Groundcovers, do they need to be green all the time?

As I think about the landscapes that I have idealized from an early age, they are green and full of life all year long.  But I grew up in an area that did not have four seasons and at a time when droughts and water management were not something that we worried about.  So the expectation of having some sort of green ground cover 365 days a year was not difficult to achieve.  Now after living in the Northern half of the US for 40 some years I have come to realize that having four seasons means that there is a good chunk of time when the plants in the landscape take a break and rest. 

Vinca minor is a widely used and invasive groundcover, originally from
central and southern Europe, that is often used where an evergreen carpet is desired.   

English ivy forms a dense evergreen cover that spreads by both
 runners and seeds.  It is particularly damaging when it is allowed to climb trees.

This brings up a question, does all the ground need to be covered all the time?  Yes, for protection from erosion, extreme temperature fluctuations and evaporation coverage is beneficial.  Groundcovers, both living and dead, also provide wildlife habitat.  There has been increasing awareness of the importance of  providing habitat for overwintering insects as they are critical sources of food for birds and other predators.

Alleghany spurge, Pachysandra procumbens, native to the mountains
of the Southeast, acts as a more naturalistic groundcover.

Does it need to be green all the time? No, not really.  But there is a desire among many for a lush green ground covering year around.  This desire is' might I say, for primarily aesthetic reasons.  To get this year-round green in temperate climates many folks are drawn to non-native species like Japanese pachysandra, English ivy, Vinca minor , yellow archangel (Lamiastrum galeobdolon), wintercreeper euonymus, mondo grass and lilyturf.  Most of these species are invasive in many parts of North America.

Here's my listing of the importance of having a ground cover, roughly in order of importance:

Minimize Erosion by holding soil against the forces of rain and wind;
Water management, by improving water infiltration and reducing evaporation;
Soil Health, by avoiding compaction, maintaining good aeration, moderation temperature and moisture extremes.  All these help maintain a healthy soil microbiota;
Maintain ecology by providing places for native insects to overwinter, less disturbance provides better survival rates for overwintering insects and nesting sites;
Weed management, its harder for seeds to geminate on shaded soil, in competition with established plants or where roots cannot take hold; and,
Aesthetics, create a visually pleasing composition.

As I alluded to above, the ground cover does not need to be green and growing year round.  In fact, depending on the climate and the environment the most appropriate ground cover may not be green at all.

In the majority of cases the material covering the ground will be some sort of plant material.  Having a actively growing root network under the soil to stabilize it and keep it biologically active is the ultimate goal. Where climate and conditions allow having a living mulch is an ideal solution for protecting the ground. The plants making up this living mulch need not be green though all four seasons.  They just need to continue to to hold the soil in place.  Green and actively growing on top is nice but not a year-round necessity.

The following are descriptions of how natural groundcovers function in three habitats that are similar to what you might encounter in a residential setting: Woodlands, Grasslands, and Deserts.

Mayapples, Podophyllum peltatum, provide a dense cover throughout
the spring as the forest canopy leafs out.  They hold the soil
with a wide spreading network of rhizomes.

Spring beauties are another spring ephemeral that are found on forest edges.

Woodlands: In Eastern deciduous forests the ground is covered year around by a layer of decomposing fallen leaves, natural compost.  Similarly, in coniferous forest there is a slowly decomposing layer of fallen needles.   Depending on the amount of light there is an understory of perennials and shrubs adapted to those conditions.  Where there are gaps in the canopy and accessible soil, new plants can get a start.  Depending on the composition of the seed bank these may be native or non-native species.  In a well balanced system the amount of undergrowth will be determined by the available resources.  Because of the way the available light changes through the year the nature of the ground cover plants also changes through the seasons.  In springtime the ground may be covered with ephemeral species like mayapples and Dutchman's breeches.  By summer these disappear and the ground plane is less densely covered with shade tolerant species like ferns and sedges and understory trees and shrubs.  Fall and winter feature the return of fall leaves which slowly decompose to replenish the soil with nutrients as well as serve as habitat for overwintering creatures.

Grasslands: In grasslands the winter ground cover consists of dead leaves and stalks from the past growing season and a network of crowns of the overwintering plants.  A healthy layer of this plant debris serves to protect the soil and fill the necessary roles of a ground cover.  The root networks of perennial grasses and forbs help to hold the soil.  Standing stalks of tall grasses and perennials form important habitat for some overwintering birds and insects.  Where the ground has been cleared by natural (fire) or unnatural (cutting and raking) processes, space is opened up for new plants to grow, both desirable and unwanted, depending on the seeds that are present.

