Stiltgrass Reaches Michigan

During four weeks of touring with our latin/jazz group Lunar Octet in California and Michigan this summer, this "jazz naturalist" kept encountering different variations on the problem of invasive species. In the Bay area of California, highly combustible introduced grasses dominate hillsides, threatening homes. A side trip to Cleveland took me close to where beech leaf disease was first identified 12 years ago. 

And then, housesitting for my friend Sam in Ann Arbor--our home base for various Michigan gigs--I was astonished to find Japanese stiltgrass growing in his garden. Now, the only thing that would be astonishing about stiltgrass in a New Jersey garden would be its absence. Stiltgrass has become nearly ubiquitous in Princeton--coating roadsides, establishing broad monocultural meadows in our woodlands, smothering our gardens with its stilt-like growth. An annual that spreads rapidly for lack of any wildlife that find it palatable, it dies back in the fall, leaving a frozen ocean of brown in the forest, and billions of seeds to sprout the next spring. 

Stiltgrass is Not Yet Everywhere

That ubiquity makes it hard to believe that there are still many parts of the U.S. where stiltgrass has yet to spread. Until recently, though, Michigan was one of them. For a New Jersey gardener, traveling to Ann Arbor used to be like stepping thirty years back in time to a stiltgrass-free landscape. 

My fantasy, upon discovering this uber-invasive in Sam's yard, was that I had through uncanny serendipity happened upon the first colony of the plant in the area, and at a time of year when it could be pulled before it went to seed. What finer gift could a housesitter give to a homeowner and his neighbors than to nip an invasion of stiltgrass in the bud? This jazz cat was going to put a botanical bully back in the bag. 

The Horse, the Cat, the Barn and the Bag

But no. The stiltgrass--which I'm guessing first arrived as a hitch-hiker in topsoil or a nursery plant, or perhaps in the soil of a well-intended gift plant dug from some well-meaning friend's garden--had already spread far down the hillside towards the Huron River. 

Turned out Sam already knew about stiltgrass. Ann Arborites are a plant-savvy bunch. Their city already had a Natural Lands Manager, Dave Borneman, long before I moved away in 1995. Princeton hired its first Open Space Manager in 2021. Most towns and cities don't even have one.

I contacted Dave, who now has his own habitat restoration business doing prescribed burns, to ask about the status of stiltgrass in Ann Arbor. He didn't say the cat was out of the bag, but he did say the horse had left the barn. "Sadly, the horse has left the barn on this species locally. We’re seeing it pop up fairly widely now in eastern Scio and western/northern AA."

The first occurrence of stiltgrass was in fact reported seven years ago, on Sept 1, 2017, in an announcement by the state Dept. of Natural Resources. A collaboration between the DNR and a nonprofit called The Stewardship Network sought to identify and knock out the initial population, said to have been limited to one property, but to no avail. 

The First Sighting in Wisconsin 

Wisconsin's situation sounds more hopeful, with only one known infestation that is allegedly being managed and kept to a limited area. A botanist visiting from Minnesota made the early identification. Somewhat less reassuring is a post by the Invasive Plant Association of Wisconsin (IPAW), that mentions my childhood landscape in the Lake Geneva area specifically as a place where people should be "on high alert" for stiltgrass. That would suggest its been reported there.

Is Stiltgrass Controllable?

It got me thinking about what can a town do about a new invasion? Once the cat has left the barn and the horse is out of the bag, is there anything to be done? Ann Arbor certainly needs no advice from afar. Its Wild Ones chapter has an excellent fact sheet on stiltgrass in Michigan, including a field guide with details to help with distinguishing stiltgrass from some similar-looking native grasses like whitegrass. Other groups like the Legacy Land Conservancy are also engaged, sounding the warning that Michigan gardeners and land stewards now face a challenge like no other.

“Stiltgrass is not like other invasives we have seen in Michigan, which spread relatively slowly and can be contained. Stiltgrass travels via water and deer, as easily as water itself."

But Princeton's experience with uber-invasives like stiltgrass and lesser celandine can be instructive. One can say these rapidly spreading nonnative species are ubiquitous, and yet there are locales--backyards, neighborhoods, upper valleys, hillsides--within the town where one or another invasive has yet to spread. In the preserves I have managed, I have had considerable success with proactive action to keep various areas free of the lesser celandine, garlic mustard, and porcelainberry that plague other areas of Princeton. 

Much can be done to slow the expansion of stiltgrass, by patrolling in late summer, particularly along the edges of trails. Even though stiltgrass has been in Princeton for many decades, it's still possible to walk through portions of preserves and see none, or to find just a few along the trail that can easily be plucked up before they go to seed in September.

One has to keep at it year after year, catch any invasion early, and be strategic in one's timing to maximize result and minimize effort. For larger patches that would be impossible to pull, late season mowing and/or application of very dilute herbicide prevents production of new seed. Doing this thoroughly and year after year ultimately exhausts the seedbank. Scroll down at this link for more information on these approaches. 

Patrolling for stiltgrass in a preserve can even be a good motivation to get out into areas you might not frequent otherwise, and do some botanizing. It's a chance to sharpen the eye, as one distinguishes between stiltgrass and the native whitegrass, and a few other plant species with similar appearance.

