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.  

What's Eating Local Viburnums?

Each time I see a native arrowwood Viburnum growing in the woods, I take a closer look. There's a viburnum leaf beetle--a nonnative species introduced from Europe--that showed up in Princeton about a decade ago. On a visit to Pittsburgh years back, I saw native Viburnums totally skeletonized by the insect, and worried about the fate of our own Viburnums in NJ. 

I've posted about this insect pest in the past. Suffice it here to say that among the various species of Viburnum in NJ, the arrowwood Viburnum (V. dentatum) is the most vulnerable. The nightmare scenario would be for the leaf beetle to defoliate all arrowwood Viburnums, then move on to decimate the next most vulnerable species.

Preferring wet ground, blooming profusely even in the shade, the Viburnum dentatum is not as common in the woods as the blackhaw Viburnum, or the highly invasive Linden Viburnum. The last couple years, I didn't notice much insect damage. This year, observations are mixed. Some shrubs in Herrontown Woods were badly eaten, 

while an arrowwood across town in Rogers Refuge showed no damage at all. 

Hopefully, the total stripping of leaves that I witnessed in Pittsburgh will prove to have been an exception, and natural predators and diseases will keep the Viburnum leaf beetle in check. Worth keeping an eye on in coming years.

The Emerald Ash Borer Quietly Changes Princeton's Skyline

Scan any skyline in Princeton and you're likely to see dieback in the trees. This happens to be the view from the front step of Veblen House in Herrontown Woods, but the same can be seen in the woods surrounding Princeton Battlefield, and most everywhere else in town. 

We're losing thousands of trees in Princeton, some quickly, some slowly. As described in past writings on this blog, dating back to 2010, the Emerald Ash Borer is proving every bit as destructive as predicted, killing all species of ash tree. And many red and pin oaks are succumbing to an introduced disease called bacterial leaf scorch. 

Many of the trees lost to introduced insects and pathogens in the past century or so--first the American chestnut, then the American elm, and now the ashes--had been dominant trees in our forests. Until the Emerald Ash Borer arrived, sweeping east from its point of introduction (hitchhiking in packing crates from Asia) in southeastern Michigan, the ash had been Princeton's most common tree. The physical gaps, if not the ecological ones, get filled by one thing or another. At Herrontown Woods, tulip trees, red maples, hickories, and sweetgums grow into the voids. 

These radical changes in the forest canopy present challenges for those of us who manage Princeton's woodlands. Dead ash trees become brittle over time. Branches and sometimes whole trees fall across trails, requiring removal. Though the town arborist and his crew have been helping, oftentimes it's volunteers who carry chainsaws deep into the preserves to reopen a trail. 

At Rogers Refuge, Princeton's birding mecca just downhill from the Institute Woods, it is avid birders who work on the trails. Lee and Melinda Varian have been particularly active. Melinda recently sent an email to the Friends of Rogers Refuge group, of which I'm a part, to report that "Lee and I just went out with our chainsaws for the third time this week to
clear fallen Ash trees from the Red Trail. It’s really heartbreaking."

She sent us these photos of a 50 year old ash tree that had fallen across a trail. Another volunteer at Rogers Refuge, Winifred Spar, wrote about how the history of the refuge is embedded in each tree's growth rings.  

In this section of trunk, where the bark has fallen away, you can see how the Emerald Ash Borer larvae consume the tree's cambium. Like the earth's total dependence on a thin surrounding layer of atmosphere (which of course our machines' invisible emissions are radically altering), a tree's vascular system depends on a thin layer of tissue surrounding the trunk, just below the bark. Lacking any evolved defense against the introduced ash borers, the native ash trees quickly become girdled and die. 

Though other tree species like oak and elm may be considered more statuesque, I have been surprised on occasion by just how gloriously big an ash can become. Two examples stood along the oval drive leading to George Washington's home at Mount Vernon. Another stood at the top of the bank of the Delaware in Lambertville. I was in awe at the thickness of their trunks. Surely the one in Lambertville has been lost, but might those at Mt. Vernon have been saved through chemical injections?

As tens of thousands of ash trees die in Princeton, requiring a vast expenditure to remove, has anyone actually seen an Emerald Ash Borer? I have seen a grand total of one, and that was a decade ago in Ann Arbor, MI, close to where they first were discovered in the U.S. By contrast, everyone has seen, and squashed, a Spotted Lanternfly, yet compare the harm done by the these two introduced insects and it's clear the largely unseen ash borer has been far more devastating in its impact. Our senses largely fail us for discerning the greatest threats to our world, be they an elusive insect or, far more devastating still, too much carbon dioxide in the atmosphere. To coin a phrase, call it "quiet radicalism."

By allowing light to reach the understory, the gaps in the canopy created by so many dying trees present a mix of problems and opportunity for managing our preserves. What shrubs will take advantage of the extra solar power, previously harvested by the trees but now reaching the forest understory? Native understory species like blackhaw Viburnum, highbush blueberry, and spicebush can now flourish and produce more fruit. If the deer didn't eat them, rarer native species like shadbush, pinxter azalea, and hearts 'a bustin' could make a comeback. But oftentimes, it is nonnative invasive shrubs that have colonized our woodlands--Photinia, honeysuckle, linden viburnum, winged euonymus, multiflora rose, and privet. Left uneaten by wildlife, the nonnative shrubs have a competitive advantage that could render our woodlands clogged with foliage inedible for local herbivores. 