Little bluestem, Schizachyrium scoparium, is a common
component of many eastern grasslands and dry meadows. 
Even after it dies back in winter it maintains its visual appeal.

Arid lands: In desert environments growth is limited by the availability of resources, particularly water.  Here you typically see plants growing much further apart because they are limited by the amount of available moisture. Root systems of perennial species tend to be much larger in order to access sufficient moisture for growth and survival.  Particularly in hot deserts most of the organic material that falls to the ground gets burned up and does not contribute to build organic material in the soil for the long term.  In these environments a natural ground cover would be inorganic in nature, rocks, stone and sand. While plants may not stabilize the soil on the surface, many have very wide spreading shallow roots systems adapted to harvest rainfall before it evaporates.   These wide systems can help to stabilize the soil, leading to less erosion.  Trying to maintain a green ground cover in a desert environment can be very resource demanding and not at all sustainable.

The ocotillo and purple-tinged prickly pear cactus each have shallow
wide-spreading roots to scavenge water thus limiting what else can grow nearby.

If green in winter is really what you need there are several native species here in the Mid-Atlantic that fit the bill.  Native (near)evergreens include, wintergreen (Gaultheria procumbens), green and gold (Chrysogonum virginianum), heuchera, tiarella, Alleghany spurge (Pachysandra procumbens), golden groundsel (Packera aurea), evergreen ferns (Christmas and intermediate wood ferns) and some sedges, like creeping sedge (Carex laxiculmis) are good for partly shaded locations.  For sunnier sites moss phlox (Phlox subulata), wild strawberry (Fragaria virginiana), common and creeping junipers, barren strawberry (Geum ternatum), as well as some grass-like plants like prickly bog sedge (Carex howei).  On most sites these plants will still be green through most of the winter, but they generally will not be lush with fresh foliage

Golden groundsel in winter.  The interconnected leaf rosettes
are held close to the soil.

In spring golden groundsel puts on fresh growth and sends up flowers.  

Why Lawn

Lawn maintenance consumes an incredible amount of time and money.  But what is the purpose of a lawn, and could those resources be put to better use?

Let’s first start with the question:  Why have a lawn?  There are some practical reasons.  Recreation - lawns are often used as open and safe places for children, and some adults, to play.  Protection - having open sightlines around your dwelling, with few hiding spaces can make one feel safer.   Buffer space - keeping nature at a ‘safe’ distance.  This could be to control insects or wildlife, or, in fire prone areas, an open, healthy, lawn can protect a dwelling from fire. Status - a perfect lawn is often equated with ones class.  Going back a century or so, if you had the resources to expend on maintaining a perfect lawn then one must be pretty well off.  

A pretty common sight: large lawns on multiacre lots.  

In his 1841 treatise on landscape gardening, A. J. Downing advocated for the need of having a proper lawn to have a tasteful and civilized property.  He translated the Romantic style of late 18^th-century English landscape architects into a form more suited to the United States, particularly in the Hudson Valley and Mid-Atlantic.   Downing was extremely influential in setting the course for American landscape design into the 20^th century.  Another key event in making the lawn a standard feature was around 1870 when the reel lawnmower, which had been invented in England, came to the US.  This made keeping a mown lawn more practical. 

Achieving the ‘perfect’ weed-free lawn was made much easier with the development and marketing of the herbicide 2,4 D (1944) for residential use.  A lawn treated with this was made free of nearly all non-grass (dicot) plants.  This meant that most flowering plants which could support pollinators (e.g. clover, fleabanes and heal-all) could be eliminated from lawns.  The result was a nearly flawless (one could say featureless) green carpet of only grass-like (monocot) plants.     

Considering the history of landscape design from earliest times, there seems to be a need for humans to exert control over nature, despite the costs.  People, in general, feel much more comfortable in a landscape that is readable or understandable.  These are places where they can see the ins and outs and how to move through the space.  Think of the composition of a photograph or painting.  There are elements that draw the eye through the piece to a focal point.  Crisp or well defined edges are also important in creating readability.  I’ll admit that I do feel a sense of satisfaction when I look back on an evenly mown and edged green carpet. 

