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.

Holden Arboretum Studies Resistant Beech and Ash Trees

Herein lies a post about the long, patient work that begins when something goes wrong with the world. With the introduction of beech leaf disease into North America, things have gone very wrong. Another noble, native tree species, towering and strong, is proving no match for a microscopic nematode. When this happens--yet another example of collateral damage from international trade--scientists mobilize to seek understanding and possible remedies.

In recent blog posts about beech leaf disease, I've mentioned Holden Arboretum. Holden happens to be located east of Cleveland, close to where the disease was first noticed back in 2012. Visiting family in Cleveland this summer during a band tour, I reached out to Holden staff to see if I could stop by to witness their research on the disease. 

Tucked behind some 3000 acres of gardens and ponds, forests and fields, is a research station where Holden is devoting staff and greenhouses to a collaboration with the U.S. Forest Service and others to test resistance not only beech leaf disease, but also to the introduced insects that have decimated two other native trees--ash and hemlock. 

I learned primarily about their research on beech and ash trees.

AMERICAN BEECH

Where did the nematode that causes beech leaf disease come from? According to Rachel Kappler, Holden's Forest Health Collaborative Coordinator, who generously came in on a Saturday to give me a tour, they have identified the island in Japan from which the nematode came. It was not a species from Asia's mainland. 

Holden's main endeavor is to seek out beech that show some resistance to the disease, and test that resistance. 

Rachel first grows seedlings that can be used as root stock for these tests. The root stock serves as the bottom half of a graft.

When trees are found that have lingered in the landscape while others succumb, Rachel then grafts cuttings from these "suspiciously healthy" trees onto the prepared rootstock. 

Once the grafts heal,

the trees can be tested for resistance. Measured numbers of nematodes are applied to the buds, documented with colored tags, and the tree's resistance to the nematodes is then observed.

The nematodes are small enough to enter the buds between the overlapping bud scales. The tiny worm-like creatures inhabit the leaves all summer. Then in fall, exiting the leaves through the stomata--the openings on the undersides of the leaves through which the tree breathes--the nematodes transfer to the new buds to overwinter.

Each step in the process of testing resistance takes time and consistent attention. Rachel says some promising means of speeding research are in the works. Promisingly resistant trees can be propagated using only their leaves. The leaves are cut, a particular root hormone applied, then the leaf is stuck in soil medium to grow. This approach could potentially avoid the need to grow root stock, grafting, and the time it takes for grafts to heal.

As for treatments for the disease, she says soil applications of phosphite have mostly been experimented with on smaller trees because it's easier to study at these smaller scales. Similarly, using chemical sprays on the trees' foliage requires just the right timing, and a thorough coating, which makes larger trees very difficult and expensive to spray. They are experimenting with pruning to allow better air circulation and thereby reduce the moisture that the nematodes like.

ASH TREES

Research on resistant ash trees is a little farther along. Rachel showed me a grove of young green ash--protected by a deer fence--that are being tested for resistance to the Emerald Ash Borer (EAB), which spread through Ohio nine years before Beech Leaf Disease. This is the same introduced insect that has decimated Princeton's ash trees.

Rachel explained that the ash can defend themselves from the burrowing insects in three ways. One is a blockage that prevents entry. Another is to react by building a wall around an ash borer that has gotten in under the bark. Another is to somehow deprive the ash borer of nutrition, so that it becomes stunted. 

Sticky boards are used to monitor the presence of Emerald Ash Borers at the site.

When I told her that I had only seen one adult Emerald Ash Borer in my life, despite the hundreds of millions of ash trees killed, she pulled one off of the sticky board.

In this closeup, the Emerald Ash Borer is on the left; a native ash borer, far less destructive, is on the right. Though they are similar in appearance, it's the difference in behavior of the introduced species that has proven lethal.

She said that ash trees become vulnerable to EAB attack fairly early in life, certainly under ten feet high. While some of the ash trees being tested in the grove are dying due to EAB (perhaps these are the controls in the experiment), 

many are doing well, showing some degree of resistance. 

