Native Trees of Princeton

An attentive reader commented that the page for "Native Trees of Princeton", which I thought I had added along the top of the homepage, does not exist. Funny, I clicked on the "publish" button but the list of trees refused to publish, nor did it magically publish itself during the ensuing weeks when my mind was on other things. Maybe Googles ever more sophisticated software detected that it still needed work, which is to say it was a bit "drafty".

Here it is, nonetheless, published as a post rather than one of those enduring "pages" at the top of the blog. It was created as a step towards fleshing out, or foliating, a rather bare tree list we have on the Princeton Shade Tree Commission website.

My apologies to any native tree species not included here. Please speak up. Catalpas, we'll talk.

ATTRIBUTES OF SOME NATIVE TREES IN PRINCETON 

This is an extensive but informal list of native trees you may encounter in the wild or in your yard, with some description, based on ten years of observation. 

Acer negundo (box elder)--Grows wild. Not commonly planted. It's soft wood can provide good habitat for birds. Considered messy and not very well formed.

Acer rubrum (red maple)--A durable, very commonly planted street tree. Also common in the wild.

Acer saccharinum (silver maple)--Common in yards and in the wild. Not often intentionally planted. Has a reputation for dropping limbs, but performs well in many yards, providing an attractive, open shade.

Acer saccharum (sugar maple)--Less common, but a sturdy, attractive native.

Amelanchier canadensis (shadblow, shadbush, serviceberry, Juneberry)--A very small tree or large bush. White flowers early in spring, supposedly when the shad are surging up the Delaware. Berries edible, but frequently attacked by cedar apple rust, so don't get your hopes up. Even our resident catbirds were disappointed.

Asimina triloba (pawpaw)--Small tree, up to thirty feet. I heard there's a wild stand behind someone's house down across Carnegie Lake, and a substantial patch in a park over in Cranbury. Plant more than one to increase prospects for the often elusive fruit. They clone, so best planted where there's a little room to expand.

Betula lenta (cherry birch)--Grows wild along the Princeton ridge. Not commonly planted in yards.

Betula nigra (river birch)--Beautiful bark and form, frequently sold with three trunks.

Betula (paper and grey birches)--These species are more characteristic further north.

Carpinus caroliniana (blue beech, hornbeam, musclewood)--Common along the Princeton ridge. Not often intentionally planted.

Carya alba (mockernut hickory)

Carya cordiformis (bitternut, swamp hickory)

Carya ovata (shagbark hickory)--Hickories are common in the wild, but not frequently planted.

Castanea dentata (American chestnut)--Devastated by the imported chestnut blight in the early 20th century. Only a few small specimens persist in the wild. The disease does not kill the root, which then resprouts. Backcrossing has developed resistant native varieties with a small percentage of asian genes, e.g. 1/16th Chinese. Some of these 15/16th native trees have been planted in parks and preserves in Princeton in an effort to reestablish the species. A few chestnuts grow along streets in Princeton, but are either Chinese or Japanese. The nut husks are very large and prickly.

Celtis occidentalis (hackberry, sugarberry)--Sturdy native, infrequently seen in the wild, underutilized in planted landscapes. They line Walnut Street across from JW Middleschool.

Chionanthus virginicus (fringe tree)--Very attractive flowers. Small tree/large shrub. Some evidence in Ohio that it can be attacked by emerald ash borer, but more evidence is needed before deciding not to plant.

Cornus florida (flowering dogwood)--Attractive small tree, commonly planted, with berries that provide important nourishment for birds migrating south in the fall. Fairly common in the wild, but an imported fungus has cut back on its numbers. It can be harder to establish that the Korean dogwood, whose fruit are eaten by monkeys in its native Asia.

Crataegus crus-galli (cockspur hawthorn)--Attractive small tree. Rarely found in the wild. Underutilized in planted landscapes, perhaps because of thorns.

Diospyros virginiana (persimmon)--Attractive mid-sized tree. Females bear fruit, which may be appreciated or viewed as messy.

Fagus grandifolia var. caroliniana (beech)

Fagus grandifolia var. grandifolia (beech)--Beech trees are common in the wild along the Princeton ridge, but are seldom if ever planted.

Fraxinus americana (white ash)--Princeton's most common tree, soon to be decimated by the arrival of Emerald ash borer. Though typically encountered in second growth forest, it can grow to a towering height, with a few extraordinary specimens to be found on campus and in older neighborhoods. Planting ash is discouraged, since all ash species will soon be dependent on chemical injections for survival. Anyone owning an ash they wish to keep should get it treated, with emamectin being the most frequently recommended insecticide to inject into the trunk.