The top half of this photo is native perennial whitegrass. The bottom half is the invasive, annual stiltgrass. The latter is easy to pull. The former resists, because of its greater investment in roots.

In this list of lookalikes taken from the internet, the whitegrass and the northern shorthusk have been enjoyable for this plant geek to get to know a little better this year. As is typical of native species, they are fairly common in less historically altered preserves, but don't take over like stiltgrass tends to. 

Smartweeds (Polygonum spp.), with tiny, white to pink flowers on a short spike and a tell-tale dark blotch near the center of each leaf.
Whitegrass (Leersia virginica), which is well-rooted in the soil and has longer, thinner leaves than stiltgrass, with no mid-rib stripe.
Northern shorthusk (Brachyelytrum aristosum), with fine hairs on the top, bottom and edges of its leaves and stems, and leaf veins in a pattern resembling an irregular brick wall.

That's the upside of intervening in a situation where many feel frustration and helplessness. Intervention to stem the advance of hyper-aggressive plant species gets us outdoors, often prompting new discoveries and providing a chance to gain more familiarity with the native diversity we seek to protect.

Botanical Threats to Greenway Meadows--Neighbors Raise Concerns

Over the years I've sung the praises of Greenway Meadows, the park in western Princeton with an asphalt trail running down the middle of an expansive meadow. One post describes the beauty of broomsedge and cross country racers "testing inner nature in a natural setting." Another describes the exhilaration of riding a bike through the meadow on the way to an art exhibit opening at the Johnson Education Center.

More recent visits to Greenway Meadows have focused on the threats to the park posed by invasive species, and the need to act quickly, before the problem gets overwhelming. This past April, it was dramatic to see how lesser celandine is beginning to invade the meadow and the lawn.

Then this summer, Mimi Schwartz, who lives near Greenway Meadows, reached out about the park. She had noticed some attrition among trees along the Poetry Trail, and wondered if competition from the tangle of invasive shrubs growing beneath them might be a cause.

Another neighbor of the park, Jennifer Widner, is focusing on threats to the meadow--threats that surely go unnoticed by the many people who walk or jog down the asphalt trail, see a pleasing green, and look no closer.

Still apparent to all are the many native wildflowers in the field, among them common milkweed and wild bergamot. 

But on a visit to meet Jennifer, I was astonished to see the extent to which Sericea lespedeza (aka Chinese bushclover, Lespedeza cuneata) is beginning to dominate. This is an invasive species that has become a big problem in the southeast U.S. and the plains states, but was comfortingly rare in Princeton when I first moved here in 2003.

There are various species of native bushclover that can sometimes be found mingling with other wildflowers in a field, but Sericea lespedeza doesn't, as they say, "play well with others." It's behavior is more that of a bully.

In understanding the threat posed, it helps to have lived elsewhere in the country where Sericea lespedeza has had a longer track record of aggression. Living in Durham, North Carolina, near where the species was first introduced, in 1896, and is still widely used for erosion control despite many efforts to have it banned from seed mixes, I witnessed its capacity to displace native species. 

For those who say live and let live, and let it be, consider the ecological consequences if the meadow ultimately becomes a monoculture of an introduced plant with indigestible seeds and inedible foliage. Here's one fact sheet's description:

"Sericea contains a high concentration of tannic acid, which causes wild and domestic animals to avoid eating it, unless no other food is available. Animals then forage more intensely on native plants, which depletes the desirables and allows invasives to increase. Tannic acid leaches from sericea into surrounding soil, creating a toxic environment that prevents or slows the growth of other plants, giving it yet one more advantage."

Mimi and Jennifer have had some success engaging public officials on these threats, and the land managers at DR Greenway's headquarters nearby are potential allies. 

The project with the clearest solution is the freeing of trees from the invasive shrubs growing beneath. A greater challenge, requiring intervention and vigilance for years to come, will be stopping uber-invasives like lesser celandine and Sericea lespedeza. 

My experience, though, is that the work can get easier year to year, as steady effort makes the invasives less numerous. Down the road, or down the trail, as the threat recedes, those involved may get to experience that wonderful "walk in the park" feeling, where the botanical bullies have been sent packing, and require only a bit of ongoing vigilance and mild intervention to prevent their return.

For more information on Sericea lespedeza, try these: BlueRidge and Oklahoma State.

Related post:

Monocultures in the Making - 2013

Fuel Tank Raingarden Losing Out to Weeds

Maintenance is looked down upon and taken for granted in our culture. One reason for this is that, done well, maintenance is invisible. Our human tendency is to notice what is wrong, not what is kept right. At home, we are more likely to notice dirt and disarray than the cleanliness and order a housemate worked hard to achieve. 

In landscaping, the tendency is to fund and celebrate design and installation, then leave maintenance to the vicissitudes of chance, undertrained and undermotivated staff, and perennially strapped budgets. But even with the best designs, maintenance is what ultimately matters. Maintenance is destiny. 

Maintenance at its best is a form of love. In gardening, what we call maintenance is really more akin to the nurturance of parenting--an ongoing process of encouraging what is desired, and discouraging what is not. A garden can also be thought of as a playground. When maintenance is done right, plants that exhibit bullying behavior, like mugwort, don't get to play in the garden. 