The green ash that have proven resistant to the EAB must not only be able to survive at low EAB levels, but also when the Emerald Ash Borer is present in high numbers. Rigorous testing helps avoid later marketing an ash variety that ultimately could prove vulnerable. 

This scar is evidence of an inner struggle by the ash to fend off the borer. The tree tries to build walls around the EAB larvae. 

Rachel described an autoimmune reaction, observed in black ash up north, in which the tree is too aggressive in blocking off passages, interfering with its own circulation. 

She talked about the physical aspects of doing research on trees and their pathogens. The wooly adelgid that plagues our hemlocks is hard to study, in part because it can be hard to apply the soft insect to test trees without squashing its soft frame, so they use its eggs. Nematodes are much easier to count and apply to branches.

Expanded greenhouses suggest Holden is expanding its efforts to nurture trees resistant to imported insects and disease. 

One bonus from my visit was that Rachel took an interest in our efforts in Princeton to bring back the native butternut (Juglans cinerea), and has put us in touch with someone studying the species.

If, as beech leaf disease takes its toll on beech trees in Princeton, we see some trees that "linger" and remain "suspiciously healthy," we'll want to notify Holden Arboretum, to aid their ongoing search for resistant trees. 

A thunderstorm prevented me from exploring the many gardens at Holden that day, including a treetop walk and tower. And then there's the Cleveland Botanical Garden closer into town, with which Holden recently merged. These are some good botanical destinations in Cleveland, with a mission that extends far beyond the city, and an engaging origin story.

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

A Followup on Beech and other Threatened Native Trees

Having grown despondent about the devastating toll beech leaf disease will likely take on Princeton's beech trees, I was surprised and somewhat heartened by what I found on the Princeton University campus. 

A friend from childhood was visiting me for the first time, and as I showed him and his wife around campus, I began to feel as if we had somehow been transported back to an era before introduced pathogens and insects had marginalized many of our native trees.

An American white ash towered over us, healthy as can be. American elms, too, grew as if Dutch elm disease had never arrived.

Unlike the ailing beech trees up along the Princeton ridge, the beeches on campus appeared unfazed by beech leaf disease.

I looked for signs that these trees had been injected with chemicals to ward off invasion, but found none. Surely, though, this improbable survival depends heavily on medicinal intervention.

Since I first alerting the community to the presence of beech leaf disease in Princeton in a blog post and letter to the editor, some articles have been written in the local press--one in TapInto Princeton and one in Town Topics. 

Both mention phosphites as the primary treatment available thus far. Applied to the soil, phosphites are a biostimulant that improves the tree's immune system response. I was skeptical that this could make much of a difference, but the University appears to be having good results. Grounds supervisor EJ May said they started seeing signs of beech leaf disease two years ago. Speaking generally about efforts to save native trees, he acknowledged some losses but some success as well.  

Another lead I had checked out was a kind of beech mentioned in a list of special campus trees.  Called a fern-leaved beech (Fagus sylvatica 'Asplenifolia')--a variety of European beech with unusual foliage--the university had gone to great lengths to save this extraordinary specimen during construction of the new chemistry building. The tree's described online as having "no serious insect or disease problems." Was the text written before beech leaf disease was discovered in 2012, or might this variety have some sort of natural immunity? I stopped by to take a look, and could find no visible symptoms. 

There remains, too, an uncertainty as to the origin of the nematode that causes beech leaf disease. It is most similar to a species found in Japan, but differs in some ways. 

Witnessing a Spongy Moth Outbreak Along the Appalachian Trail

I wasn't expecting to run into an outbreak of spongy moths (formerly called gypsy moths) in New Jersey earlier this week. The aim of driving up to the Stokes State Forest near Delaware Water Gap was to drop off my younger daughter Anna so she could resume her thru-hike on the Appalachian Trail. 

After a couple day visit at home, Anna was eager to continue her journey northward towards Maine. When we reached Sunrise Mountain Overpass, she asked if I wanted to hike along with her for a bit. 