Let’s look at some data about lawns in the United States:

Acreage of lawns   Looking on the internet I found figures of between 40 and 50 million acres of residential turf grass in the US.  Compare that to the total amount of land used to grow corn which averaged at about 90 million acres between 2018-2022 (USDA data).  These figures are based on satellite imagery.  Most corn is grown without irrigation.  If you compare the irrigated acreage for corn of about 12 million acres to that for turf, then you come up with 3-4 times as much lawn as irrigated corn. 

Amount of gas used   Based on EPA figures from 2005, 800 million gallons of gasoline were used to power lawn care equipment each year.  Using this weeks’ national average of $3.72/gal you are talking about $3 billion dollars annually.  On top of that, lawn mowers and other small-engine powered lawn equipment, which have no pollution control devices, are significant contributors to air pollution.  Estimates are that combined landscape care equipment contributes about 5% of the total air pollution, CO, hydrocarbons and NOx .

Amount of water used on residential landscapes   EPA estimates of water use for landscape purposes is 9 billion gals/day (WaterSense 2013).  Most of that is treated potable water that could be used for domestic consumption rather than poured onto the ground.  With the increasing severity of droughts, particularly in areas of the Southwest where population is shifting towards, there are very real problems with providing all the water that is needed. 

So considering that lawns and lawn care have increasing costs and negative effects it is time to ask why and how much lawn can we afford and what are the alternatives.

Trends away from lawns:

No mow May.  Started in England as a push to provide early season pollinators with flowers that are common in English lawns.  Blindly adhering to a no-mow-May program in a country with so many diverse climates and types of lawns as the US is often inappropriate.  To be useful, the lawn or property in question needs to have a population of plants with early blooming flowers that the pollinator population likes.   Depending on the climate the appropriate time for suspending mowing could be as early as February or into the later part of May.  If you have a monoculture of Kentucky blue grass there is little benefit to pollinators in skipping a month of mowing, there is just nothing of benefit there for them.  If you have a diverse ‘lawn’ containing native weeds like violets, self-heal (Prunella vulgaris), fleabanes (Erigeron sp.), spring beauties (Claytonia virginica) and the like, then allowing those to come into bloom would have a positive effect.  If you really need to mow, take the effort to mow around the blooming plants until they are done.  Lawns can also be interplanted with spring bulbs.  While not native, very early bulbs like Crocus, Chionodoxa and Scilla can add interest to an early spring lawn.  These bulbs have usually completed their growth and blooming cycle by the time the need for mowing kicks in.

I have been allowing this patch of Philadelphia fleabane
to develop without mowing.  It reaches peak bloom
in mid-May.  I usually mow it down in early June
after it sets some seed. When not in bloom plants survive
as low-growing rosettes.  

While there is the oft repeated advice to never cut more than one third of the length of the grass blade at a time, I rarely let that force me to cut the lawn before I’m ready.  I can’t say that I have ever noticed a problem by occasionally letting the lawn get too long between cuts.  In those cases when I do the biggest problem is the long clippings left on top.  A mulching mower can help deal with that.  All these problems are magnified on the ‘perfect’ lawn, where any imperfection becomes blaringly obvious.  In a diverse, multispecies lawn imperfections blend into the mosaic of plant colors and textures.

Lose the Lawn  This is a phase that is used by many people when voicing their concern about the amount of resources being pouring into and onto lawns.  You can get excellent advise on this subject for university extension services.  Doing an internet search on ‘lose the lawn’ and your state of region can give you information on lawn alternatives suitable for your area.  For example try this link to the UMD extension for the Mid-Atlantic region.

Climate appropriate landscaping   This is another phrase used when talking about more sustainable landscape practices.  Simply put, it is using plants that grow well with the resources that are naturally available.  Native species appropriate to the local climate require much less water and other inputs than turf or other non-adapted species.  When there are no plants suitable, look to using other materials to achieve the design goals.  It also means avoiding the use of plants and materials that require an extraordinary amount of inputs to maintain them.  

As droughts are becoming more frequent and severe, many municipalities are instituting water restrictions and/or offering enticements for installing water efficient landscaping.

What can one do?

>If you have a lawn, mow and water when lawn needs it, rather than on a preset schedule.  This can be difficult with lawn services since making a flexible schedule with multiple clients can be very difficult.  I did see on the web some services that offer options for having a less frequent mowing schedule.  That may be a move in the right direction.  In general lawns maintained at 3-4" have deeper roots making them less dependent on frequent watering.  Also the taller turf shades the soil which reduces weed seed germination and evaporation or soil moisture.

