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. 

Evolved Coexistence in Nature

What is "natural" in nature? I remember a 1990 column entitled "Bug Wars," in which NY Times columnist Anna Quindlin wrote about the gypsy moths that, back then, were defoliating vast areas of eastern forest. She used the destructive moths as fodder for reflections on nature and its ways, not knowing that the moths can hardly be thought of as natural. They were introduced from another continent, then escaped and multiplied, consuming forests that had not evolved any defenses against them. Fortunately, scientists found a very low-toxicity way to limit the gypsy moth's numbers, though sustaining that balance requires ongoing human vigilance and action.

With introduced insects and diseases having decimated first our ashes and now our beech trees, it's worth noting the more sustainable relationships between plants and animals that have co-evolved over millennia on the same continent. 

Tent Caterpillars and Black Cherry

This spring, tent caterpillars defoliated some of our black cherry trees. Were the caterpillars a threat to the trees? Well, they finally got their fill and wandered off to pupate and become moths, leaving the trees to sprout new leaves and grow unhindered for the rest of the summer. The trees may grow more slowly, but their survival (and therefore the survival of the tent caterpillars that depend upon them) is not in peril. 

 

Hibiscus Sawfly and Rose Mallow Hibiscus

Near the gazebo in the Barden at Herrontown Woods grows the local native hibiscus (H. moscheutos). Earlier this summer, its leaves were getting eaten. 

Some internet research suggests that these are larvae of the hibiscus sawfly. 

If the culprit had been an introduced insect, I might have worried. For instance, each year I see more evidence of our arrowwood Viburnums being eaten by the Viburnum leaf beetle, an insect introduced from Europe. Because the beetle's arrival is fairly recent, we don't know if it poses an existential threat to Viburnums.

But given that the native hibiscus sawfly has been interacting with the native hibiscus for thousands of years, that long track record of coexistence is reassuring.

 

Though many leaves were partially eaten, the hibiscus grew new ones that remained unaffected. I think of this relationship as akin to someone who donates a percentage of their income to good causes each year. 

An Aphid-like Insect and Hickory Trees

Earlier this year, some leaves of a young hickory tree developed these green bumps. They appear to be hickory leaf galls, caused by an aphid-like insect in the genus Phylloxera. 

The hickory leaves ultimately curled up. The insect's lifecycle sounds much like that of the introduced nematode that causes beech leaf disease. Should we be worried for the future of hickories?

Again, the aphid-like Phylloxera and the hickory tree "go way back," and through those millennia a balance seems to have been struck. Only the lower portions of the tree appear affected. The hickory continues to grow. 

Psyllids and Persimmon

Lastly, a twig on a native persimmon in Herrontown Woods was showing symptoms of contorted leaves similar to those proliferating on nearby beeches. Might we be losing our persimmons? Again, some internet research points not at apocalypse but at coexistence, between the native persimmon and a native insect called the persimmon psyllid. 

According to a NC State website,

"On native persimmon, these psyllids can be temporarily abundant; but their populations soon decline naturally, as they are attacked by their natural enemies, including parasitic wasps."

For some, even small blemishes on a plant will be annoying, but in a nature preserve, the long-sustained give and take between the plant and animal worlds is part of a complex food web to be celebrated. 

We could wish that the beech and the introduced nematode that threatens it would ultimately come into a balance that allows coexistence, but other native tree species laid low--chestnut, elm, ash--remain marginalized, even, as in the case of the American chestnut, more than a century later.

Campus Grounds Sprout Local Flora

Some areas of Princeton University's intensely landscaped campus are starting to sprout local native flora. Using native plants doesn't necessarily mean those species will be found in local nature preserves. Many native plants popular in landscaping--purple coneflower, red buckeye, bottlebrush buckeye, oak-leaved hydrangia, witch-alder, Virginia sweetspire--are seldom or never seen growing on their own in the local wild. 

But recently, the University has been planting the actual species frequently encountered in local nature preserves like Herrontown Woods and Mountain Lakes. This spicebush shrub in front of the Lewis Center for the Arts, 185 Nassau Street, resonates with the spicebush  so common in our woodlands.  

 

Turf has been replaced with a sedge meadow, probably the same Pennsylvania sedge that can be encountered in remnant meadows in local woods.

Masses of Christmas fern now grow on campus as they do along the slopes of the Princeton ridge.

A few species, like the foamflower making this mass of white, are rare to nonexistent in local woodlands, but the overall trend seems to be to treasure what is authentically local. 

Though some of the University's early efforts to plant native landscapes became overrun with weeds, this 2-3 year old planting down near Robert's Stadium is thriving. Better soil prep and thick mulch (and more knowledgeable gardeners?) have, at least thus far, conquered the weeds. The native species chosen are again those one finds in the local wild: cutleaf coneflower, arrowwood Viburnum, and wild rye grass. 