Environmental groups encourage people to dig up some lawn and plant native wildflowers. These meadow plantings are characterized as low-maintenance, but that is true only if the weeds are caught early. Once the weeds get firmly established, maintenance becomes very difficult.

The only gardens I've seen flourish are those that are loved, like a child is loved. Love leads to knowledge and steady attention, and early intervention when things go wrong. 

Just off Witherspoon Street in Princeton there are contrasting examples of loved and unloved public gardens. 

The loved garden in this instance has almost no weeds--a standard few of us achieve. For years, near the entrance to the Community Pool, gardens around the Princeton Recreation Department offices were taken care of by "Vikki C. and Team PRD," as the sign proudly declares. That would be employee Vikki Caines. Vikki's glorious plantings expanded over the years well beyond the Rec. Dept. building. She retired in 2023, but when I asked her, she assured me that her gardens would continue to be well kept. 
 

By contrast, just down the street, past the Princeton First Aid and Rescue Squad, lies a rain garden that collects water from hard surfaces around the town's fuel storage tank. Regulations require that raingardens be dug and planted to collect and filter runoff from new paved areas. In a series of posts, I've tracked the destiny of this very public but largely unnoticed raingarden, whose extended limbo in 2020 ended with planting in 2021. But in gardening, as when a baby is born, the birth of a garden is not the end but rather just the beginning. In 2022, it was still full of color and easy to weed, but by 2023 the weeds were getting entrenched. 

I alerted town staff that the raingarden was losing out to the weeds, and was told that the municipality was weeding it once or twice a year, and was working "towards a system of regular maintenance, while balancing many, many other priorities."

This year, the original plantings are beginning to disappear beneath waves of mugwort, nutsedge, and other botanical bullies that don't play well with others--

weeds like foxtail grass, 

and wild lettuce--to name just a few of the species that maintenance crews would need to be able to recognize and remove. Note that the designer of a garden must know only the intended plants, while the maintainer, typically underpaid and underappreciated, must additionally know and recognize the many weeds that can invade.

This is the difference between loved and unloved gardens. Imagine a child being notified that a parent was "working towards a system of regular visits, while balancing many, many other priorities."

Now, a town's public works department does of course have many other priorities. Job one is to serve people, not gardens. But that being the case, the aim would be to keep the raingarden in the easy-to-maintain stage by catching the weeds early. Vigilance and early intervention--a form of love--save time. 

The only way Vikki Caines could maintain beautiful gardens while also doing her job in the recreation department was to stay on top of the weeding. 

Well-designed raingardens are easier than most gardens to maintain. The runoff they collect keeps the soil soft for easy weeding, and many native species of wildflowers and shrubs are adapted to flourish in the wet ground. Regulations can call for the digging and planting of raingardens, but the fate of the planting is left to chance. Weeds grow 24/7, while people are easily distracted. If the weeds take over, the ultimate response will be to mow it down and manage it as lawn. Nature's complexity, unloved, unnurtured, will once again be simplified and suppressed, the better to pursue other priorities.

Related posts: 

To Save a Raingarden, Know Your Weeds 

The Work Behind a Natural-Looking Meadow: Smoyer Park in Princeton

Maintenance Will Determine the Fate of the Betsey Stockton Garden

When I look at a plant, a garden, a meadow, a forest, I can see the future. It's a form of extrapolation, defined in the Oxford Dictionary as "the action of estimating or concluding something by assuming that existing trends will continue." I only realize now, writing this, that not everyone exercises such powers. Not everyone has been a gardener of landscapes for fifty some years, accumulating memories of myriad plant species and observing their behaviors. I've seen thriving raingardens and neglected ones, healthy meadows and forests, and degraded ones. I've observed how various invasive weeds spread and come to dominate, each in its own manner and at its own pace. These are the accumulated data points used to predict the future.

One very satisfying thing about extrapolation is that I can see, in my mind, the flower a bud will become. But with that same power to see a garden blooming while still in bud, I can look at a garden in what for others is glorious bloom and see the "seeds" of ruin--the scattered pockets of invasive mugwort, nutsedge, stiltgrass or lesser celandine, crown vetch or Chinese bushclover that without early intervention will quickly expand and ultimately prevail. 

My interventions--a broad mix of successes and failures--have taught me above all that early intervention can make the difference between hope and despair. 

One special garden in town that I stop by to check up on, like an old friend, is the Betsey Stockton Garden planted atop the Firestone Library at Princeton University. This is a complex native planting, containing 35 native grassland species. The person or crew maintaining the garden needs to be able to recognize and identify all 35 intended species, plus all the weeds that could potentially cause problems, not only when they're blooming but at all stages of development. 

That deep knowledge is a tall order. Knowing how little respect maintenance often gets, I worry about this meadow garden in the longterm. Will it receive the knowledgeable, strategic attention it needs to thrive? This photo of wild bergamot blooming with lots of clumping goldenrods suggests things are going well. 

Here, some black-eyed susans lend color, but the pink blooms of quickly spreading non-native crown vetch spell trouble.

New to me is a weed called rabbits foot clover, which may have hitchhiked in from whatever distant nursery the intended plants came from. This, too, was not caught early, and now poses a significant challenge.

Thankfully, there's only one small patch of the fearsome mugwort, but that could quickly expand if not dealt with quickly. Getting as close to zero tolerance for invasives as possible makes maintenance much easier. 