Fraxinus pennsylvanica (green ash)--Usually found in wetter conditions, and less attractively shaped, than the white ash. Same susceptibility to emerald ash borer.

Gleditsia triacanthos (honey locust)--The wild variety has thorns and is rarely encountered, perhaps because it was spread by now extinct megafauna. The unripe seed pods have a sweet, edible inner lining. One large specimen can be found near the old gas station at Princeton Shopping Center. Planted varieties, such as those at the new Dinky station and Hinds Plaza, have no thorns, and provide a pleasant, open shade. The tiny leaflets conveniently disappear back into the lawn in the fall.

Gymnocladus dioicus (Kentucky coffee tree)--A remarkable tree, rarely found in the wild, for reasons similar to honey locust. Its very large compound leaves emerge late in spring, and drop early in fall, making the tree ideal for planting on the south side of passive solar houses. They were used in the landscaping for the Dinky parking lot.

Hamamelis virginiana (witch hazel)--Attractive small tree/large shrub. The native species flowers in late autumn, while asian species flower in the spring.

Juglans cinerea (butternut)--Rarely seen. Some are hybrids. The native species has suffered from the introduction of a fungal disease. Efforts are underway to bring back the butternut in Princeton, in parks and nature preserves.

Juglans nigra (black walnut)--Common in some wild areas, and in some backyards. Rarely planted, due to large nuts and the juglone compound emitted by the roots, which can suppress growth of tomatoes and other plants.

Liquidambar styraciflua (sweet gum)--Sturdy, large tree, common in the wild and sometimes planted intentionally. The "gum balls" it drops can be a drawback for some.

Liriodendron tulipifera (tulip tree)--Fast growing, long-lived tree that can reach great size. Flowers tulip-like and attractive, but usually too high up to appreciate. Common in the wild, but not typically planted intentionally.

Magnolia virginiana (sweetbay, swampbay)--Small tree. Can have attractive flowers. Not typically planted along streets.

Morus rubra (red mulberry)--The white mulberry (M. alba, nonnative) is also found in Princeton. A small tree. Bears abundant, edible berries similar in appearance to blackberries. The berries can be messy, and the tree lacks an attractive form. Very tasty berries, though, if you can reach them.

Nyssa sylvatica (black gum, tupelo)--Beautiful fall color. Sporadically encountered in the wild. Long-lived, sturdy. Is becoming more frequently planted along streets.

Ostrya virginiana (ironwood, hophornbeam)--Small tree. Not common in the wild, nor in the landscape trade.

Oxydendrum arboreum (sourwood)--Small tree with bright red fall foliage. Craggy form. Underutilized; may not be well adapted for the nursery trade. More common in the wild further south. Several specimens in Princeton, including one next to the church across from the high school.

Platanus occidentalis (sycamore, plane-tree)--Can be confused with the London planetree, which is a hybrid between two species, one of which is P. occidentalis. Attractive, large tree, with highly ornamental bark. Its more susceptible to anthracnose than the hybrid.

Prunus pensylvanica (fire or pin cherry)

Prunus serotina (black cherry)--The native cherries are attractive mid-sized trees typically found in earlier successional forests. They nearly rival oaks in the diversity of insects they provide food for, and so are very important for food chains.

Quercus alba (white oak)--One of the most majestic trees. The white oak "family" (those with rounded lobes, such as white oak, swamp white oak, and willow oak) are less susceptible to bacterial leaf scorch than the red and pin oaks (pointed lobes).

Quercus bicolor (swamp white oak)--Sometimes planted along streets.

Quercus coccinea (scarlet oak)--Attractive, but less commonly planted.

Quercus palustris (pin oak)--Very common street tree in Princeton. Its lower branches characteristically angle downward and often die back. Many are being lost to bacterial leaf scorch, which causes gradual dieback.

Quercus phellos (willow oak)--More frequently planted than in the past. More common in states further south. Its narrow leaves can form an attractive mulch, somewhat like pine needles.

Quercus rubra (red oak)--Common tree in the wild and along streets. Susceptible to bacterial leaf scorch.

Quercus velutina (black oak)--Encountered in the wild. Less commonly planted than red oak.

