Native Fall Color and Berries in Herrontown Woods

One vision being gradually realized at Herrontown Woods through the power of incrementalism is the transformation of the long boardwalk into a native plant corridor that will be especially attractive in spring and fall. The boardwalk, given the V-ful nickname of Voulevarde because it was built by chainsaw virtuoso Victorino and leads from the main parking lot up to Veblen House, was intentionally routed past some mature examples of native shrubs.

Arrowwood Viburnum has toothed leaves (thus the latin name Viburnum dentatum) and can turn a brilliant reddish color in fall. 

We're managing the corridor for an open woodland, so that enough sunlight can reach the understory to power abundant berry making by the native shrubs. The many Blackhaw Viburnums, named after their black berries ("haw" means berry, as in hawthorn), are a dramatic example. 

The preserve's largest winterberry shrub--a holly called Ilex verticillata--greets you along a bend in the Voulevarde with abundant red berries this time of year.  

One of the preserve's large highbush blueberry bushes--they tend to be loners persisting here and there in the preserve--also grows along the route, with bright orange fall color.

The largest native swamp rose (Rosa palustris) in the preserve is also near the trail, its single pink flowers emanating a heavenly fragrance on hot summer days. Its rose hips are bigger than those of the nonnative multiflora rose. While the invasive multiflora rose is ubiquitous in the preserve, there are only two native swamp roses found thus far across 150 acres, mostly because the swamp rose needs more consistently wet conditions to compete. We've started planting more of them, in wet spots that get some sun, to see if we can increase their numbers over time. Again, the battle cry: "Incrementalism!"

Beyond the boardwalk, up towards Veblen House, is a good example of a rare native shrub, variously called Hearts a' Bustin' or strawberry bush. The deer love it so much that we needed to cage it until it was tall enough to escape their browsing. Located in a partial forest clearing, it receives enough sun to develop abundant berries.

In the fall, its leaves turn white. Hearts a' Bustin' is a native euonymus (Euonymus americanus), rarely seen due to deer browsing, while the nonnative euonymus, burning bush, is ubiquitous in the preserve and largely shunned by the deer. Notice a recurring story?

Up at the horserun near Veblen House, these look like shrubs or small trees, their fall color backlit by late afternoon sun. They are in fact trumpet vines growing on some sort of structure placed there decades ago. 

A different angle shows the trumpet vine with the bright red of Virginia creeper in the foreground. Both are native vines that can be a little aggressive, but sufficient shade deprives them of the energy to be obnoxious, allowing us to enjoy their best traits without any need to keep them in line.

Virginia creeper has five leaflets to poison ivy's three. These leaves look like they've donated some of themselves to the insect world. 

The boulders in Herrontown Woods, bedecked by mosses and lichens, are reminiscent of whales whose gray skin has collected barnacles. Sweetgum leaves are particularly creative and varied with their fall color.

Also generous with fall color is the native winged sumac, which has started to pop up in areas where we remove invasives. They seem to be part of the soil's memory of past eras when the forest was younger, before the canopy closed and shrouded the ground in deep shade. 

Another source of beauty, noticed while removing dead ash trees near the Veblen House driveway, is the combination of the old evergreen cedar trees with the deep burgundy of young white oaks rising to ultimately fill the space left by the ash.

The loss of ash trees to the emerald ash borer is a profound tragedy, but if we can take advantage of the new openings in the canopy to reawaken a diversity of native shrubs and trees, there is at least some recompense. 

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.

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.

The Lost Forest of Rogers Refuge

This past November, I received a request to look at a lost forest in Princeton. 

The request came from what may be the oldest open space organization in town--the Friends of Rogers Refuge. Dating back to 1967, FORR has been working with the town, and the water company that owns the land just down from the Institute Woods, to sustain the refuge's role as premier habitat for a tremendous diversity of birds.

Over the years, I've been able to witness and collaborate with a progression of leaders who have overseen stewardship--the Southerlands, Tom Poole, the Spars, the Varians, and most recently David Padulo. 

At annual meetings, discussions have tended to focus on the refuge's central feature, the surprisingly extensive marsh--how to keep it wet enough and protect it from the super-aggressive Phragmitis.

But this year, concern now extends to the floodplain woodlands surrounding the marsh--also vital bird habitat. One of these woodlands, thriving four years ago, has lost its trees.

This was not a forest classically lost to logging. The trees were not cut down but rather strangled over the course of several years, then left standing, each tree a monument to its past life. 

Few have seen the now ubiquitous strangler, the Emerald Ash Borer accidentally introduced to the U.S. from Asia. It's larvae work quietly under cover of bark, feasting on the ash trees' circulatory tissues. 

That a whole forest could die speaks to how common ash trees once were. The most numerous tree in Princeton up until just a few years ago, comprising more than 10% of the tree cover, the ash tree's skeletons can be found throughout the canopy of residential and open space lands. Ash were particularly good at colonizing abandoned fields, to the point of dominating one area of what is now Rogers Refuge. 

As the botanist in an organization of birders, I was asked what the longterm prognosis for this lost forest might be. Winnie Spar, Joe Melton, and I walked the red trail to have a look.

One striking feature is what I call "poison ivy trees." These are dead trees, still standing, that have been scaled by poison ivy vines, with their classic "hairy is scary" stems. In order to bloom, poison ivy must climb a tree, sending out lateral flowering shoots along the way. The branch-like laterals give the tree the look of still being alive, even though all the leaves are now poison ivy. The flowers produce berries that, birders will enthusiastically tell you, serve as important food for birds.

Another feature of a lost forest is the shrub growth that now thrives on the infusion of sunlight previously claimed by the tree canopy. Much of this shrub growth, unfortunately, is nonnative and inedible to wildlife, like this Asian Photinia. At least it can be said that the invasive shrubs are not as thick at Rogers Refuge as they are at the Institute Woods just up the hill.