Maintenance is not given its due in part because success is often invisible. In a house, we note dirt's presence, not its absence. A well-run government agency doesn't make it into the news. The bass player who provides the harmonic foundation for a band often goes unnoticed until he plays a wrong note. In medicine, catching problems early doesn't pay as well as dramatically rescuing someone whose problem has grown into an emergency. Extrapolation can help with this. It allows us to see large consequence in small acts, to appreciate how big a problem has been avoided by digging up a small, isolated patch of mugwort.

I found a few relevant local writings. One was an opinion piece in the Daily Princetonian by an undergrad, calling for more native plantings on campus. Planting is a good start, but what goes unmentioned in the opinion piece is that maintenance determines any planting's fate. 

One strategy being used in newer native plantings on campus is to plant gardens with only three or four species, with lots of mulch inbetween plants. This reduces the amount of training required for maintenance. 

Other local writing specifically about the Betsey Stockton Garden can be found in the Princeton Magazine. It includes the list of intended plants (below), and describes the garden as low-maintenance, but that assumes the invasive weeds will be caught early and removed before they can spread.

The Betsey Stockton Garden was planted in 2018, two years after the demise of another campus native planting, around the Neuroscience Institute. Hopefully some lessons are being learned, and the University will bring the necessary expertise and strategic timing for maintenance to bear on this lovely, botanically complex planting. 

Native Plants Featured in the Betsey Stockton Garden
(Some are used on the High Line as well.)

Grasses: Carex comosa, Appalachian Sedge Carex pensylvanica, Pennsylvania Sedge Festuca ovina, Sheep’s Fescue Festuca rubra, Creeping Red Fescue Sporobolus heterolepis, Prarie Dropseed Elymus virginicus, Virginia Wild Rye Schizachyrium scoparium, Little Bluestem Tridens flavus, Purple Top Shade Plants: Aqueligia canadensis, Wild Columbine Aster laevis, Smooth Blue Aster Blephilia ciliata, Downy Wood Mint Erigeron puchellus, Robin’s Plantain Eurybia divaricata, White Wood Aster Polemonium reptans, Jacob’s Ladder Sisyrinchium angustifolium, Narrow Leafed Blue-Eyed Grass Solidago caesia, Blue-stem Goldenrod Solidago flexicaulis, Zig-Zag Goldenrod

Full-Sun Plants: Asclepias tuberosa, Butterfly Milkweed Aster laevis, Smooth Blue Aster Aster pilosus, Heath Aster Baptisia alba, White Wild Indigo Baptisia perfoliata, Catbells Centaurea cyanus, Cornflower Chamacaesta fasciculata, Partridge Pea Coreopsis lancelota, Lanceleaf CoreopsisEchinacea pallida, Pale Purple Coneflower Echinacea purpurea, Purple Coneflower Monarda fistulosa, Wild Bergamot Penstemon digitalis, Beard Tongue Rudbeckia hirta, Blackeyed Susan Solidago juncea, Early Goldenrod

Persistence Furthers With Garlic Mustard

Another weed that is risky to let get established in your yard is garlic mustard. The plant shoots up 1-3 feet high during its second year, and is easy to spot right now with its cluster of little white flowers.  The flowers look decent enough, but a laissez faire approach will lead to this weed taking over, altering soil chemistry and crowding out other flowers. The garlicky smelling leaves are edible, especially when young, but you'll never eat enough to control it. 

The strategy for combatting aggressive plants in the garden is different for each species. Garlic mustard is a biennial, meaning it gathers energy the first year, then blooms and dies the second year. If you leave it while it's flowering, chances are you'll forget to pull it later, after it has blended back into the green of the garden. By the time the plant dies and turns brown later in the summer, marring your garden with its skeletal remains, the seeds will have matured and dispersed, creating an even bigger problem next year. 

But foil its attempt to make and spread new seed, and the soil will eventually run out of seed to make new plants. Best to pull now, while in bloom, though it can be pulled any time before the seeds mature. "Grab low and pull slow" is a good motto for getting as much of the root as possible. Don't put the pulled plants in your compost pile. Even when pulled while young, there's still a chance that the flowers will mature into viable seed. 

To avoid having to stuff the pulled plants in trash bags to send to the landfill, what we've done at Herrontown Woods is pull every last one we can find, then pile them in an out of the way spot, so that any seeds that mature on the pulled plants and sprout the next year will be easy to find and pull. Pulling gets easier each year, until what once took hours now takes but a few minutes. 

All problems should yield so nicely to persistence. 

Related posts: 

• Girlscouts make quick work of garlic mustard at Herrontown Woods
• A Garlic Mustard Success Story from Michigan

Lawn Blotch 2024

Maybe people have another name for it, but every April there is a condition of some lawns that catches the eye. I call it "lawn blotch," which develops early in spring when the grass has yet to grow but other plants have.

Those other plants that spring forth here and there in a lawn might be Star of Bethlehem, which will later have pretty white flowers but spreads underground, popping up all over the place in your yard. 

Or they might be the pretty but terribly invasive lesser celandine,  which will become a nuisance for you, your neighbors, and your local nature preserve if you don't spray it or dig it up.

Or they could be a weedy allium that I call wild garlic. 

None of these plant species are native. Lesser celandine is poisonous. 