>Replace high maintenance lawn grasses with climate appropriate turf.  The US is divided into 3 zones for turf grass, cool season, warm season and the transitional zone between them.  A nice overview of turf grass types for the various regions of the United States can be found in this blog post from Landscape America.  While most turf grasses are not native to North America a few are.  Buffalo grass (Bouteloua dactyloides) is a native species found in the plains from Southern Canada to Northern Mexico.  It has been developed as a drought tolerant turf grass.  A native of the Gulf States, St. Augustine grass (Stenotaphrum secundatum) has been cultivated and planted along the east and west coastal areas of the US.  Fine fescues are well adapted to the Pacific Northwest and Northeastern states.  A few subspecies of red fescue (Festuca rubra) are native to North America; however, the blends suited for turf usage contain a variety of fine fescues most of which are not native.  There are at least three blends of these fine fescues that have been selected for use in cool season growing zones that are drought tolerant, need little fertilization.  Look for Eco-Lawn, Eco-grass or No Mow fine fescue blends. 

This patch of lawn is mostly fine fescues that is mown about every two weeks. 
It looks like regular 'grass'.  If I did not mow it it would would develop a
 fine silky, mounded texture that fine fescues are noted for.  

>Develop a tolerance for having mowable green, rather than a perfect cloned lawn.  My lawn, in the Mid-Atlantic region, is a mixture of tall and fine fescues, nimblewill (Muhlenbergia schreberi, a local native species), probably some purple top (Tridens flavus, also native), violets, fleabanes, clover and some less desirable (but tolerable) weedy stuff.  A diverse lawn requires fewer inputs to maintain.

>Consider alternative ground covers.  Regionally native species are preferred because, in addition to requiring little to no mowing, they also support local wildlife.  Some lower growing North American natives that can replace, or be incorporated into a lawn include frog fruit (Phyla sp.); pussy toes (Antennaria sp., for sunny dry conditions), and golden ragwort (Packera aurea, partly sunny, moist conditions).  Moss is perfect for a shady spots. Again, doing a search on ‘lose the lawn’ coupled with your region yields results that offer a list of alternative ground covers.  I recommend focusing on web sites managed by university extension services as providing the most unbiased results.

This patch of golden ragwort bursts into bloom in April. 
It is semi-evergreen and grows to about 6" tall.  It is slowly expanding,
but can be kept under control with mowing.

>Reduce or eliminate fertilization.  In many situations it is a vicious cycle.  Fertilizer is needed to replace the nutrients removed when grass clippings are removed while mowing.  Then, the more fertilizer you add, the more the lawn grows, then the more there is to mow.  By leaving grass clippings in the first place and mowing in the leaves in the fall, you are recycling the nutrients in place and feeding the microbes living in the soil.  Using a mulching mower will reduce the amount of clippings visible on the lawn.

>Reduce area committed to lawn and replace with bedding, meadow-type plantings, successional plantings, or cropping (hay fields).  When reshaping the lawn, go for simple shapes that can be mown efficiently, avoid tight turns and acute angles.  I have one triangular area that requires a lot of backtracking to mow.  A rectangle or oval could be done with less backtracking. 
A successional planting builds on the natural process of succession.  Succession is the natural process where the mix of plants on a site changes over time, and it begins when one stops mowing.  East of the Mississippi River, the sequence is usually bare land becomes grasslands, which in turn becomes shrublands which eventually turns into forests.  This process usually takes many years.  The land owner could  speed up the process by planting desirable shrubs and trees to create an idealized version of the natural landscape.  Intervention by the landowner can also pause succession at various stages such as as a meadow or shrubland.

Here is a possibility of allowing some succession of  local native species
(redbuds, dogwoods, asters, etc.).  Clean edges and sightlines to and
from the dwelling confer intention to the landscape.  This more
diverse landscape offers much more to the local ecology. 

>When creating a new space, clean edges, whether straight or curved, convey a sense of intention in the landscape.  A wilder space surrounded by a clean edge is visually more comforting than a totally wild area.

>Where climate is not suitable for growing plants, use hardscape or inorganic mulches. Hardscape does not have to be impermeable concrete.  Dry laid stones and pavers allow for water infiltration which reduces runoff problems.

>Be creative with the space, put in artwork to fill the space and send a message.  On a recent trip to Sebastapol, CA we visited Florence Ave where many of the residents have sculptures in the front yards by local artist Patrick Amiot. 

