Invasive Mile-a-Minute Spreading at Princeton Battlefield

Ever find yourself caring deeply about something the rest of the world ignores? We all pick our battles, and here's a really good one for the Friends of Princeton Battlefield and/or our governing institutions to pick.

Princeton has been graced in many ways of which it is not even aware, and one of those is the up-to-now absence of Mile-a-Minute, a thorny annual vine that grows up and over everything if allowed. Gardeners beware. This one's particularly nasty, and though it has gained a foothold in nearby areas, I've encountered it in only two locations in Princeton. One location is the Princeton Battlefield. The other is on the gravel road in to Rogers Refuge. Each year I pull it out, but by the time I remember to do it, a few of the vines' little blue berries have matured, so the infestation has been growing.

Obviously, my efforts are not enough. The town of Princeton has fortunately hired the NJ Invasive Species Strike Team in recent years to treat invasions by new species, but the Battlefield is state owned, and because of a lack of intervention it is now serving as a seed source that will affect all Princetonians, and not only for Mile-a-Minute.

Another issue at the Princeton Battlefield is the massive invasion by porcelainberry--a vine that rivals kudzu in its capacity to sprawl over anything and everything. Its overwhelming presence may seem to dwarf the problem with Mile-a-Minute, yet it can also be seen as proof that we really need to catch these invasions early, before they get out of control. Porcelainberry is not only at the Battlefield, but is also dominating large areas all along the Stonybrook in Princeton.

Here are the copious berries produced by porcelainberry vines as they smother the flowering dogwoods planted in 1976 for the nation's bicentennial. The berries turn pretty colors--blue, purple, pink, or white--thus the name, and the original appeal of the plant. But the plant has escaped the usual checks and balances that otherwise sustain balance in nature.

Birds eat the berries of porcelainberry and Mile-a-Minute, thus the concern that what's allowed to grow at the Battlefield will impact the rest of Princeton.

The Friends of the Battlefield group, by the way, has been doing a great job knocking out big stands of bamboo around the Clark House during its annual workday in April. Look in the distance in the photo and you'll see an open field, with only a small remnant of bamboo back near the woods.

But bamboo doesn't spread by seed, and so poses no threat beyond the Battlefield's borders. Volunteer sessions can slow down porcelainberry and Mile-a-Minute a bit, but for any lasting benefit, we need to get some professional intervention. Maybe the Friends of the Battlefield could apply for a grant.

In the meantime, be on the lookout for its distinctive triangular leaf, put on some gloves, and pull it out.

Nature at the Princeton Battlefield

(Thanks to those who commented. Scroll down for an update.)

As a lover of both nature and history, I experience the Princeton Battlefield differently than most. There's gratitude for its preservation, along with some grieving for the way the land is managed. Nature here is pushed to the fringes, as if to replicate a giant ballfield. But the battle took place on a working farm, not an athletic field. 

The Clark House has been restored, its 18th century charms highly valued. So why would the landscape not be similarly treated? In the winter of 1777, the soldiers would have been treading through corn stubble, or pasture, or an orchard. 

One answer would be that visitors and re-enactors benefit from a clean surface. The question then would be how much to mow and where, so that people could enjoy a lawn, but also have areas that evoke more a feeling of the 18th century. 

As I walk across the field, I feel a sense of space more than place. Perhaps if I tried I could feel grandeur, or solemnity. Graveyards are mowed, after all. A big sky and a big field help us to understand that something big happened here, when a nation was being born, its future stretching far off towards the horizon. Maybe the landscape works in some spiritual way to evoke freedom and possibility. But as I walk these hallowed grounds, I'm also feeling a sense of a long ways to go before reaching anything interesting. Okay. Perhaps that long trudge could generate some appreciation for the long overnight march of Washington's amateur army from Trenton to Princeton. 

One tree stands in the middle of the giant lawn, an offspring of the great Mercer Oak that had witnessed the battle and lived through two more centuries before falling to a windstorm in 2000. Trees growing at the time of a great battle are called witness trees. The soldiers who fought that pivotal battle are long gone, but centuries later a tree, especially the long-lived white oak, could still claim "I was there!"

The offspring was donated by Louise Morse, spouse of Marston Morse, a mathematician who Oswald Veblen helped bring to the nearby Institute for Advanced Study in the 1930s. It was Veblen's initiative to acquire the 600+ acres behind the Battlefield that later became the Institute Woods.