Lawn blotch has at least one positive, though. I've frequently seen the wild garlic being gratefully harvested by people of Asian heritage, to use in cooking like chives or onions. 

Lawn blotch as a phenomenon quickly passes, as the weather warms and the grass begins to grow, and lawn mowers once again impose a vertical conformity on the suburban landscape.

As an adendum, below is a fun quote from a post I wrote about lawn blotch eleven years ago. Though the climate has been changing considerably, lawn blotch still coincides with the Masters golf tournament: 

"As master golfers stride the perfectly groomed grounds of Augusta National this weekend, showing their mastery over a landscape that's kept in a perpetual state of arrested development, let us glance out the window for a moment at the less applauded realities of the suburban lawn. In the Masters tournament, only the hazards--the trees and shrubs--are allowed to reach maturity. For the golfer, any encounter with interesting plants is a sign of trouble. And in the yard, the main threat to calm conformity is the plant that seeks to lead a full life, by flowering and maturing its seed. (Full disclosure: I lettered in golf in high school, spent part of a summer mowing fairways, and probably developed a keen eye for plants while searching for lost balls in the nearby corn fields and the very rough rough of our neighborhood's rough-hewn golf course.)"

Lesser Celandine Spreading Into Local Parks

Poisonous to wildlife, crowding out other plants, be they native wildflowers or turfgrass, lesser celandine spreads across sunny lawns and shady forests alike, forming dense, exclusionary mats that can extend far into the distance. 

I've written many posts about this highly invasive plant, and how it can be controlled with targeted, minimalist use of herbicide if one catches it early in one's yard or in a local park or preserve. Invasions start with one isolated plant like this, which can be easily sprayed with systemic herbicide without damaging nearby vegetation. (Or dug up and thrown in the trash, not the compost.) Of course, one plant looks harmless enough, but its rapid spread will change your view from "Gee, that's pretty" to "Help!!"

Incredibly, this spring I happened upon a homeowner in our neighborhood who actively sells lesser celandine and other plants she digs from her garden, apparently via facebook marketplace. Her garden is infested with the plant, and so this noxious weed will hitchhike in the soil of any garden flower she sells. Though it has a pretty flower, it's rapid spread will cause gardeners to lose control of their gardens, and to then serve as vectors for the plant's additional spread to neighboring lands. I asked the woman about the ethics of selling and intentionally spreading such an invasive species, and she refused to even discuss it. She blamed her unreceptivity on someone who had confronted her about it in an unfriendly manner. I asked "What if a nice person were to raise the issue with you?" But she still refused any discussion.

I may be having more success with Princeton parks. This spring, a friend, Mimi, was concerned about the status of the London plane trees along the Scott and Hella McVay Poetry Trail in Greenway Meadows, and asked me to take a look. The trees definitely need some attention, given all the invasive shrubs growing beneath them, but I also noticed that lesser celandine is beginning to spread through the park's meadow and lawn. 

Here's that classic "first plant" which would ultimately carpet the whole meadow with its poisonous foliage if not treated. 

And here's an early infestation in the lawn that extends down to the ballfields and into the land surrounding the DR Greenway Johnson Center.

I urged the town to take action, and it appears they will. 

This spring has not been ideal for spraying lesser celandine. Days have remained cool, which I personally like, but it's best for the temperature to reach 50 degrees for effective treatment. Of course, having just written that, I come upon a source that says at least 40 degrees. 

Glyphosate--much vilified for its overuse in agriculture--is still the most dependable systemic herbicide to use. If close to wetlands, a wetland-safe formulation (not Roundup) can be used, though it takes some sleuthing on the internet to find it. For foliage, a 2% solution is good, but some use 4%. 

I've heard that some land managers use an herbicide called Milestone, which may be a useful alternative, particularly because it doesn't harm surrounding grasses. 

If you read online about lesser celandine, you'll sometimes see claims that it must be sprayed very early in spring, before it flowers. Early spraying in helpful, but people should not be deterred from spraying later in spring as well. You'll also see claims that lesser celandine might be mistaken for the native marsh marigold. But marsh marigold is extremely rare. In all my explorations of Princeton's open space, the only marsh marigolds I've seen are the few that I have planted. 

Lesser celandine reminds us that we are all connected. What one person allows to grow in the yard can impact neighbors and nearby natural areas. The more a neighborhood becomes infested, the more likely it will spread to your own yard, through landscapers' mowers or on the hooves of deer. Thus, one person's problem quickly becomes other people's problem. It's important to be vigilant. 

Last Chance to Pull Stiltgrass

This week and maybe next are your last chance this year to pull stiltgrass (Microstegium vimineum). This mega-invasive is an annual, so the logic of countering its spread is to pull it before it can produce and drop seed. If the seeds haven't loosened yet at the end of the stalk, you can still pull it. Throw it in the trash, or if there's a lot, make a big pile of it so that any seeds that sprout the next year will all be in one place and easily covered or pulled. Definitely don't put it in your compost if its seeds are forming. If stiltgrass is just starting to invade your yard, pulling as completely as possible now will greatly limit its seedbank for next spring. Another strategy for large stands is to let the stiltgrass grow, then just as it begins to flower mow it short and hope its feeble roots don't have enough energy to grow another flowering stalk. 