Robinia pseudoacacia (black locust)--Native to the Appalachians. Widely planted and naturalized elsewhere. Its wood is resistant to decay, it has attractive flowers, and can achieve a very attractive form with dark, craggy limbs contrasting with the foliage. Can be invasive in some habitats, and can clone, sending up young shoots armed with thorns. But some specimens in Princeton front yards are beautifully formed and well behaved.

Salix nigra (black willow)--Fast growing. Sometimes planted in low areas in the belief that it will dry the soil out.

Sassafras albidum (sassafras)--Attractive tree, common in the wild. Can clone, which may be why it's not commonly planted.

Tilia americana (American linden, basswood)--Attractive. Underutilized. Sporadically encountered in the wild. Linden trees along streets are generally not the native species.

Ulmus americana (American elm)--Though the elm was hit hard across America by Dutch elm disease, Princeton varieties have shown considerable resistance, allowing specimens to perform well and provide shade for many years, even though they may eventually succumb.

Ulmus rubra (red elm, slippery elm)


Native Evergreen Trees:

Ilex opaca (American holly, Christmas holly)--Attractive native, sometimes used in yards. Can grow eventually to 30 feet or so.

Juniperus virginiana (eastern red cedar)--Small tree. Useful in some situations.

Pinus strobus (eastern white pine)--Not encountered in the wild unless in planted stands. Its native range is to the north of Princeton. Can get big, and tends to drop large branches during ice storms.

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.

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.

The Viburnum Leaf Beetle's Gathering Harm

This fall, before the leaves fall off, check any Viburnum shrubs you know and love, whether in your yard or in your favorite nature preserve. Do the leaves look like this, pitted with holes, or even stripped down to the veins?

Most people have heard by now about the Emerald Ash Borer's rapidly multiplying demolition of our ash trees. Lest that devastation not be enough ecological and horticultural tragedy to absorb, there is another invasion underway in Princeton, by the Viburnum leaf beetle. This one--a European insect that first showed up in Canada before spreading to the U.S., is going after our understory, one Viburnum species at a time.

This and the above photo are of Viburnum dentatum, the arrowwood Viburnum, which grows here and there in our woodlands, preferring wetter soils. The light damage could have been done by a native insect, or by the first few Viburnum leaf beetles to show up, suggesting much greater damage the next year. Listed as "highly susceptible" on Cornell's website, the arrowwood Viburnum will be the first to succumb.

The maple leafed viburnum, frequently encountered along the Princeton ridge, is less susceptible and thus isn't showing any damage this year. As the Viburnum leaf beetle increases in numbers and exhausts the most susceptible species through complete defoliation, it will presumably begin attacking those that are less susceptible.

We are not completely helpless as yet another careless introduction to the continent wreaks slow motion havoc. This site offers some ways to prevent the beetles and their larvae from consuming your favorite specimens. As with all environmental damage done, the ecological and aesthetic services these shrubs were providing for free will now start coming with a price tag for human maintenance.

The Cornell site offers another ray of hope. An extension official in Rochester, NY asserts that even highly susceptible species may in the long term become viable again, as predatory insects and soil nematodes build up to prey on the Viburnum leaf beetles. Then, perhaps, the introduced species would come into some sort of ecological balance, doing some damage but not enough to kill the Viburnums.

It's a perfectly logical and reassuring scenario, and yet observation often brings into question the speed and effectiveness of nature's capacity to restore balance and sustain diversity. More often, invasive species remain dominant and destructive, be they Phragmitis, or Japanese stiltgrass, or porcelainberry. I called up the Frick Park Environmental Center in Pittsburgh, where I had first witnessed the devastating impact of Viburnum leaf beetle a decade ago. Asked whether they had seen any signs of balance being restored, they answered, "Not yet."

Related links:

The Pennsylvania extension service also has some useful information.

Past NatureNotes posts about the Viburnum leaf beetle, dating back to 2013, can be found here.

This post explores the likely aftermath of the Emerald Ash Borer invasion currently underway.

Spotted Lanternfly in Princeton

Most people by now have heard of the spotted lanternfly, an insect native to China, Vietnam and parts of India that somehow showed up in eastern Pennsylvania in 2014. A leaf hopper with distinctive markings and colorful wings, it spread rapidly as it sucked the juices out of grape vines, orchards, and trees like Ailanthus, black walnut, maple and red oak.

Two years ago, local papers reported a sighting of spotted lanternfly in northeastern Princeton. Last year, the summer of 2019, a couple friends reported seeing it in Princeton--Mimi found a few in her backyard in western Princeton; Scott saw some in Herrontown Woods near the parking lot. 

