, February, 2023. https://www.mdpi.com/1424-2818/15/3/333

Invasive plant Atlas of the United States University of Georgia-Center for Invasive Species and Ecological Health, October 2018 https://www.invasiveplantatlas.org/index.cfm

Jones, M., Gaster, R. Invasive Species, NC Cooperative Extension, Lee County, July 30, 2019 https://lee.ces.ncsu.edu/2019/07/invasive-species/

Moony, H.A., Cleland, E.E., The Evolutionary Impact of Invasive Species, Proceedings of the National Academy of Sciences. May 2001, 98(10) 5446-5451 https://www.pnas.org/doi/full/10.1073/pnas.091093398

Moorman, C, Megalos, M, Douglas, K. Invasive Plants and Your Forests, NCSU Extension Publication. Revised September 11, 2024. https://content.ces.ncsu.edu/invasive-plants-and-your-forests

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