It was as if she had invited me into her home, which the AT has been since she began in Georgia back in late February--more than 1000 miles thus far. Everything she needs is in her backpack--designed to be lightweight but still very substantial--as she hikes up and down mountain after mountain, rain or sunshine, cold or hot, following America's verdant eastern spine through North Carolina, Tennessee, Virginia, West Virginia, Pennsylvania, and now just the northwestern tip of NJ before heading into New York state. 

Most of the inspiring vistas she sees along the way are not tempered with a warning about venomous snakes, like this one at the parking lot. New Jersey is unusual in having venemous snakes in the north and south of the state, but not where we live in central Jersey. As for black bears, over three months she has seen only one and heard another. Though she started the hike on her own, there's now a group of companions with whom she camps each night.

As we hiked the rocky trail, we had to look mostly down to avoid the stones, stealing glances at the high quality woodland, free from invasive plants except for an occasional garlic mustard. We soon became aware, however, of an odd noise that sounded like a light sprinkle, despite the clear sky. When I turned back, leaving Anna to head north on her many steps towards Maine, I started taking a closer look at the leaves of oak, sassafras, and maple above. The well-munched leaves were surely a very generous giving of tissue by the trees to the local insect population. 

But what was that sound of rain with no rainclouds in sight? And why was the ground littered with fragments of green leaves? Whatever was eating the trees was being messy about it. 

Then I felt something very light fall on my head. I brushed it onto my hand, gave it a good look, and decided to call it frass, that is, caterpillar droppings. 

On the ground all around, the leaf litter had been in turn littered with this frass, raining down from far above.

Though most of the caterpillars remained unseen high in the canopy, a few were close enough at hand to get a photo. 

Back home, searching the internet, the caterpillar's identity quickly became apparent: spongy moth, also known as Lymantria dispar dispar, and formally known as "gypsy moth."

One source described exactly our experience along the trail:

"(Spongy) moths are invasive insect pests that can be destructive to trees, especially hardwoods like oaks. In May and June, each caterpillar can grow up to two inches long and consume 11 square feet of leaves. Signs of a (spongy) moth outbreak include bare tree canopies, droppings that sound like rain, and leaf confetti on the forest floor."

If you haven't heard of spongy moths, or haven't heard of them in a long time, it's because this highly destructive introduced species is no longer causing widespread havoc in our forests. thanks to the development of a remarkably successful, low-toxicity treatment. 

Imported into Massachusetts from Europe in 1869 with the intent of starting a new silk industry in America, the spongy moth escaped into the wild and was soon causing dramatic defoliations of forests. Though oaks are a favorite, spongy moths threaten a broad range of species, including both hardwoods and conifers. One source alphabetically describes its diet this way:

Preferred: Alder, apple, aspen, basswood, birch, hawthorn, oaks, tamarack, willow, witch hazel
Intermediate: Beech, dogwood, elm, hemlock, maple, pine, Prunus species, serviceberry, spruce, walnut
Avoided: Ash, balsam fir, cedar, red & white, locusts, mountain maple, pine, scotch

According to numerous articles found on the Papers of Princeton website, 13 years of intense spraying led to eradication of the spongy moth in NJ by 1932, but it reappeared in 1953 and by 1955 had again become a serious pest. In 1965, a small area near Mt. Lucas Road in Princeton was sprayed. As defoliation increased statewide through the 1970s, the most common treatment--carbonyl, also known as Sevin--became suspect due to its effect on honeybees. 

Letters to the editor describe heroic citizen efforts to round up and destroy the moths' egg cases. Elizabeth Carrick, chairman of the Woodfield Reservation Committee, described a successful outing by girlscouts in 1972. In 1980, Preston and Helen Tuttle reported on a hand collection campaign in the Institute Woods that included renowned faculty at the Institute for Advanced Studies:

During the past two weekends. 95 individuals, ranging from Girl and Boy Scouts to world-famous mathematicians, took part In all. 8.791 egg cases were collected or immobilized witn a hand held sprayer containing a mixture of creosote, turpentine and transmission fluid This was used to spray those egg masses that were above convenient scraping and collecting reach Egg masses collected the first weekend were given to the state Biological Controls Laboratory to feed spongy moth predators being developed by the state.