For me, it didn't become real until I encountered this curiously tilted nymph on a butternut tree leaf near Veblen House in Herrontown Woods in early July. A Penn State Extension post describes the insect's colorful development from egg to nymph to the winged adults that emerge in late July.

For some reason, I had avoided writing about the spotted lanternfly. Maybe I was maxed out on the world's problems, and didn't really want to delve into the prospect of yet another introduced insect wreaking environmental havoc. 

Unlike the Emerald ash borer, which has gone largely unseen as it skeletonizes our vistas, quietly killing every untreated ash tree in Princeton, 

the spotted lanternfly sounded poised to make a highly visible and messy invasion. The PA Dept. of Agriculture published a pdf with graphic photos showing mildewed foliage and tree trunks covered with the adult insects. And because plant juice is very dilute, the sucking insects need to move a lot of juice through their bodies to get the nutrition they need. That means that both nymphs and adults expel large amounts of "honeydew", which drops down from the trees and vines, and coats foliage on the ground with sugary liquid, promoting the growth of mold. Their egg cases look like mud, affixed to trees or cars or most anything. It sounded like our habitat restorations and garden beautifications would be reduced to a tattered, moldy mess.

Below are compiled some research and experiences with spotted lanternfly this past weekend at Herrontown Woods. 

Ailanthus--the Spotted Lanternfly's favorite food

Turns out that the spotted lanternfly has a strong preference for sucking the juices of Tree of Heaven (Ailanthus altissima). Native to China, Ailanthus is fairly common in Princeton and can be invasive, forming clones and sprouting aggressively from its roots if cut down. A stand of Ailanthus can be used for trapping the spotted lanternfly. Penn State extension offers tips for homeowners on this. 

At the Herrontown Woods botanical garden, next to the parking lot, we have an Ailanthus growing, and sure enough, some adult lanternflies were found clinging to its bark.

Looking up, the Ailanthus leaves appear to be getting eaten, though the lanternflies are said only to suck from the trunk and the stems, not the thinner tissue of the leaves themselves. 

In a sense, the preference for Ailanthus is good news. An invasive tree is being attacked by a newly introduced insect from a similar region of the world. But the tree is also helping the insect expand its numbers through the summer, and toxic compounds in Ailanthus, when ingested by the lanternfly, may confer some protection from predators.

The lanternfly's honeydew is causing sooty mold to grow on the plants underneath the tree.  The NJ Dept. of Agriculture info sheet reports that the sap dripping from "weeping wounds" on tree trunks can attract stinging insects. 

Probably the best thing to do is to take down the Ailanthus, using techniques described here.

More advice for homeowners

There's an enjoyable and clever article on various tactics on the MercerMe site. For instance, the adults are very quick to jump if you try to squash them. The article says their reflexes slow down with persistent efforts, however. Will test that next time. 

Utilizing more finesse is a trap a Pennsylvania teenager came up with after watching the lanternflies climbing the trunks of trees. She ringed the tree with tin foil to channel the ascending insects into a bag, where they would die within 24 hours. Another thorough read for homeowners is at this link, including a test to see if chickens would eat them. They didn't,

but something is clearly eating them, as these wings at Herrontown Woods show. 

Longterm prognosis

Will the spotted lanternfly prove to be a longterm calamity, like the Emerald ash borer, or fade into the background as a passing problem? Will it be a lasting plague for vineyards and apple orchards? An article reports that few lanternflies were seen this year in the area of Pennsylvania where it was first discovered five years prior.  Local Princeton arborist Bob Wells is quoted in the Town Topics as saying that though vineyards and apple growers have reason for concern, for homeowners the insect "won't be much of a threat at all." I inquired on a listserve that includes land managers in Pennsylvania who have had the insect around for several years now, and got mixed responses. One observed reduced numbers one year, then a rebound the next. 

It can be hard to know if you have spotted lanternfly in your trees. My friend LisaB, who lives near Herrontown Woods, had a couple black oaks fall near her property in late July, and was surprised to find numerous SLF nymphs on the leaves that until then had been elevated 70 feet above the ground. She had seen none in her yard up to that point. Her photos show the last nymph stage (red), 

  

and a beautifully captured example of what a newly formed adult looks like. Documented in past posts on this blog, insects like cicadas, butterflies, and apparently spotted lanternflies as well, must hang down as they unfurl their new wings. If the wings brush up against any obstruction, they can easily become misshapened. 