People naturally want to plant things that are special, and special used to be defined by distance--as in exotic plants imported from distant continents. Distance made the botanical heart grow fonder. It's heartening to see a shift in what is viewed as special, towards a valuing of what is truly local.  

Helping Herrontown's Beauty Express Itself

There's a lot of built-in beauty at Herrontown Woods. Rocks, wood, and water serve as the basic infrastructure upon which other beauties are overlaid. 

This time of year, it's the understory that gets to shine, just before the tree canopy envelopes the woods in shade. Much of the habitat restoration work we do at Herrontown Woods involves bringing back the beauty and functionality of the native flora. By removing nonnative invasive shrubs that clog the understory, we open up vistas and release the existing native flora from stifling competition. In a sense, we are filling in for the deer, which chow down on native shrubs while leaving the nonnative shrubs uneaten.

Walk up the new boardwalk from the main parking lot to witness a corridor brightened by flowering dogwoods, 

and hundreds of blackhaw Viburnum shrubs adding clusters of white flowers extending deep into the forest.

Redbuds can't survive in the deep shade of the forest, but they proliferate on the more open Veblen House grounds.

This year, we spotted two wild azaleas blooming along Herrontown Road. Fifty years ago, it would have sounded strange to be excited about a couple wild azaleas in the preserve. They were numerous back then, but have been literally laid low by increasing deer numbers and deepening shade. 

It's taken more than a decade of ramblings in the preserve to realize that some kinds of native shrubs we thought long gone in fact remain numerous on the forest floor in miniaturized form, browsed before they can grow sufficiently to bloom. The town's deer culling program has helped native shrubs like spicebush to rebound, but for some species, additional effort is needed.

Protected by cages and given some sun, pinxter azaleas, serviceberries, and hearts-a-bustin' are making a comeback in the Botanical Art Garden (Barden) next to the main parking lot. New plantings of native buttonbush, silky dogwood, pussy willow and elderberry are also being protected until they can grow and flower beyond the deer's reach.

In these ways, we help another layer of beauty in Herrontown Woods to express itself.

PHS Ecolab Wetland Update -- Early June

The Princeton High School Ecolab wetland continues to bounce back nicely from its surprise defoliation last fall. 

If you pass by, you'll see the cattails that we're hoping to keep contained in one corner. The cloud of gray-green beyond is an annual grass planted by contractors as a cover crop, dotted with the deeper green of all the pre-existing native plants now re-emerging from their roots.

The ponds have water, despite the extended drought--sign that the sump pumps are now functioning again, delivering water from the school's basement up into the wetland. 

If you look a little closer, you may see some native blue-flag irises still blooming, happy as clams in this wet world.

On drier ground, the common milkweed is about to bloom.

Bindweed, in the morning glory family, is advertising its location. It's a non-native vine that is too aggressive. While I went around pulling it out (if we could use herbicide, we could kill its roots and be freed of an ongoing task), I checked to see what other plants are rebounding. 

Joe Pye Weed is back, as is fringed sedge.

Good to see boneset and Hibiscus popping up. They don't look like much now, but a (wild) gardener can see the promise in these little nubbins.

It can be a challenge to distinguish a blackhaw viburnum sprout from

silky dogwood. Both of these, along with elderberries, will grow back from their roots to become big shrubs. Since trees become oversized for the site, these shrubs will have to do as places for birds to land and hide. Large shrubs will also help curb the expansionist tendencies of cattails. 

We'll see how the lack of shade, now that trees have been removed, will affect the balance of the various species. Some plants like cattails and lizard's tail may spread more aggressively now that they are in full sun. But overall, the rebound is looking good.

Documenting the PHS Ecolab's Recovery From Last Year's Trauma

Passerby on Walnut Street may have noticed that the Princeton High School Ecolab wetland was completely stripped of vegetation by an outside contractor this past November. After the shock of having so many native shrubs and wildflowers suddenly gone, it took us awhile to realize that the roots of the native plants might still be alive beneath the bare dirt. Having lobbied successfully to have stewardship of the Ecolab returned to the teachers, students, and volunteers who had cared for it free of charge for fifteen years, we are watching for signs of its rebirth. 

Most obvious is the annual grass planted by the contractor for erosion control. But I took a closer look and found gratifying evidence that the wetland will rebound. Click on "Read more" below to see a photo inventory of 40 native species (and a few very manageable weeds) that have popped up thus far, ready to refoliate this wonderful teaching resource for the school's environmental science program.

What Privet is This? Border Privet in Princeton

A botanist friend of mine, John L. Clark, asked one day if I knew which kind of privet we have here in central New Jersey. John's extremely knowledgeable about flora of farflung places like Equador, but he has some charming gaps in knowledge of local flora that I can sometimes help with. Though I knew there were different kinds of privet--European, Chinese, Japanese--I had long been content to just call any thick infestation of the shrub by the general name of privet, and think no further. All the species of privet are nonnative and invasive, so for management purposes, it's not necessary to know one kind from another. 