This owl sculpture is complemented by a variety of
perennials in this lawn-free front yard.

The minimal landscaping around this catfishing dog works quite well. 
The colors of the spiky New Zealand flax play well with the colors in the statue.

Reducing the area committed to lawn does not have be be done all at once.  It can be done one area at a time, or by expanding planted beds or wilder areas a little bit each year.  I would love to hear about your experiences with reducing resources committed to maintain a lawn.

Pull! Pull! Pull!

 Yes Pull!  Now is the time to pull out Japanese stiltgrass, Microstegium vimineum.  This invasive species is rampant in the eastern U.S. from Georgia to Massachusetts and west to the Mississippi River.  It affects home landscapes and natural area alike.  Here in the Mid-Atlantic region the grass is putting on a growth spurt prior to going into bloom.  So the plant is expending a lot energy now to grow taller and produce flowers.  It also means that it is a lot easier to pull out without getting on you knees.  Since this grass in an annual, keeping it from going to seed can go along way to controlling its spread and reducing its numbers.  

Early in the growing season Japanese stiltgrass stays relatively low, rooting at several nodes along the stem.  In late July it starts growing upward to gets its flowers higher off the ground.  If it were only that simple.  Stiltgrass not only produces flowers at the top of the stem it also has flowers at most of the vertical leaf nodes buried within the stems.  These are referred to as cleistogamous flowers.  

  This image shows flowers at the top and at the
lowest nodes. Cleistogamous flowers can occur all
along the stem as well.  Roots can also form roots at each
node where they contact the ground. If the grass is not
cut early in the season most of the flowers are
concentrated toward the top of the stem.

These cleistogamous flowers are one of the reasons stiltgrass is so hard to eliminate.  If you cut or mow stiltgrass early in the season without removing it completely, these stem flowers will form even lower on the plant requiring even more careful pulling later on.  I've seen a recommendation to leave the stiltgrass grow until late summer so that most of the flowers are higher in the plant.  Then when you pull you are able to get most all of the flowers with the least effort.  (Sounds good to me.)

Here are some highlights of my nearly 10-year battle with stiltgrass here in Maryland:

Pre-emergent herbicides are very effective in existing lawns and smooth surfaces.  These chemicals interfere with the development of germinating seeds but do not have a strong effect on established plants.  These must be applied in early spring prior to the germination of the stiltgrass seeds.   I have been using a preemergent containing Dimension (dithiopyr) for several years.  I took two years of successive treatments to get nearly complete removal of stiltgrass from the lawn in treated areas.  Moss has not been effected. 

Late summer pulling of previously uncut stiltgrass, especially in shady areas, has reduced the amount of stiltgrass in subsequent years.  This does require a multiyear effort.  Since nasty things like poison ivy, multiflora rose and wineberry can hide in the tall stiltgrass, it is important to wear gloves and arm protection when pulling.

Here's the before photo.  I wonder why there is so much
stiltgrass just in this area, and why so close to the path. 
It could be from the lawn mower blowing seed from
 the other side of the path where there is a lot more stiltgrass

After about 30 minutes of labor you can see the
existing plants reappear. (Some of the freshly
pulled stiltgrass is piled in the foreground-left.)

Weed-whacking and raking of the cut grass before it begins to bloom is very effective, BUT you need to get really close to the ground to remove all the stiltgrass. Raking up the cut grass helps existing plants bounce back. 

Identify and plant native species that can compete with stiltgrass. Two exceptional plants that seem to outcompete stiltgrass are golden ragwort (Packera aurea), and mayapple (Podophyllum peltatum).  Other plants that are strong competitors include clearweed ( Pilea pumila) and grasses that grow well in shade: river oats (Chasmantheum latifolium), mannagrass (Glycera sp.), Virginia wildrye (Elymus virginicus), and  nimblewill (Muhlenbergia schreberi).  Also there are a number of sedges that will persist under cover of stiltgrass and can form a dense cover if given the chance.  Rosy sedge (Carex rosea) is one example that does quite well on my property.  I recently noticed that there was much less stiltgrass growing in an area where celandine poppy (Stylophorum diphyllum) and mannagrass have been spreading.  The exclusion of stiltgrass is not as great as with Packera, but it is noticeable.

This opening under the trees is free of both garlic mustard and stiltgrass now. 
In early spring it is fully covered with mayapples and a few woodland phlox.