The sign tells the story of the white oak and General Mercer. What I've come to look at, though, is not the highly symbolic tree but a thin sliver of golden brown in the distance. 

Beyond the lawn, towards the back of the Battlefield, is a meadow that is mowed once a year. For some reason they mowed the edge of it this fall but have left the rest, perhaps as winter cover for wildlife.

Taking a closer look, I'm surprised to see that, among the blackberries and prairie grasses, goldenrods and asters, are myriad sassafras sprouts, most of them bright orange this time of year. The meadow is a giant clone of sassafras--one root system with ten thousand heads. Can't say I've ever seen that before. 

To the left of the field is a bedraggled woods, dominated by the skeletons of ash trees killed by the introduced Emerald ash borer. A heroic American tree species silently meets its demise.

Behind the Clark House, and also across Mercer Street to the left of the pillars, more signs of introduced invasive species abound. Rampant invasive porcelainberry is stifling the 1976 bicentennial plantings--flowering dogwoods and daffodils around the edge of the field. As is typical of the landscapes we daily tread, the Princeton Battlefield invests in mowing the grass, while leaving the unmowed areas untended and overrun. Each year the Sierra Club organizes a spirited volunteer day to battle against bamboo near the Clark House. In the past, I would lead a group to cut the aggressive porcelainberry vines off of the bicentennial flowering dogwoods, but it's hard to make lasting progress when unsupported by the state agency that views grounds maintenance of this state park as "mow and go." Now all I do is make annual visits to snuff out a small infestation of mile-a-minute I spotted some years back on the Battlefield grounds.

Surely the soldiers who fought here knew their plants better than most people do today, and would feel disoriented by today's massive lawn surrounded by alien weeds. If I were to envision a battlefield landscape that sought to provide a more historically authentic botanical and horticultural context, I'd imagine some portion of the massive lawn being given over to the sort of landscape the battle was actually fought upon--pasture, orchard, corn field, whatever research shows to have been likely at the time. Along the edges would be native forest rather than tangles of kudzu-like nonnative vines. 

According to its mission statement, the Princeton Battlefield Society seeks to "restore the lands and cultural landscape." Maybe once other admirable goals are achieved, someone in the group will get interested in showing people an authentic 1777 landscape, and get the state parks department to help in the effort.  

To acquire, protect, preserve, and restore

the lands and cultural landscape related

to the Battle of Princeton of 1777;

To enlarge and improve the

Princeton Battlefield State Park;

To educate the public about the Battle

of Princeton, the Ten Crucial Days,

and the American Revolution.

Update, Dec. 23, 2022 : It's not hard to find accounts of the chronic underfunding of maintenance for NJ's state park system. This cuts both ways for Princeton Battlefield State Park. It explains why invasive species run rampant along the fringes of the park, but doesn't explain the large investment in mowing. One could have a mowed area around the house and for the areas of the land used for re-enactments and other events, and for visitors to explore the park (we used to fly kites there). Surely that still leaves large areas that could be managed for meadow. 

Nearby the Institute for Advanced Study grounds provide an example of large areas requiring only an annual mowing. 

Ribbons of mowed grass through meadow at the Battlefield would not only reduce mowing but also invite visitors to explore the full extent of the park. Walking across a vast lawn gives little sense of progress, departure, or arrival, and thus doesn't encourage exploration the way a mowed path does. 

The current management, in which nature is either suppressed by mowing or neglected along the fringes, does not reflect the view of nature held by the battle's greatest hero. George Washington was, among many things, a farmer. He believed plants were so important to a nation's future that he "had a dream of a national botanic garden and was instrumental in establishing one on the National Mall in 1820." 

In our era, when most people suffer from plant blindness, it must seem incongruous that the United States Botanic Garden is located immediately adjacent to the U.S. Capitol building. Plant blindness, according to the botanists who coined the term, "results in a chronic inability to recognize the importance of plants in the biosphere and in human affairs."

With this in mind, some rethinking of how vegetation is managed at the Princeton Battlefield could add to the visitor's experience, and shift some funds from mindless mowing to a mindful restoration of a more historically authentic landscape.