Update, Aug. 6: Walking through Quarry Park, closer to downtown, I noticed some Ailanthus trees near Spruce Circle,  looked up at the leaves above, and saw them there as well, a few scattered adults sucking juice from the rachis of the compound leaves. Will the spotted lanternfly be background or foreground, a quiet addition or serious pest? Time will tell. 

In the meantime, it looks like removing Ailanthus trees would be the most straightforward way to limit this new arrival's numbers and impact.

Reporting: I tried reporting the Herrontown Woods and Quarry Park sightings. The email address bounced, and the telephone number is always busy. It may be that the state doesn't want to hear about sightings in counties where the insect is already present, or maybe it's so widespread by now that the information isn't helpful.

Does milkweed kill lanternflies?

On the leaves of common milkweed growing near our Ailanthus tree, I found several lanternflies belly up or immobilized, leading to speculation that the insects sucked juices from the milkweed and died from the toxins therein. Apparently, as an introduced species, they have yet to evolve an aversion to the plant.

Reading the Landscape Along the Towpath -- Early Spring

One place that gets a lot more interesting if you know plants is the towpath along the Delaware and Raritan Canal. For those into reading the landscape, the section just upstream of Harrison Street in Princeton makes for a good read, packed with history, beauty, poignancy, and the drama of invasion. 

First, there's the water, here with branches of elderberry reaching out over the canal in the foreground. Elderberry characteristically sprouts leaves earlier than other native shrubs. Water teaches the richness that reflection can bring to life. 

Along this stretch of towpath, the strip of land between the canal and Carnegie Lake widens, making enough room for a nature trail loop that for nearly 20 years has given hikers and joggers relief from the linearity of the towpath. Part of my life has been dedicated to making interesting destinations along very long trails, whether in Durham, NC or in Princeton. With a hardwired devotion to things, I've been an advocate for this little nature trail, and the unique, savanna-like habitat it winds through, since it was created nearly 20 years ago. Periodically stopping by to check that the trail hasn't been blocked by fallen trees, reading the landscape as I go, I always come away with a mix of joy, gratitude, and grief. 

Some flowers encountered during this walk are native, like this red maple reaching out over the trail.

Then there are some non-native species that fortunately aren't invasive, and speak to past intention. These photos were taken a week ago, when the ornamental cherries were just starting to pop. 

These really old ornamental cherry trees are reminiscent of those planted along the Potomac River in Washington, D.C. long ago. The cherry trees and the yellow spray of forsythia off in the distance show that this seemingly wild stretch of the towpath is actually populated with botanical remnants of another era, back when the university installed these plantings as an ornamental entryway to the campus. 

Adding to the evidence of past caretaking is a derelict row of winter honeysuckle (Lonicera fragrantissima), with very small, very early, and very fragrant flowers. Though it's included on invasive species lists, I've never seen it spread. 

If you're an environmental advocate at a local level, a walk can become a review of past successes and failures. For years, the DR Canal State Park, of which this ribbon of land is a part, would keep this nature loop mowed, but then their maintenance budgets started getting cut. Around the time one of their longtime mowing crew members died, they decided to turn mowing over to the landowners--Princeton University. That handoff happened at an administrative level, but not on the ground. After trying in vain to get the university to take care of the trail loop, I finally contacted Shana Weber at the PU sustainability office. Thankfully, she was able to reach the right people, and the trail is now being kept open. 

But one bit of mowing that the state parks people used to do has yet to be picked up by the university. And here's where the landscape's story shifts from joy and gratitude to grief. The nature trail loop winds through what for many years has been a savanna-like landscape of scattered trees and fields. Scattered trees allow enough sunlight to reach the ground to power a rich understory of wildflowers and shrubs. But due to a lack of annual mowing, that special landscape of forest openings, seldom found elsewhere, is being lost. Here is a forest opening that has become a layer cake of invasive plants, with multiflora rose blanketed by a web of super-aggressive porcelainberry vine. 

Other invasive vines also run rampant, like this Japanese honeysuckle smothering a branch.

Why is no one cutting the oriental bittersweet at the base of this tree, the wild gardener in me asks.

Many of the trees were planted, then ultimately abandoned, leaving a kind of derelict arboretum.

Some trees have succumbed altogether to introduced insects or disease, most commonly Emerald ash borer or bacterial leaf scorch. 

On the ground, the uber-invasive lesser celandine is laying a claim that will surely expand. 