More important for management is to be able to distinguish the non-native privet from native shrubs with similar appearance, particularly the native blackhaw Viburnum. Both have opposite branching, but privet often has a terminal cluster of small black berries that linger through the winter. And many of the privet leaves linger through winter as well. 

The photo shows the difference in the shape of the buds. The longer bud on the top (curved here, but sometimes straight) is blackhaw Viburnum. The stubby, grayish buds on the twig below are privet. 

Sometimes privet's winter leaves can take on various shades of green, sometimes bordering on purple or brown. 

I was glad John persisted in his quest to find out which privet we have in central NJ. Having lived in the south, he at first assumed we have Chinese privet (Ligustrum sinense), but after posting a closeup of the flower on iNaturalist, he soon learned that we have Ligustrum obtusifolium, latin for border privet.

Posting another closeup, John pointed out various identifying characters of border privet: "Corolla tubular with small lobes (the tube longer than the lobes), Shoots pubescent (i.e., NOT glabrous)"

The Penn State post describes "a gradient of four different species: border (L. obtusifolium), common (L. vulgare), Japanese (L. japonicum), and Chinese (L. sinense)." But John has determined that we only have border privet here, probably because it is the most cold-hardy. When I lived in North Carolina, we had a mix of Japanese and Chinese, with the Japanese having much larger and glossier leaves. 

Thanks to Inge Regan and John Clark for these photos. Winter, by the way, is a great time to go after infestations of privet in the backyard or local woodlands. Come by Herrontown Woods on Sunday mornings after 10:30am and you'll likely see the Invasive Species of the Month Club clearing swaths of privet to make room for native species.

Strangler Figs: Airborne Roots and Flying Buttresses

Coconut Grove, FL, where I was fortunate to spend a week with family for the holidays, is named after its palm trees, but the tree that will catch your eye more than any other is the strangler fig. 

How silly we are, these extraordinary trees seem to say, to think that trees should start life on the ground, have only one trunk, make their flowers seen and keep their roots tidily hidden. 

The strangler fig's logic is clever. How can a new tree survive in a tropical forest where existing trees cast deep shade and have a lock on soil nutrients? It starts its life as if on stilts, as an epiphyte high in the canopy, sprouting on the trunk of another tree. Oftentimes, the seeds, freshly digested by a bird, catch in the rough bark of a live oak, or a cabbage palm. Declaring itself improbably independent of nutrition from mother earth, it lives at first on air and rain, growing stems skyward and roots earthwards. When the roots reach the ground, the strangler fig's growth accelerates. The above ground portions turn into multiple trunks that envelope the host tree. That embrace can ultimately prove lethal, providing the strangler fig with a convenient supply of additional nutrients as the host tree rots away. 

 

More and more roots are sent downward, each one turning into yet another trunk when the roots reach the ground. Surely if one trunk is good, then many must be much better. The result brings to mind a cathedral replete with flying buttresses. 

The result of all this free-thinking, or if not thinking, then free-doing, is a tree you can walk through. 

This old beech tree in the Institute Woods in Princeton achieves a somewhat similar effect, though it's just one trunk that has rotted through. A closer equivalent in our forests is achieved in a more covert fashion. Trees like beech, sassafras, pawpaw, black locust, aspen, and the blackhaw Viburnum sprout new trunks as their roots spread underground, creating what appears to be a grove of trees that is in fact one individual.

Wikipedia lists 13 different species of strangler fig around the world. This one at Barnacle Historic State Park is the native Ficus aurea, whose fruits the sign says are edible. 

I'm guessing that many of the other strangler figs--those with myriad trunks like this impressive specimen at the University of Miami--are banyan trees from India.

On the left in this photo you can see some aerial roots growing towards the ground. 

Here's a closeup of a cluster of soil-seeking roots growing downward from a limb--another tree trunk in the making.

What little bamboo I saw in Coconut Grove paled in comparison to the expansionist aims of strangler figs. 

This fig appears ready to eat the pavement, 

while others drape themselves over walls, 

or probe the local infrastructure.

This strangler fig was so bold as to break into a tiger's cage.

Fortunately, there's no tiger living there now, just a couple of chickens. 

I forgot to mention the hidden flowers, which are borne inside the fruit and accessed only by a tiny wasp. Each species of fig has its own specialized species of fig wasp to fertilize it. For more reading, and some cool photos of just how tiny those wasps are, here's an interesting post. This Forest Service post describes the mutualistic relationship between the wasp and the tree, and says the U.S. has only two species of native fig. 

For anyone headed down Florida way, a good example of a banyan tree can be found at the Marjory Stoneman Douglas Minipark, named after the famed activist and author of The Everglades: River of Grass.