Battlefield Ribbon Cutting, plus Mercer Oak Takes an Eating

An email from Kip Cherry of the Princeton Battlefield Society included an invitation to a special event at the Battlefield--a ribbon cutting to celebrate preservation of the D'Ambrisi property, Sept. 16 at 10am in front of the Colonnade. There will be speeches, refreshments, and a tour that includes a visit to two ponds on the tract. The public is welcome.

While the park itself is expanding by 4.6 acres, the Mercer Oak II at the battlefield is looking a little threadbare this summer. One of the progeny of the original Mercer Oak, transplanted after the original lost its last branches in a March windstorm in 2000, it has inherited an iconic position among Princeton's trees, with a wooden fence surrounding and interpretive signage to explain its significance. According to one website, the original Mercer Oak "became the symbol for Mercer County (named for the general), Princeton Township, the NJ Green Acres program, and other agencies."

The wooden fence may keep the lawn mowers at bay, but not the insects. Oaks, according to entomologist Douglas Tallamy, support a vast diversity of insect species, which in turn feed the bird world, particularly in spring when birds need a high protein diet to feed their young. Usually, this sharing of plant tissue with insects doesn't affect the appearance of the tree, but this year many of the leaves are stripped to their veins. Kip has sent a sample off to Rutgers for identification, but when I stopped by, there were no insects to be seen, only the consequences of their work earlier in the season.

My best guess, from an image search on google for similar leaf damage, is the species of cankerworm active in the spring.

Another white oak nearby on the battlefield is showing far more severe symptoms, the source of which is unknown.

Previous posts about the battlefield should show up at this link, or are searchable by typing "battlefield" into the search box. Writeups on other trees you might encounter at the battlefield include young 15/16th native chestnuts protected from mowers and deer by cages, the towering black locusts behind the Clark House (black locust is decay resistant and was popular for making fenceposts), two hicans (graft of pecan on hickory root stock), and the dogwoods lining the northwest field, contributed by the Dogwood Garden Club, that I keep trying to save from invasive vines.

Botanical Tributes at Princeton Battlefield Threatened

If the plaque commemorating those who died in the Battle of Princeton got overgrown by vines, people would understandably be upset. But how about botanical tributes at the Battlefield? Mercer Oak The Second is doing well, carefully protected by fencing and no doubt periodically checked for health.

But there are other trees planted in memory of the battle that have been abandoned to whatever fate may come their way. Not far from the Ionic Colonade pillars are flowering dogwoods that were planted all along the perimeter of the north field. Those to the right of the pillars are doing fine. Those on the left are being smothered by vines--mostly porcelain berry and wild grape.

Some are so badly blanketed that you can't tell a dogwood is there until you peak under the mass of vines and see the venerable trunk of the dogwood holding up the free-loading foliage.

In this photo, porcelain berry leaves are on top, grabbing the sunlight from the flowering dogwood leaves below. I liberated a few of the dogwoods from the smothering vines some years back, but they really won't be saved until their protection becomes hard-wired into the Battlefield's maintenance. Here, again, the focus on lawn mowing to the exclusion of all other aspects of grounds maintenance has allowed an attractive and meaningful planting to be badly neglected.

It's really very simple for a crew to go in, cut the vines at the ground, maybe spray a dab of 20% glyphosate on the cut stem, and preserve these historically important plantings. It might add a couple hours a year of maintenance time.

The dogwoods also provide nutritious berries well timed with fall migrations, that is, if they get enough sunlight to power the production of the berries.

There are other plantings at the battlefield that are threatened, but not by lack of maintenance. We had high hopes for this 15/16th native American chestnut, planted in front of the Clark House. It's nearly 30 feet high now,

but I was recently told by Bill Sachs that the canker on its trunk--caused by the chestnut blight that nearly wiped out chestnuts a century ago--is not healing, suggesting that the tree will eventually succumb. Though this particular tree came out of a breeding program meant to generate blight-resistant native chestnuts, only about half of the trees will actually show resistance. Of the four chestnuts planted at the battlefield, two have succumbed, and this one may as well.

The fourth, however, is doing fine,

and Bill has already planted two replacements for the ones that died.

A larger question is whether the Battlefield wants to look anything like it did at the time of the battle. There were no lawnmowers back then, unless you count livestock, and these turfgrasses are not native to America. It's great to have a nice surface to walk on, have picnics, fly a kite, re-enact. Keep some turf, but should the landscaping really have nothing to do with historic accuracy?

