mulching iwth paper – Extension Master Gardener Volunteers of Durham County

By Susan Sharp, NC State Extension Master Gardener^SMvolunteer 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

Article Short Link https://wp.me/p2nIr1-6ou

By Eric Wiebe, NC State Extension Master Gardener^SM volunteer of Durham County

(Image credit: Allie Mullin)

As the gardening season is winding down, it’s time to start thinking about your fall and winter tasks. Near the top of that list should be thinking about mulching your plantings. A tour of your yard will probably reveal thin or bare spots where last year’s mulch has either broken down or been washed or blown away (those darn leaf blowers!). You may also want to put a winter cover on areas where you had vegetables growing. Finally, you may also have new areas you are preparing as garden beds where mulch will need to go around the new plantings.

Why Mulch Matters

First, let’s review why you want to be mulching in the first place. The primary reason most people mulch is for a combination of weed suppression and moisture retention. However, there are other just as important reasons to mulch. If you are using organic materials, you have the important benefit of in-place composting and humus generation, improving the biodiversity of the ground ecosystem throughout the mulch and into the surrounding soil and plants. Depending on type and placement, mulch can also help with erosion control and compaction. In addition to absorbing and holding moisture from rainfall, it can also minimize water splash from the underlying soil onto plants–potentially limiting the spread of harmful soil-borne fungi, such as blight. Finally, there may be good aesthetic reasons to mulch to create sharp delineations in color and texture in the landscape.

Types of Mulching Materials

What kinds of materials can you mulch with? Broadly speaking, mulches are grouped into organic and non-organic types. Included in organic materials are natural products, primarily from trees, that have been processed but will readily decompose–this includes cardboard, newspaper, and other paper products.

Inorganic Mulch

The most common non-organic materials are landscape fabrics made from plastic–either sheet or woven–and various types of stone. These are often used together, as the landscape fabric can be placed under the stone to help suppress weeds and keep the stone from migrating into the soil. Plastic sheet, with or without perforations, is also used in fruit and vegetable production, often applied with specialized machinery. The rest of the blog post will focus on the more popular and beneficial organic mulches used by home gardeners.

Organic Mulch

While shredded hardwood comes to mind when thinking about mulch, other organic materials like leaves are great sources for mulching material. As they decompose, leaves improve soil health by providing nutrients and improving both water retention and percolation. (Left) Newly-raked leaves ready to be spread across the garden. (Right) Leaf mulch after a year of decomposing. (Image credit: Eric Wiebe)

Organic materials can be found from a variety of sources. The best and most convenient materials are those found right in your yard. This includes leaves, new or partially decomposed; grass clippings, compost, and plant and tree trimmings. There is the argument to be made that the best mulch sources are the most local, as they represent the local ecosystem and can best support the macro-/microbiome already in your yard.

(Left to right) Arborist chip drop ready to be spread and a close-up of this type of mulching material. (Image credit: Eric Wiebe)

If you don’t have enough organic sources of mulch within your own yard, consider arborist wood chips. These are the product of local tree services as they cut down and chip tree limbs and can be acquired for free through a national service, ChipDrop (https://getchipdrop.com/). This product is still relatively local, representing tree species from your area and, for most of the year, contains a mixture of bark, wood, and leaves.

Research has shown that wood chips perform well with regards to moisture retention, temperature moderation, and weed control. While you can buy shredded (often from grinding whole trees), bark, and sawdust mulches from garden centers, many of these products are imported from other areas, bagged in plastic, or dyed. All of these factors both increase your cost and reduce their sustainability. In contrast, the biochemical and physical diversity of arborist chips resists compaction and creates a more diverse habitat for insects and microorganisms. Over time, the bark, wood chips and leaf matter will decompose, adding nutrients to the soil.

Paper products like newspaper and cardboard have long been used for sheet mulching/lasagne gardening techniques. Here a homeowner is using cardboard shipping boxes stripped of labels and tape as a base layer to be covered by other natural mulching materials. (Image credit: Melinda Heigel)

There are many, many other types of organic mulches that can be used. Pine straw is popular in NC and can be very local if you have a lot of pine trees on your property. While compost can also be used as mulch, its cost typically prohibits its use over a large area. Finally, paper products in the form of cardboard, newspaper, and brown paper have long been used as a form of sheet mulching. Note that you typically have to cover these materials with a somewhat dense mulch (e.g., partially decomposed leaves) in order to hold it in place. While there has been some social media controversy over the use of cardboard, it is still generally believed to be a quality mulch material when applied properly. Note that you should carefully remove non-decomposable elements such as tape and staples, and avoid glossy, non-brown cardboard as they may contain unwanted inks and plastics. While grass clippings can be used as a mulch, it tends to decompose quickly, not drain well when wet or blow away when dry. They may also contain excessive fertilizer or herbicides. Instead, consider mulching it in place in the lawn.