A few other native tree species fill a small portion of the void. In early November, the occasional silver maple and pin oak still had many of their leaves. Mixed in were a couple elms, and a red maple. 

Used to the numerous red maples at Herrontown Woods on the other side of town, I was surprised to find instead an abundance of box elder of every size growing in this broad floodplain of the Refuge. Related to maples, box elder are not the most statuesque of trees, but their soft wood can make good bird habitat. They now stand as the main hope for rebound in this patch of former forest. 

The walk being with such knowledgeable birders, attention never strayed far from bird life. We saw a couple pileated woodpeckers, a coopers hawk and a couple other larger hawks. Winnie kept up a running monologue about the status of this or that bird. Mockingbirds have been around for a long time, but the catbirds keep them out of their territories when they are present. While a warming climate is causing many birds to extend their ranges northward, ravens, surprisingly, are moving south. She's seen some in the Refuge. Warblers love something about the spicebush flowers, whether it's the flowers themselves or an insect in them. Blue gray knatcatchers were mentioned, along with many other bird names that didn't register in my botanical brain.

There's a lot of concern that last year's fires in Canada have been very hard on migrating birds that nest up there. A woman who catches and tags migrant birds had been having very few birds coming back down from Canada, but her catch/tag/release activity, conducted on Sundays, was hampered by rains every weekend this fall. One day she got only ten birds, total. 

But then Winnie is quick to add that she saw Cape May Warblers in the Refuge for the first time, several in fact, with immatures, and they too nest in Canada. Winnie is one to accent the positive, while acknowledging that migrant bird numbers are down 50-90%. 

This lost forest, the decline in bird numbers, accelerating changes in climate, democracy under threat--in many ways, America is losing its memory of what it once was. The soil, for its part, holds memory through the seeds that remain dormant within it. Back when the seed bank--this stockpile of seeds yet to sprout--was dominated by the seeds of native species, succession as an ecological phenomenon featured an orderly and predictable progression of species, from grassland to shrubland to mature forest. But the soil under our feet has lost its memory, whether by plow, development, intense browsing, or displacement of native species. Invasive lesser celandine, poisonous to wildlife, coats the ground in the spring, followed by inedible stiltgrass and its billions of seeds in late summer. Invasive shrubs and deer combine to limit native species and thwart the once timeless process of succession. Though the tree canopy is still dominated by natives, these are under increasing attack from introduced insects and disease.

Even healthy trees can be overwhelmed by vines of porcelainberry and wisteria.

Given the circumstances, it's fair to ask what sense there is in persevering. What I find is that the native growth force, if often smothered and badly abused, remains intact. When given a chance to prosper, native plants and wildlife still can thrive. In Rogers Refuge, we've seen a tremendous rebound of spicebush since the town began culling deer to reduce browsing pressure. That in turn has improved habitat for birds. FORR has paid contractors to successfully set back the Phragmitis and porcelainberry. 

Through periodic interventions over a number of years, the Varians have virtually eliminated the one patch of invasive Japanese knotweed at Rogers Refuge. 

We pick our spots, time our interventions strategically to have the most impact for the least amount of effort, and look for opportunities. Despite the tragedy of losing ash trees, the new openings in the canopy could potentially allow native shrubs to grow, flower and bear in ways they haven't since being shaded out decades ago. 

Our inherited environmental mindset is that nature, if protected from intentional depredations like logging and draining, will heal itself. As FORR's webmaster Laurie Larson points out, "when Charles H. Rogers and the Southerlands started birding the “Water Company” in the 60s and 70s it was a landfill." The initial fight was to put an end to dumping. But now, at Rogers Refuge and many other places, the main depredations (invasive species, climate change) are unintentional, and the healing must be helped along by intentional effort. That effort could seem a sacrifice, but the primary feeling is one of gratitude, for the chance to work with nature--the greatest and most generously creative collaborator of all. 

Where Have All the Spotted Lanternflies Gone?

Well, it's happened, at least in our neck of the woods.

Billed as a major calamity, the spotted lanterfly invasion has gone "poof" this year. Yes, the spotted nymphs could still be found clinging to the stems of Ailanthus sprouts at our Barden in Herrontown Woods. 

And a few adults were later seen perched on the rachis of Ailanthus leaves. We pulled the sprouts out of the ground to deprive them of this haven. Hard to say where they went after that.

Writing a post about lanternflies three years ago, I learned that numbers of the invasive insect had dropped in some areas of Pennsylvania five years after first being seen. Lanternflies first showed up in Princeton in 2018, and here we are five years later, with what appears to be a dramatic drop in numbers.

It's true that people gave themselves over to squashing the pesky bugs--leafhoppers, actually--in spirited ways. (This photo shows one of the more creative approaches.) Some think the unusual weather has had an effect. Insect numbers overall have been down, be it the pollinators on backyard flowers, the odorous house ants that used to invade our kitchen, or spotted lanternflies. But my guess is that it has been the full-time predators, feathered or with eight legs or six, that are to be most congratulated for stemming the explosion of spotted lanternflies. 

Just follow the trail of colorful wings that brightened a walk up towards Veblen House one day.

The most powerful contrast for me is between the invasions of emerald ash borer and spotted lanternfly. Since the emerald ashborer arrived, about ten years ago, I have yet to see a single adult ash borer in Princeton, and yet the devastation they have brought to the ash tree is all around us. The lanterfly, on the other hand, has been seen everywhere, and yet I can't point to a single plant that has died due to their appetites. We humans are visually oriented, but it's the invisible threats--be they an invasive insect or even more significantly an overdose of carbon dioxide--that most endanger our world.