Many battlefields around the country have made an effort to restore their landscapes to better reflect the era in which a battle took place. Mowing is very time-intensive, and most of the turf here is never walked on. The open feel is nice, but that could be maintained by reducing somewhat the mowed expanse, and restoring native grassland in unused areas, with broad trails through them kept mowed so that people can have the experience of walking through an authentic 18th century meadow. An orchard, too, would add some authenticity. But again, this means that an institution must go beyond lawnmowing in its conception of what constitutes caring for a landscape.

Begin, at least, with the dogwoods.

Mile-a-Minute Found at Princeton Battlefield

As if the massive invasion of porcelainberry, the "Kudzu of the North", at the Princeton Battlefield were not enough, I just discovered a patch of Mile-a-Minute there. This is, fortunately, only my second sighting of the prickly, fast-growing invasive in Princeton. The first sighting was in August of 2007, when I spotted it in a flower bed across Harrison Street from the Princeton Shopping Center.

For that first patch, it was relatively easy to contact the owner and convince her that it needed to be removed. The patch at the Battlefield is somewhat larger, about ten feet square, and has already produced berries that could be transported by birds to other locations. The next step is to go back with a sturdy pair of leather gloves and trash bags, and remove every last bit.

That Mile-a-Minute has a small foothold at the Battlefield suggests that it could have popped up most anywhere else in Princeton, so keep an eye out. The plant is an annual with distinct triangular leaves and a prickly stem reminiscent of our native tear-thumb. It should be pulled out and, if it has berries, placed in a garbage bag and put out for the trash. DO NOT put it in the compost, because the berries could then be spread.

It should be noted just how vulnerable we are to invasions of this sort. The Emerald Ash Borer's arrival in Princeton is a prime example. Accidentally imported to southeastern Michigan twenty years ago, it became established and therefore impossible to eradicate, because there was no "early detection, rapid response". Maintenance of the Battlefield grounds consists of mowing. Anything in the plant world beyond lawn requiring intervention is thus left to the chance interest and commitment of volunteers without a budget.

I happened to notice the Mile-a-Minute vine while checking the status of the ornamental flowering dogwoods planted long ago along the edges of the northern field at the Battlefield. I've been cutting the vines off, most years, but the porcelainberry is becoming increasingly dominant, smothering many of the dogwoods and other trees along the field's edge.

Here's a dramatic example, a dogwood barely visible beneath an oppressive cloak of porcelainberry.

On a planetary level, climate change was detected, but many with power to act have lacked a basic understanding of the consequences of delay. Here's where a naturalist's experience with invasives, or even a backyard gardener's experience with weeds like stiltgrass, mock strawberry, or ground ivy, can give insight into the importance of quick response. A ten foot patch of Mile-a-Minute seems minor, but without action, its berries will spread and the problem will quickly become too intimidating to dare act against. Bureaucracies do this all the time, as with Burmese pythons in the Everglades. Early warnings are ignored, and the problem doesn't become officially recognized as a problem until it's too big to solve.

Meanwhile, the vast lawn continues to be mowed, offering a superficial reassurance to passersby that the landscape is under control.

Kudzu-Like Vine Surrounding Princeton Battlefield

This is a followup to a previous post about the Princeton Battlefield grounds. The vast mowed lawn gives the impression of order at the battlefield, but along the edges, there's a different story.

In a closeup, it's possible to see the reddening foliage of flowering dogwoods spaced along the woods' edge.

Likely planted many decades back to grace the battlefield's borders, those along the left side are now completely overgrown by vines.

Here, one dogwood branch (slight burgundy color on the right) is all that can be seen reaching out of a stifling blanket of exotic porcelain berry vine. (Porcelain berry is short for Ampelopsis brevipedunculata, a name as sprawling as its growth form.)

In addition to ornament, the dogwoods have traditionally provided abundant berries for migrating birds. Some internet research has yet to reveal whether the porcelain berries provide an adequately timed and nutritious substitute. Lipid (fat) content in the berries is important for sustaining the birds' energy, since lipids provide more energy than an equivalent weight of sugar. The shade of the vines will also limit dogwood blooms next spring (note the flower bud on the left).