Tips for Effective Mulching

There are best practices to consider when using any mulch, and some considerations for specific types of mulches. First, to the best of your ability, plan how much area you have to cover and what volume of mulch you need. As a rule of thumb, you will need 6 cubic yards of mulch to cover 1,000 sq ft at 2″ deep–you generally will want to keep your mulch 1-3″ thick. However, this thickness will be driven in part by the density of the mulch; how well it retains moisture and allows oxygen to pass through it. Lighter mulch material such as pine straw or newly raked up leaves can often be deeper, while wood chips should be around 2-3.” If mulch is piled too deep, is too fine, or retains too much water, air cannot penetrate the mulch layer and the mulch and underlying soil can be depleted of oxygen. Mulch decomposing in low oxygen (anaerobic) conditions will sour, or ferment, producing methanol and acetic acid, which can be toxic to plants.

(Left to right) A properly-mulched tree has a few inches of mulch that extend to the edge of the drip line (or area that mirrors the tree’s crown). The root flare is visible at the base of the tree, as mulch isn’t in direct contact with the trunk. By contrast, the tree on the right is an example of all-to-familiar over mulching. Known as “volcano mulching,” mounding mulch around the trunk is harmful to your tree, leading to its decline and possible death. (Image credit: Penn State Extension; Eric Wiebe)

For all plants and trees, make sure to apply mulch all the way out to the drip line as you want to provide weed suppression, moisture retention, and soil benefits to all of the roots of the plant. Trees are another case of the dangers of over or improper mulching. Mulch should not come in contact with the bark of the tree as it promotes the kind of dark, moist environments that allow harmful fungi to enter the tree through the bark. Think donuts rather than volcanoes when you mulch your trees.

Impact of Mulch on Soil Chemistry

Using pine straw mulch as an acidifier on blueberries. (Image credit: Eric Wiebe)

Mulches can influence soil chemistry. While most of the time, this is happening in a good way, you need to understand the properties of the mulch you are using. Pine straw and pine bark, for example, has a naturally low pH. While this may be a problem on some plants, you can use it to your advantage with acid-loving plants such as azaleas or blueberries. Organic mulches with a high carbon-to-nitrogen ratio, like sawdust, hardwood bark, or wheat straw, may induce a short-term nitrogen deficiency as it breaks down. If plants in the mulched area become chlorotic and growth slows, consider applying one to two pounds of nitrogen per 1,000 sq ft to compensate. Almost all mulches will have a very localized nitrogen deficiency at the boundary between the soil and mulch. However, this is good as it inhibits weed growth.

Many of the basics and a few of the nuances about mulching have been covered here. As with most aspects of gardening, you can, if you want, continue to go down the rabbit hole of the science of mulching. The resources below will get you started!

Resources and Additional Information

General guidelines on mulching trees and shrubs: https://extension.umd.edu/resource/mulching-trees-and-shrubs/

Mulching garden beds:

https://carteret.ces.ncsu.edu/2021/08/mulching-your-garden-beds

https://yardandgarden.extension.iastate.edu/how-to/using-mulch-garden

Benefits of using arborist wood chips: https://pubs.extension.wsu.edu/using-arborist-wood-chips-as-a-landscape-mulch-home-garden-series

Tips for mulching in the spring: https://ext.vt.edu/lawngarden/turfandgardentips/tips/Springtime_mulch.html

Comprehensive guide to mulching materials: https://extension.unh.edu/sites/default/files/migrated_unmanaged_files/Resource007193_Rep10385.pdf

Sheet mulching/lasagne gardening gardening with paper products: https://extension.oregonstate.edu/gardening/soil-compost/sheet-mulching-aka-lasagna-composting-builds-soil-saves-time

https://extensiongardener.ces.ncsu.edu/2020/01/sheet-mulching-2020-winter-piedmont-news/

Problems with over mulching: https://pender.ces.ncsu.edu/2020/10/can-too-much-mulch-killl-plants/

Article Short Link: https://wp.me/p2nIr1-5iR