The area just beyond the bench has benefited from annual late
summer pulling and by a dense crop of mannagrass that totally
shaded the area from late April to early June.  The stiltgrass that is
growing there now is only a few inches tall.  Compare that
to the 2 foot tall stiltgrass in the foreground-left.

It's not just pulling in late summer and fall.  There are things you can do earlier in the year to control stiltgrass.  Here is a table summarizing some removal strategies:

Japanese Stiltgrass Control

Season	Actions	Pros	Cons	Comments
Late Winter Early Spring	Pre-emergent treatment	Effective in lawns and smoother (even) surfaces with access to soil surface.  Allows lawns and perennials to get a head start.	Will affect all germinating seeds for several months.  Uneven coverage on rough surfaces.  Application needs to be at the right time (same time as for crabgrass).	Takes at least 2 years to knock down seed bank to see significant progress.  More time to complete elimination, if ever. Many pre-emergents for crabgrass control are also approved for Japanese stiltgrass (aka Mary's grass, on the label)
Late spring-Summer	Herbicide	Grass selective herbicide leaves broad leaf plants and some sedges intact. Try products containing Fluazifop-p-butyl	Difficult to control collateral damage, especially with non-selective herbicides	Targeted application and use of selective materials may limit side effects.
Late spring-Summer	Pulling	Non-toxic and selective.  Opens space for other species.	Labor intensive; left over stilt grass will expand to fill gaps.	If removal is not complete this will need to be repeated at the end of summer
Late summer/Early fall	Cutting/ pulling/ burning	All methods to reduce the amount of seed	Need to complete actions before seed begins to ripen.	Copious amounts of seed being produced, need to be thorough and avoid spreading any ripened seed.

You can read more information about my on-going battle with Japanese stiltgrass in previous blog-posts by entering 'Microstegium' in the 'Search this Blog' box at the top of this page.

Good luck and I would like to hear about your experiences battling this invasive species.

Living Mulch

Mulching garden beds has been a consistent ‘must-do’ for many gardeners.  Mulching reduces moisture evaporation, suppresses weeds, adds nutrients to the soil, reduces erosion and in many cases improves moisture absorption. Wood and bark chips are the most common materials employed.  Recently I have seen and read more about the negative effects of wood chip mulches. In particular when these mulches are over applied and allowed to compact, they can actually retard rain water absorption.  Thickly applied mulch can retard the growth and expansion perennials.   In his book The Know Maintenance Perennial Garden, Roy Diblik discusses how unnatural wood chip mulch is.  In areas that get adequate rainfall to support a tight matrix of plants, a living, or green, mulch is the ideal.

For many sustainable and naturalistic gardens the goal is to create this ‘green mulch’ or ‘living mulch’ by filling the space between garden features or larger plants with more plants.  ‘Green mulch’ is living plant material that performs all the functions of wood mulch such as weed suppression and soil moisture and temperature moderation.  In addition properly selected green mulches offer additional benefits like supporting wildlife and insects with food and cover, lower maintenance (since they do not to be replenished or broken up on a regular basis).  This green mulch may be a single species or a variety of plants that form an interlocking matrix. This matrix is most like what you would encounter in a meadow or woodland setting.

An example of a classically mulched bed. 
Each plant is distinctly identifiable and  there are no
random plants to confuse the composition.

One problem with green mulches is that they can look weedy due to lack of readability, no clear design or cluttered appearance.  Many folks are more comfortable with a landscape or garden where the features are clear and recognizable.  Having beds with clean edges is a quick way to make a garden more legible.  This human desire for legibility is also seen in the preference of many for plants neatly separated by oceans of mulch. 

One means of creating a green mulch is to install plants closer together so that they quickly grow together to create a continuous green carpet of foliage. This is one of the themes of the book New Naturalism, by Kelly Norris, published in 2021.  The trick here is to create plant communities that a good match to your site conditions and that the plants play well together. 

An example of a green mulch.  Creeping phlox, Phlox subulata,
and wild strawberry, Fragaria virginiana, have grown together
 to form a 4-6" deep ground cover.  Shrubs and perennials,
like the wild geranium, Geranium maculatum, here,
 are able to grow through.