For those fuzzy on identification, google lots of images, and look for the silver line running down the middle of the leaf. Stiltgrass can grow in the shade or sun, climb up to four feet, or thrive in a miniature state while ducking below your mower in the lawn. It's incredible survival skills include being incredibly inedible for wildlife. Stiltgrass gives nothing back to the habitats it increasingly dominates.

More on Stiltgrass, and a Success Story

Walking in the local woods, you've probably seen this kind of scene--what looks like a grassy meadow extending through the forest. In the filtered light of the understory, its simplicity and lushness may have some visual appeal. And yet, in some ways what you are looking at is the ecological equivalent of an urban food desert. 

Stiltgrass is an introduced plant that could be called a pervasive invasive, able to thrive most anywhere and dominate whole landscapes. Its success has come in part through being inedible. As wildlife selectively eat native vegetation, the stiltgrass expands, preventing the native plants from rebounding.

Unlike another nonnative annual weed that can look similar, crabgrass, stiltgrass becomes ubiquitous because it can thrive in sun or shade. That means the stiltgrass invading your lawn and flower beds can continue spreading ad nauseum into the nearby forest, or vice versa.

We used to call it bamboo grass--something in the shape of the leaves is reminiscent. The stiltgrass name refers to its angular growth, with each segment supporting the next as it climbs up and over fallen logs and other plants. Packing grass is another common name, referring to how it was once used to pack porcelain for shipment. That's probably how it first reached the U.S., in packing crates sent to Tennessee. 

When I first encountered it, growing on the bank of Ellerbe Creek in Durham, NC, I thought it graceful. Then came Hurricane Fran, bringing floods and fallen trees. In the aftermath of that massive disturbance, stiltgrass exploded in the landscape, expanding and ultimately choking forests with its vast, dense stands. New Jersey proved no different. 

Stiltgrass tends to establish itself along roadsides. Here it is growing in a green ribbon along Herrontown Road. Trails, too, provide an avenue for extending its reach, its tiny seeds carried on boots or the hooves of deer.

Though stiltgrass has covered large areas of woodland in the eastern U.S., we have found it worthwhile and even satisfying to counter its relentless incursions. Today in the Barden at Herrontown Woods, some volunteers pulled it out of a patch of native jewelweed along the edge of the parking lot. 

Nearby, on land where we have largely eliminated a massive clone of wisteria, stiltgrass was starting to move into the void. If nothing were done, this open woodland would have become a pasture of stiltgrass. But we have acted early enough to be able to remove all of this year's stiltgrass, dramatically reducing the seeds available for next year's crop. This photo shows the last patch before we pulled it. 

Interestingly, there are native grasses that look a little like stiltgrass, the main one being Virginia cutgrass (white grass), Leersia virginica. It has longer, narrower leaves that lack the silver stripe down the middle. As is a common ecological refrain, the native grasses "play well with others," not forming stiltgrass's massive, exclusionary stands. Some smartweeds like Lady's Thumb can also bear a resemblance. 

The Invasive Grass Fueling Wildfires in Hawaii

Hawaii didn't used to get pummeled by highly destructive wildfires. What has changed? A big part of the answer lies in the interaction between climate change and invasive species. 

Begin with a couple paragraphs buried in a NY Times article:

The area burned annually by wildfires in Hawaii has quadrupled in recent decades. Declining rainfall and rising temperatures have left the islands more susceptible to blazes, climatologists say.

Invasive grasses that are highly flammable have crowded out native vegetation in some areas, and climate change has exacerbated dry and hot conditions in the state, allowing wildfires to spread more quickly.

But what invasive species? A University of Hawaii website points to one that has been particularly destructive:

Guinea grass (Megathyrsus maximus), a nonnative invasive grass in Hawaii, forms dense stands that outcompete native plants and has very high fine fuel loads that greatly increase fire potential, spread, and severity.

Wikipedia describes guinea grass as a tough customer, growing ten feet tall. Though it can thrive in full sun, it can also tolerate shade, allowing it to invade native woodlands and thereby increase their vulnerability to fire during droughts. Native to Africa, the grass was introduced not only to Hawaii but also to south Texas.

How did guinea grass get to Hawaii (also spelled Hawai'i)? Wired provides an answer:

When Europeans arrived in the late 18th century and established plantations for growing sugarcane and pineapple, they also brought invasive grasses. Now the economics have changed, and those fields lie fallow. But the grasses have spread like a plague. “Those fire-prone invasive species fill in any gaps anywhere else—roadsides, in between communities, in between people’s homes, all over the place,” says Pickett. “At this point, 26 percent of our state is covered in these fire-prone grasses.”

This stuff is highly sensitive to short-term fluctuations in rainfall. The grass will grow like crazy when the rains come, then quickly desiccate when the landscape dries. “When we get these events like we’re seeing these past few days—when the relative humidity really drops low—all those fine fuels become very explosive,” says fire ecologist Clay Trauernicht of the University of Hawaiʻi at Mānoa.

An article in ABC News explains how the more intense and frequent fires affect the soil and human health: 

Elizabeth Pickett, co-executive director of the Hawaii Wildfire Management Organization, a nonprofit working with communities to prevent and mitigate fires, lamented the changes wrought by fire.