Destruction peaked in 1981, when 12 million acres were affected by defoliation nationwide. The biggest reason we haven't heard much about this hugely destructive pest lately is the utilization of a low-toxicity bacteria called Bacillus thuringiensis (Bt). First mention of it in local papers appears to have been in 1974. Bt is sprayed on foliage in the spring. When eaten by the caterpillars, it disrupts their digestive systems. By 1990, arborist Sam deTuro of Woodwind Associates, who used to have a regular column in the Town Topics, was combining the traditional chemical spray methods with a new formulation of Bt.

Like the many mountains and valleys of the Appalachian Trail, moth numbers have risen and fallen dramatically through the decades. Spongy moth numbers in NJ reached a relative low in 1988, only to rise 19 fold in 1989. Another peak came in 2008, prompting aerial sprays of Bt in Princeton. 

Numbers have dropped since then, leading many of us to forget about spongy moths altogether. For that luxury, we have a state government program to thank. The New Jersey Dept. of Agriculture has been running a   spongy moth suppression program at least since 2007. In 2024, they planned to spray 3000 acres of local and state-owned land. The aim is to prevent repeated defoliation of forests. Trees that can survive defoliation one year may not be able to survive defoliation two years in a row. The state description sounds like what governments are supposed to do--work collaboratively to intervene in safe ways to protect us and our environment. LDD stands for the species name, Lymantria dispar dispar.

The New Jersey Department of Agriculture promotes an integrated pest management approach, which encourages natural controls to reduce LDD feeding and subsequent tree loss. However, when LDD cycles are at a peak, natural controls have difficulty in preventing severe defoliation. In these special cases, the Department recommends aerial spray treatments on residential and recreational areas using the selective, non-chemical insecticide, Bacillus thuringiensis.

The Department's LDD Suppression Program is a voluntary cooperative program involving New Jersey municipalities, county agencies, state agencies, and the USDA Forest Service.

17 miles down the trail, Anna was still hearing the curious rain of frass all around, Hopefully the state program of spongy moth suppression will continue to work--an all-too-rare example of successful containment of invasive species threatening our forests.

Below, some sights seen during my short hike on the Appalachian Trail:

Expanses of sedge meadow that can give healthy forests a natural park-like appearance.

The striped maple, Acer pennsylvanicum, is a little tree that grows all along the Appalachian Mountains.

If you hike northward on the AT with the spring, much of your journey will be graced with the blooms of Mountain laurel, Kalmia latifolia, abundant on rocky slopes.

Beech Leaf Disease Sweeps Across Princeton

Princeton is losing its beech trees.

We were feeling celebratory, having just completed a successful corporate workday in Herrontown Woods, when I happened to pass by this small branch of a beech tree along the red trail. The leaves were strangely contorted, with dark green stripes. I had heard distant rumblings about a disease of beech trees, but had managed to keep my head in the sand until that moment. 

Back home, diagnosis was but a google's search away. Similar images popped up on the screen, along with the name: Beech Leaf Disease. Tree maladies typically come with an acronym. Emerald ash borer is EAB. The dreaded asian longhorned beetle, which they've had some success keeping from spreading across the eastern U.S., is ALB. The Bacterial Leaf Scorch that afflicts pin and red oaks is BLS. Now there was a new one: BLD. 

For those unfamiliar with the American beech (Fagus grandifolia), it's a native tree related to oaks and chestnuts, with beautiful smooth gray bark. They can get very big and live for centuries. Thousands of them grow in Princeton, in the preserved forests along the Princeton ridge and on slopes above the Stony Brook. 

The "grandifolia" in the latin name refers to the leaves, which are larger than the leaves of European beeches. This photo shows some healthy leaves (on top) and the curled, darker green leaves that have been contorted by nematodes overwintering in the buds. Beech leaf disease is caused by these nematodes--tiny worms spread by birds or the wind. 