All around the base of the dogwoods, a tangle of vines reach upwards--porcelain berry and oriental bittersweet, along with the native wild grape.

It's easy to liberate a tree from vines. Simply sever the stems of the vines and leave the top portion to die. No need to pull anything down.

Elsewhere at the battlefield, on the south side of Mercer Road, more advanced stands of porcelain berry demonstrate the plant's kudzu-like capacity to overwhelm trees and shrubs.

These three trees and the surrounding landscape behind Clark House have completely disappeared beneath a blanket of porcelain berry. The one native seen was jewelweed, somehow able to poke a few of its orange flowers up through the enveloping vines sprawling across the ground.

Princetonians may want to develop a taste for grand-scale topiary, because the battlefield and the local birds are serving as a seed distribution service for this highly invasive species.

Dogwood Rescue at Princeton Battlefield

In the foreground is a thick stem of wild grape vine, angling from left to right. Just behind it is a dogwood tree laden with vines. Beyond are the pillars and lawn of the Princeton Battlefield. There's symbolism in the wild grape's angle, like those circular symbols with a line angling across that mean "No!". Some fifteen dogwoods lining the edge of the Battlefield are being suffocated by the vines.

And there's symbolism in the dogwoods, which were donated to the Battlefield by the Dogwood Garden Club of Princeton, and planted in 1976 as part of the nation's bicentennial. The trees will be turning 40 next year, that is if they don't all get buried alive by the rampant growth of vines.

Sounds like a job for Mr. Sustainable, who stopped by this past week, ready to rescue the beleaguered trees with loppers and saw. The rough customers were, from left to right, wild grape, poison ivy (that little, hairy section that looks like a caterpillar), multiflora rose, porcelainberry, and asiatic bittersweet. Also present but somehow left out of the photograph were english ivy and Japanese honeysuckle. Together they could be called the Serious Seven.

Mr. Sustainable found evidence of previous visitors who might have come to save the trees only to be pulled down by barley and another vine, hops, before they could counter this poison ivy's hairy embrace of the dogwood trunk.

You can see the cobbly bark of the dogwood underneath this web of vines crawling upon it.

Some of the trees were really beaten up, not only by vines but also by the fallen limbs of towering white pines planted just behind them.

Underneath that mass of vines was a trunk warped by the weight and deprived of sunlight.

Here's a healthier specimen, planted closer to the street. In the distance is the Mercer Oak 2, whose symbolism eclipses all others on the property. It was a good day for Mr. Sustainable--a couple hours spent liberating fifteen dogwoods from viney oppression. A more thorough job, for someone else, would take much longer and involve limbing up the pine trees and doing much more to discourage the vines from a resurgence. Until then, the dogwoods will occupy a world, as in The Incredibles, that refuses to stay saved for long. But at least the the trees have a chance to rebound, and still grace the battlefield with spring flowers when they turn forty.

Hybridized Time and Plants Meet at the Battlefield

Under the spreading hican tree (a grafting of a hickory/pecan hybrid to the rootstock of a hickory), John Mills hybridized past and present at his annual reading of the Declaration of Independence. The reading, along with some shootings of cannons and cooking of colonial foods, took place as they always do on July 4 at Princeton Battlefield. Soldiers explained the difference between a musket and a rifle, and said the rifles' better accuracy made it possible for the colonists to pick off British officers--something the British took as a breach of their gentlemanly rules of warfare.

The battlefield grounds now have a few new hybrids--four young chestnut trees that are 15/16th American Chestnut and 1/16th Japanese. The trees have three things going for them: a sunny spot to grow, the t.l.c. of Princetonian Bill Sachs, who planted them and is now keeping them watered through the extended drought, and immunity from Chestnut Blight that the Japanese portion of their genetic makeup will hopefully confer. The trees are part of a larger effort to reintroduce native chestnuts into the American landscape.

(You can read more about American chestnut tree reintroductions in Princeton by typing "chestnut" into the search box at the upper left hand corner of this blog.

Being a promoter of habitat for wildlife, I was a bit chagrined to see that the battlefield meadow (back left in the photo), which is normally allowed to grow through the summer, has been mowed down. A long-range goal of the Friends of the battlefield is to restore a more authentic landscape, which would likely mean replacing some of the mowed grass with orchards and meadows.