Invasive and fire-prone grass species have moved in over time and during a fire they can burn into native forests, which means the forests are replaced by more grass, Pickett said. The soil burns and sloughs off, leading to massive post-fire erosion that smothers coral, impacts fisheries and reduces the quality of the ocean water, she said.

The state is windy and the dust blows for years, harming human health, she added.

“When you lose your soil, it’s really hard to restore and replant. And then the only thing that can really handle living there in many cases are more of those invasive species,” Pickett said. “It’s systemic. Air, land and water are all impacted.”

A Philosophical Footnote

It's important to note that both climate change and the spread of invasive species are largely unintentional. Our world is threatened by excess carbon dioxide and other planet-heating gasses--lowly biproducts of our economy and lifestyles. We are used to thinking of collateral damage as minor and incidental, and tend not to judge people by what they do unintentionally. In fact, the cumulative impact of unintentional acts is the central threat we face. We live our days trapped in a predicament in which humanity, largely well-meaning, is allowed to collectively and unintentionally create problems, but not allowed to collectively and intentionally solve them. 

Additional reading: Thanks to a comment (see the critical comment and my response below), I found a couple more interesting articles about guinea grass. One gives a good overview of guinea grass as both an excellent, deeply rooted forage grass for cattle, and a weed that has disrupted ecosystems and croplands around the world. The other invests the grass with cultural connotations.

Other Invasive Grasses Fueling Fires in Hawaii

My friend Fairfax sent a link to another informative article that mentions three other introduced grass species fueling fires in Hawaii: fountain grass, buffel grass, and molasses grass. It also stresses that these and other highly flammable introduced grasses are altering fire ecology in the mainland U.S. as well.

What Guinea Grass Has in Common With Japanese Stiltgrass

Some people aren't aware the extent to which grasses affect our lives, for better and for worse. Corn is a grass, as are sugar cane, bamboo, and sorghum. In Princeton and up and down the east coast, the most dominant invasive grass is Japanese stiltgrass, which like guinea grass can grow in sun or shade, and uses what's called C4 photosynthesis to fix carbon from the atmosphere. Plants that use the C4 process--corn also being an example--are more efficient than other plants that use C3. Stiltgrass has invaded most areas of Princeton, growing from a zillion seeds each spring to blanket large expanses of woods. Wildlife don't eat it, so as it takes over, the landscape becomes increasingly inedible. I've long wished that someone would come up with a highly selective herbicide that would impact only C4 plants. If stiltgrass's impact on eastern habitats hasn't been sufficient to stimulate research, maybe the fire hazard in Hawaii will get researches to take a look.

A New Invasive Plant at Princeton High School

Here's a story about how an invasive nonnative plant can be accidentally introduced and quietly transform an area. It also shows how invasion can be regional but also very localized.

This is a big picture of a little yellow flower called birdsfoot trefoil (Lotus corniculatus). The clusters of flowers and especially the subsequent seedpods resemble the shape of bird's feet, and the tiny leaves echo this shape to some extent.

I hadn't knowingly seen it much, and only learned the name a couple years ago, but this year, 

it has spread aggressively along the grassy extension along Walnut Street at Princeton High School. I'd noticed a few the year before, but now it is dominant along a stretch in front of the Performing Arts wing and the Ecolab wetland. 

This year also, it is coating areas of an old pasture next to Herrontown Woods. In the pasture, it was probably planted intentionally as forage for cattle, but at the school, it surely was introduced accidentally.

Should we be concerned about either example of this nonnative rampancy? I sent an inquiry to a couple listserves of land managers, and received a tepid response. Birdsfoot trefoil is mostly a roadside weed, was the sentiment. It only gets a couple feet high, so will likely just stay in the background rather than stifle native species. 

But I have a vivid memory of a prairie walk I went on last year at the Kishwauketoe nature preserve in my home town in Wisconsin. At one point, leading us through a gloriously restored prairie, the botanist spotted a birdsfoot trefoil and immediately went over and pulled it out. Was it merely a pet peeve, or was his determination rooted in past observations of dramatic consequences if birdsfoot trefoil is allowed to spread? 

This short video shows how birdsfoot trefoil can alter the appearance, if not necessarily the composition, of a meadow:

I did a quick survey of school grounds and the nearby neighborhood by bicycle, and discovered that the infestation is limited to grass next to the extra wide sidewalks that were installed along Walnut Street a couple years ago. It probably hitchiked in on machinery or soil used in construction of the sidewalk. Another possible vector was the planting of new street trees right where the birdsfoot trefoil growth is now the most dense. Rootballs, topsoil, tools, heavy equipment--all can carry weedseeds.

This is an invasion that's in the very early stages, and could be easily nipped in the bud. For instance, I found a grand total of three plants on the middle school grounds. Five minutes of spot spraying with a selective herbicide now is all it would take to stop an infestation that will otherwise become intractable.

Another reason to take action is that it is poised to invade the new native meadow planting in the detention basin next to the tennis courts. In this photo, a few plants of birdsfoot trefoil grow just across the parking lot from the new native planting. Does the school want a native meadow, or a meadow that is thick with a nonnative species that appears capable of outcompeting many of the native grassland plants? 

Now, while the extent of the spread is limited, would be the time to take proactive action. 