Viewed from beneath, the infected leaves show a curious striping of dark and light green. 

During a subsequent hike in Autumn Hill Reservation, I was astonished to find nearly all the beech trees affected--their leaves contorted, their crowns beginning to thin. Beech in Rogers Refuge are showing symptoms, and Mountain Lakes preserve is reportedly also affected. According to online sources, essentially all of our beech trees will be dead within ten years. The news comes exactly ten years after the first emerald ash borer was found in New Jersey, with the skeletons of ash trees still haunting our woodlands.

According to this map, on the Holden Arboretum website, the disease was first spotted near that arboretum in Ohio in 2012, and has spread in all directions, most rapidly eastward.

According to the Maryland Extension website, the microbe causing the disease is Litylenchus crenatae mccannii, a subspecies of a nematode found in Japan. As one would expect, the only beeches resistant to this particular nematode are those that coevolved with it in Japan. 

The Holden Arboretum website mentions a chemical treatment that is being tested. It is a compound that is sprayed on the tree in the fall just as the nematodes are moving from the leaves down into next year's buds. Unfortunately it is highly toxic. The snail's pace of tree research compared to the rapid development of Covid vaccines caused one friend to ask, "Where is science when we need it?" 

The loss of a tree species from the canopy has all sorts of impacts on wildlife. Ash, elm, and maples bear abundant seeds early in the season to feed on. Two of those three have been largely lost. Nut-bearing trees provide food in fall and winter. Gone from wildlife diets are chestnuts, bacterial leaf scorch is reducing oak production of acorns, and it now looks like beech nuts will become very rare. Websites detail the ecological web of connection and dependence that is unraveled by the loss of a tree species. 

A post last year by the Brandywine Conservancy in Pennsylvania provides a particularly chilling description of what is in store for eastern forests:

"As the disease progresses, leaves will become smaller in subsequent years, and it will seem like autumn in the summer as infected leaves brown and fall from the tree, resulting in thinned crowns and branch dieback. Eventually, BLD will cause beech trees to abort their buds, leading to the death of the tree. Young beech tree saplings die within 2–5 years of infection, while mature trees live a bit longer. Death from BLD is likely accelerated in beech trees stressed by drought or Beech Bark Disease, which is a different infection that involves scale insects and fungi."

Here's a writeup I found on beech bark disease, which also poses a mortal threat. 

I encourage people to visit favorite beech forests in the area sooner rather than later, to appreciate the now threatened beauty of this singular tree. Over the next few years, if you are fortunate enough to find one that remains healthy while others around it succumb, you should let people know. The Holden Arboretum site provides someone to contact.

Yesterday evening, I visited the fabulous congregation of European beech off of Elm Lane on Constitution Hill in western Princeton. The many trunks appear to all come from the original massive trunk in the middle. 

Seen from a distance, they appear to be separate trees, but more likely were either branches that touched the ground and took root, or sprouts from the original tree's massive root system.

You can see how some of the trunks still have a sort of navel, where the original branch from the "mother tree" was cut off.

Its leaves, smaller than those of the native beech, were  showing early signs of the disease.

Some of Princeton's most spectacular native beech trees grow in the Institute Woods. That will be my next stop--that and a hidden valley between the Princeton University chemistry building and Washington Road, where I found a mixed forest of 200 year old trees, part of the great American forest cathedral that, in unspeakable sadness, loses its towering pillars, one by one.

Here is how I concluded a recent letter to the editor in the Town Topics: 

Outrage is often triggered by the intentional cutting of trees. The highly visible spotted lanternfly caused a stir, yet has proven relatively innocuous. The biggest threats we face are neither visible nor intentional. The emerald ash borer is hidden behind bark. Nematodes are microscopic. Our machines’ climate-radicalizing carbon dioxide? Unintended and invisible.

There is so much joy still to experience, for me particularly in Herrontown Woods, and yet in the larger workings of the world, so much to grieve.

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.