Another route to a green mulch is to plant lower grow species as a matrix between your feature plants.  The trick here is to keep your garden readable so that the matrix does not obscure your design intent.  By way of example consider what bindweed does to a garden.  While it grows quickly to fill all the voids in the garden it also grows up and over taller plants resulting in tangle of plant material that has no discernible form, no starting or ending points and little textural contrast. (Kudzu does this on a much larger scale, draping a woodland edge with green vines, effectively removing all contrast between the trees.)  Consider instead a perennial bed where the spaces between plants are filled with low growing violets.  The glossy round leaves of the violets don’t interfere with the forms and textures of taller perennials or shrubs.  A list of some of the lowest growing  Mid-Atlantic natives includes:  Pussytoes (Antennaria sp.), wild ginger (Asarum canadense), Green and Gold (Chrysogonum virginianum), wild strawberry (Fragaria virginiana), barren strawberry (Geum fragarioides), Meehan’s mint (Meehania cordata), partridgeberry (Mitchella repens), golden ragwort (Packera aurea), various species of phlox (Phlox divaracata, stolonifera or subulata),  foamflower (Tiarella cordifolia), common violet (Viola soriana),  and  short sedges like rosy and ivory sedge (Carex rosea  and  C. eburnea ).

Golden ragwort is excellent native ground cover.  It spreads rapidly
 in moist, partly sunny locations.  It also seems to suppress invasive
 weeds like Japanese stilt grass and garlic mustard.

 

Using spring ephemerals for this purpose is a very natural means of creating a matrix.  These perennials naturally flourish early in the year when tree and shrub canopies are open, then slowly go dormant as the canopy closes up.  They return again the following spring.  In the Mid-Atlantic you may find Dutchman’s breeches and squirrel corn (Dicentra sp.), mayapple (Podophyllum peltatum)  and Virginia bluebells (Mertensia virginiana)  as common examples of these.  A limitation with using ephemerals is that they do totally disappear after setting seed.  They are ideal in an established perennial or shrub bed where you just need something in early spring while the larger plants are leafing out.  

Ephemerals, like cutleaf toothwort, Cardamine concatenata (in bloom),
 and Dutchman's breeches, Dicentra cucullaria, fill out in early spring.
but disappear as the tree canopy fills in. 

Using short-lived species that survive primarily by reseeding is another means to establishing a sustainable living mulch.  By nature these are opportunistic gap fillers.  As the longer lived perennial and shrub layers get established these reseeders tend to be squeezed out as their preferred, open habitat disappears.  Yellow fumewort (Corydalis flavula), American pennyroyal (Hedeoma pulegiodes), common yellow woodsorrel (Oxalis stricta), and self-heal ( Prunella vulgaris) are some of the shorter species that can be used in this way.  Taller, showier species that can be used as temporary gap fillers include wild columbine (Aquilegia canadensis), Partridge pea  (Chamaecrista fasciculata), fleabanes (Erigeron annuus and E. philadelphicus), and black-eyed Susans (Rudbeckia hirta).

Wild columbine, growing about 2' high, is relatively
 short lived in gardens due to competition and rich soils.
It produces a lot of seed so that it can reappear in other suitable
 locations where seeds can make soil contact and
have access to sunlight. (unmulched areas).

Yellow wood sorrel is considered a weed in many cases.  However,
 this native plant satisfies the requirements of a living mulch quite well. 
It grows quickly and produces lots of seed to fill gaps, is relatively short lived,
and is easily displaced by larger plants. As a native it also supports wildlife,
 particularly bees and birds.  Its lax, floppy habit detracts from it appearance,
making it appropriate around much larger plants and shrubs
or where this flop is not a distraction.

Oxalis stricta is very similar to its European relative, O. europea. 
Each has the same common name, common yellow woodsorrel. 
The North American species can be distinguished by the horizontal
disposition of the seed stalks (indicated by arrow). 
O. europea has seed pods on ascending stalks.

So if you are willing to give up the repetitive chore of mulching your garden beds, consider having your plants do that job for you and establish a living mulch.

It's Stiltgrass Time Again

As summer is peaking so is the time to focus on removing Japanese stiltgrass, Microstegium vimineum.  At this time (beginning of August) in the Mid-Atlantic region this invasive grass is putting on a growth spurt, but has not yet begun to develop viable flowers. In one of my previous blog posts on this subject I prepared this table to help keep track what to do to combat stiltgrass at each point in the season.