Without annual mowing to sustain the forest openings, a tortured form of succession is underway, with sweetgum saplings being mobbed by the invasive vines. Annual mowing would sustain the special forest openings and reduce the smothering invasives.

A couple places where the native species are doing well are, not surprisingly, in standing water. Here's a rosette of a very healthy rose mallow hibiscus (Hibiscus moscheutos), its feet very much in water.

Here's a shrub that also flourishes in standing water, buttonbush (Cephalanthus occidentalis). 

There are lots of native plants that can thrive in floodplain habitats along the canal. If the university ever gets interested in habitat restoration, this would be a great place to start. It would be a high-visibility demonstration, to be witnessed by all the hikers, bicyclists, and joggers passing by, who currently see not the history and the ecological drama but just another stretch of green.

Optimism, Habitat, and Landscape

If people love trees so much, then how do we explain Jill Biden's choice for a painting that was part of Inauguration Day ceremonies in the Capitol rotunda. Painted by African American artist Robert Duncanson as the Civil War was looming, Landscape With Rainbow depicts a pastoral paradise in which a young couple and their cattle head back to a homestead blessed by a rainbow. 

A closer look reveals that the distant hills in the painting are forested, but it is pasture--albeit a bit overgrazed--that dominates this optimistic landscape. Though people love trees, we also love vistas, which trees are very good at blocking. Who hasn't climbed a mountain, expecting a grand vista at the top, only to find that trees have grown to block the view? 

It seems strange sometimes that communities don't actively seek to create and preserve vistas, given how pleasing they are. If people can see into the distance, maybe they'll think into the distance as well. A vivid memory from the Sourland Mountains, just up the road from Princeton, is a view of the Manhattan skyline. It came as a complete surprise, and was made possible only by the ongoing suppression of trees along the gas pipeline right of way that extends up and over the mountain ridge. Ideally, vistas would be made possible in our world by something less linear and fossil fuel-related than a pipeline, but our approach to managing preserved open spaces seldom offers an alternative means of creating areas that are more open. 

Also running counter to open space preservation norms, the focus of optimism in the painting is a house, embraced by nature, towards which the rainbow, people and animals all point. One approach to purchasing open space for preservation is to demolish any buildings left on a newly preserved property. We had to overcome this bias against buildings embedded in open space in the process of saving Veblen House and Cottage at Herrontown Woods. 

One question, then, is how to adjust the classic view of open space--as uninterrupted forest--to consider the clear attraction we have for the mosaic of habitats depicted in this painting, where people play an active role in the landscape. What is pleasing to people can also serve the needs of biodiversity. At the Botanical Art Garden at Herrontown Woods, we are actively preventing a forest opening from reverting to the deep shade that stifles the growth of so many native plant species less gifted with height. Succession to forest need not be considered the only natural destiny for a landscape. Historically, such forest openings would have been maintained by periodic fire, in what is called a fire-climax community. 

Though a deep forest of towering native trees can evoke a sense of awe and reverence, and deserves to be preserved, many areas of preserved open space are thick with stunted, second-growth trees. Add the typically dense layer of invasive shrubs and the effect becomes cluttered and claustrophobic. As the death of ash trees due to the Emerald Ash Borer opens up the forest canopy, we may want to manage some of these openings to create a more varied habitat. If the non-native invasive shrubs can be limited, and young trees kept from reclaiming the sunlight, there are many native shrubs that could flourish in a more illuminated understory. Spicebush, hazelnut, serviceberry, native azalea, blueberries, Viburnums, Hearts-a-burstin'--these are a few of the native shrubs that would bear abundant fruit for wildlife if given more sun. 

One of the most optimistic moments I had in my life had some parallels to the Duncanson painting. I was driving out of Washington, DC after picking up a passport. The president at the time was highly competent and believed in government, and the WhiteHouse gleamed brilliant white in the afternoon sun as I drove past. On the radio was a live broadcast of Copeland's Appalachian Spring, broadcast from the Library of Congress in honor of its premier performance there some 50 years earlier. Along the roadsides as city began to transition to countryside were prairie grasses, golden in autumn. The youthful roadside vegetation resonated with the music of spring's awakening, and a sense of the nation's promise. 

Grasslands, meadows, shrublands--these are the younger landscapes, whose dynamic growth happens at our own height rather than far above. Their flowers and foliage also serve the insect community through the summer when deep forest has gone floristically silent. The aim here is to become more strategic and discerning about trees, to determine where they are precious, and where they might best be managed to serve ecological and aesthetic goals. 

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.