Harrison Street Park: Contrasting Tales of Trees and Wildflowers

Most people drive by Harrison Street Park unawares. It's an old neighborhood park that lacks parking, and so mostly serves those who live close enough to walk there. Whenever I think to stop by this surprisingly spacious park close to Nassau Street, it's to check in on dreams living and remembered. 

One dream is bringing back the American chestnut. We've planted a number of chestnuts around town that are 15/16th native. They were originally crossed with a resistant asian chestnut, then backcrossed with the aim of ending up with a predominantly native chestnut tree that still carries the Asian species' resistance to chestnut blight. Some of these trees have proven susceptible to the blight, but two in particular have resisted the blight thus far. One of these is in Harrison Street Park, nearly 20 feet tall now. 

We also planted two native butternuts there, another native tree that has been marginalized by an introduced disease. It's good to see them thriving and starting to bear nuts. 

There's also an attempt by the town, successful thus far, to keep a grove of ash trees protected from the introduced Emerald Ash Borer, via systemic applications of insecticide. Another small grove of trees was planted through a citizen donation and collaboration with the Shade Tree Commission.

Other dreams for Harrison Street Park, involving wildflower plantings, have not done so well. Princeton Borough had great dreams for this park at one time. In 2006, they hired me to conduct an ecological assessment and write a stewardship plan. Then they hired a landscape architecture firm from Philadelphia to design improvements to the park. Neighbors offered many ideas and expressed many opinions. The old wading pool--a relic from a distant, more sustainable era when kids gathered in their neighborhood parks in the summer--was removed, the play equipment was updated, and a few new features were installed. 

Some $30,000 was spent on new native plantings that looked good for a year or two before going into steady decline. The idea was that neighbors would care for all these new plants. Of course, a drought promptly ensued. Some of the neighbors rose to the occasion to keep the plants going, but the extensive flower beds required more than an initial season of zeal. Neither the borough maintenance crews nor any of the neighbors had the training or interest to keep the flower beds weeded over the longterm. 

This flower bed is now a massive stand of Canada thistle and mugwort. 

The plant with the big leaves is a common weed in the midwest that is showing up more and more in Princeton. It looks like rhubarb, but is in fact burdock. 

There's a swale in the park that receives runoff from a private parking lot next door. These wet, sunny spots can tip the balance towards native species. A friend and I planted various floodplain species--joe pye weed, tall meadowrue, etc--but also planted Jerusalem artichoke, which is a native sunflower species with edible tubers. 

When planting an aggressive plant like a native sunflower, it's easy to believe one will follow up and keep its expansionist growth in check. That's almost never the case. The sunflowers has spread aggressively underground over the years, and have long since swallowed the other wildflowers in their dense growth. Each year the sunflower clone expands, as park crews mow around its fringe. 

We also planted a couple pawpaw trees there, but they were overwhelmed by the sunflowers. A couple black walnut trees sprouted on their own and had much better luck, somehow managing to rise above the sunflowers. Trees that plant themselves tend to be more successful than trees planted by people. On the upside, the sunflowers are so aggressive that they require no weeding, and there's a dazzling display of yellow in the fall. But, like some of the other plantings at Harrison St Park over the years, it's not what was originally envisioned. 

Poison Hemlock Popping Up in Princeton

When mathematician and Herrontown Woods volunteer Robert Budny reported that he had found lots of poison hemlock growing in his yard in Princeton, I was at first surprised. I somehow got it in my mind that he was talking about water hemlock--a rarely encountered native wildflower, of which I have come upon a grand total of one growing in Princeton's preserves. 

Robert was quite sure of his find, and said he'd experienced skin irritation while cutting the numerous plants down.

Then I saw this patch of white along Snowden, which too was surprising, since I pass there almost daily yet had never noticed before these tall plants covered in blooms. Maybe it was Robert's sharing of his backyard encounter that primed my eye to take notice.

These, too, proved to be poison hemlock, with broad disks of tiny white flowers. 

and lacy compound leaves. Other plants with white disks of flowers this time of year are the shrubs elderberry and silky dogwood, but they don't have finely dissected leaves like this poison hemlock. 

Though Princeton has many invasive species, those in the carrot family have been few. Goutweed spreads through some gardens. It gets mixed in with the intended plants and can be very hard to eradicate. My neighbor up the street was somehow able to do it, though, through sheer persistence. Wild carrot (Queen Anne's Lace) shows up occasionally along roadsides. It's a beautiful plant, but I've seen it become too much of a good thing in the midwest. Here's information on which members of the carrot family behave invasively in Wisconsin. It includes a useful description of this plant family.

"Many members of the carrot family (Apiaceae) are invasive in Wisconsin. These herbaceous biennials and perennials have alternate, compound leaves with sheaths at the base of leaves. Many small, 5-petaled flowers are arranged in compound umbels (several small umbels combine to make larger umbels). Of the species that are invasive, all have white flowers except wild parsnip, which has yellow flowers. Seeds form in pairs and stems are hollow at maturity."

There are other invasive plant species that, entrenched elsewhere in NJ, are just starting to show up in Princeton. Jetbead and Mile-a-Minute are examples. Catching these early and preventing them from spreading means fewer aggressive plants for gardeners and preserve managers to deal with in the future.

Related posts:

Pulling Jetbead

Mile-a-Minute Spreading into Princeton