Season	Actions	Pros	Cons	Comments
Late Winter Early Spring	Pre-emergent treatment	Effective in lawns and smoother (even) surfaces with access to soil surface.  Allows lawns and perennials to get a head start.	Will affect all germinating seeds for several months.  Uneven coverage on rough surfaces.  Application needs to be at the right time.	Takes at least 2 years to knock down seed bank to see significant progress.  More time to complete elimination, if ever.
Late spring-Summer	Herbicide	Grass selective herbicide leaves broad leaf plants and some sedges intact. Try products containing Fluazifop-p-butyl	Difficult to control collateral damage, especially with non-selective herbicides	Targeted application and use of selective materials may limit side effects.
Late spring-Summer	Pulling	Non-toxic and selective.  Opens space for other species.	Labor intensive; left over stilt grass will expand to fill gaps.	If removal is not complete this will need to be repeated at the end of summer
Late summer/Early fall	Cutting/ pulling/ burning	All methods to reduce the amount of seed	Need to complete actions before seed begins to ripen.	Copious amounts of seed being produced, need to be thorough and avoid spreading any ripened seed.

While it is too late to count on herbicides cutting close to the ground level and pulling at very effective methods to employ at this time in order to prevent Japanese stiltgrass from reproducing.  Because this is an annual grass, keeping it from reseeding goes a long way to eliminating from your environment.  In wooded areas and existing beds where there are many desirable plants intermixed with the stiltgrass I opt for pulling as my preferred approach.  Since it has grown fairly tall by this time, I usually pull it by the handfuls then leave it out in the sun to dry.  If you are weed whacking it you could leave the cut grass in place to dry; however, I’ve read that doing this can generate a thick layer of thatch that can be difficult for other plants to grow through.  Whenever possible I will rake out the cut grass and leave it in the sun.  If I’m confident that there is no viable seed in the stiltgrass I will mow over the dried grass to help return that organic material to the soil.

For several years I have been removing stiltgrass manually from this
shady mossy lawn.  This year I treated it with a preemergent herbicide
 in late April and am seeing only a few instances of stiltgrass.  In addition
to the moss and some fine fescue and sedges there are patches of selfheal,
Virginia jumpseed and white avens. 

I’ve noticed that this year that the stiltgrass is more brittle and harder to pull cleanly out of the ground.  This may be due to the drier weather that I am experiencing at this time.  I’m afraid that I may be leaving more rooted fragments that may be able to regenerate.  I will try to time my next pulling campaign to be after a significant rainfall to soften the soil. 

Another thing I’ve noticed this year is that the plants that I am pulling up have multiple rooting points along the stem.  I’m thinking that as I am reducing the number of stiltgrass plants, year by year, there is more room for them to spread laterally.  So a partial success, but it means that there is still more work to be done.

I've treated this woodland path for two consecutive years with a
preemergent as indicated by the white line.  You can see the
bright green stiltgrass to the back and on the right. In the treated area
are a variety of grasses and sedges.  Deer tongue grass is the
largest species here.  In late March this area is covered with spring beauties.

Looking over my property I see that the most significant reduction in Japanese stiltgrass is where I have applied a preemergent herbicide in early spring.  This year I applied Dimension™ (dithiopyr) at the higher recommended rate.  This is expected to be effective for 3-4 months.  It was applied at the time recommended for crabgrass control (380 GDD(32°F)), or about the time when the forsythia were coming into full bloom.  I am seeing next to no stiltgrass in many parts of the lawn as well as in the treated parts of my ‘mown meadows’.  Better results are seen where I have treated for at least two consecutive years.  In these meadows and in the more natural areas I try to avoid treating the same area with a preemergent two years in a row.  This is to allow the seeds of the many desirable plants to germinate on the off-years. 

As far as native plants that compete well against Japanese stiltgrass, golden ragwort, Packera aurea, seems to actually suppress the growth of stiltgrass.  Virginia wild oats, Elymus virginicus, and bottlebrush grass, E. hystrix,  compete well.  What I believe to be fowl manna grass, Glyceria striata, has been able to out compete Japanese stiltgrass in shady moist areas.  This grass develops early in the year with tall, thick growth that shades the ground.  The downside of this grass is that it dies back to the ground after going to seed in late June.  

This photo, taken at the end of May, shows thick growth of
a grass that I believe to be fowl manna grass.  The area inside
the white circle has been free of stiltgrass for the past two years.

 I have been posting blogs about my battle with Japanese stiltgrass since 2014, probably 3-4 times a year.  Following are links to several of the more informative posts.  Getting Ready for Stiltgrass 2021, July 2020 What to do about Stiltgrass Now, The Forsythia are in bloom, Now is the Time, and Making a Plan to manage Japanese Stiltgrass.