Changes in the understory can affect whether wildlife thrive. Winifred, a keen observer of bird life in Princeton, wonders "if the gaps in the canopy and increased invasive understory may already be having an effect on birds in the Institute Woods. It might explain why there were noticeably fewer Ovenbirds this past summer; they are ground nesters." 

The ash tree won't disappear altogether. One old post, from 2014, entitled After Emerald Ash Borer, What Will Princeton Look Like, describes a visit to Ann Arbor, where the ash borer had already swept through. We still found young ash trees. My best guess back then remains my best guess now:

I would speculate that, once the native and introduced parasitic wasps become widespread, they in combination with woodpeckers could allow ash trees to persist in Princeton, though perhaps few would grow to maturity unless regularly treated with systemic pesticide.

Carolyn Edelman, a poet and nature enthusiast, recently posted a quote of Adlai Stevenson, II, dating back to a speech he gave in 1952. Its sentiment is part of a vein of American thought that views love of the American landscape as deeply connected to the love of freedom. For me, it is not coincidence that we live in a time when both nature and democracy are being undermined.  Read the quote through today's filter of gender equality and inclusion to find its relevance.

It was always accounted a virtue in a man to love his country. With us it is now something more than a virtue. It is a necessity. When an American says that he loves his country, he means not only that he loves the New England hills, the prairies glistening in the sun, the wide and rising plains, the great mountains, and the sea. He means that he loves an inner air, an inner light in which freedom lives and in which a man can draw the breath of self-respect. Men who have offered their lives for their country know that patriotism is not the fear of something; it is the love of something.

A great tree species passes from the landscape, but the love remains, and in that love reside both grief and possibilities.

September Nature Vignettes

 Encounters with nature and sustainability around Princeton in September.

One of my favorite corners in Princeton is near the middle school, at Guyot and Ewing. It's a small enclave, a triangle of sense, where the yards and the roofs of houses actually perform work, growing food and gathering energy. On one side is a small house with a small yard that the owner has turned into an orchard and vineyard, as might be more often encountered in Italy. 

Nearby is a house whose south-facing roof has been completely covered with solar panels for 20 years. 

When a house was torn down recently at the corner, I feared it would be replaced with something huge and unattractive, 

but instead, a one-story house with extra thick insulated walls and solar panels and interesting design is taking form. It was a real surprise to see a one-story house being replaced with another one-story house that is sensitive to the history of the site and seeking to fit in, while showing off a modern design that seeks to minimize energy consumption.

They even have a sign on the fence describing the project and what was there back in Princeton's agrarian era. 

Blooming along the fenceline next to the house are sunflowers and autumn clematis vine. Gorgeous as they are, thankfully generating color at a time when most flowers are spent, they are best not planted in a garden unless where the spread of their roots is limited by a house or pavement. Otherwise, given abundant sun to power their aggressively spreading roots, they will take over your garden.

Another common encounter in September is with late-flowering thoroughwort, which spreads not by roots but by seed. It can be weedy but also lovely and even elegant at times, and is great for pollinators. I couldn't get myself to pull this one out in our backyard, even though it has completely taken over a garden path.

At the Barden in Herrontown Woods, they are so plentiful that we don't feel too bad pulling out the ones that lean over the pathways.

The fight against invasive species has the side benefit of taking me to areas of a nature preserve where I wouldn't otherwise go. Recently, it led me to a patch of native diversity in Herrotown Woods that I hadn't noticed before.

Here is obedient plant, 

New York ironweed, 

and the post-flowering look of water hemlock. 

One of my favorite garden plants this time of year is stonecrop "Autumn Joy." 

A sedum, its disks of flowers go through a gradual enrichment of color from green to pink to deepening shades of red, then finally chocolate. Nonnative but noninvasive, it has the added benefit of being popular with pollinators. 

Pawpaw trees are becoming more common in Princeton. The patches planted in Herrontown Woods have yet to bear, but this one in my backyard reflects a growing interest in this unusual species native to the north yet with a tropical taste.

Native persimmons, likely once common in Princeton but often shaded out by larger trees in recent decades, are an attractive smaller tree that might actually bear edible fruit if you happen to get a female and harvest it just at the right time.

If the drought hasn't made the berries too dry, these blackhaw berries could make for some good picking after they darken. Blackhaw viburnum, Viburnum prunifolium, is the most common native viburnum in our woodlands.

Less generating of anticipation are the fruits of a female ginkgo tree, encountered growing near the Princeton Junction train station. The fruits have such an unappealing smell that people try to avoid planting female trees. 

Among inedible fruits, I call this the incredible shrinking pokeweed, because it initially grew to be seven feet tall--way too big to grow along a busy street. So I cut it down midsummer and thought that was that, only to have it sprout back as a smaller version of itself. You could try this technique with a number of perennial native wildflowers that get too tall for people's taste. Cut them down partway through the summer, then let them grow back in a miniature form. 

Though it dies down to the ground each year like a perennial wildflower, pokeweed looks more like a miniature tree, and in fact it has a close relative in Argentina. The ombu grows to the size of a large tree, yet lacks xylem. 

This shrub, too, needs to be cut back. It's an oak-leafed hydrangea I planted long ago in a little raingarden at the front of the Whole Earth Center. The landlord the store leases from must have a new landscape firm taking care of the grounds, because I stopped by recently to find that my native shrubs have been trimmed to look like bowling balls. Funny to see a native shrub and wildflower planting getting the bowling ball treatment. I'll have to take some loppers to restore light to the window next time I stop by to buy some beets or delicious bread.

Sometimes, frequently in fact, I find myself wishing I wasn't right. Take this ash tree for instance, planted by the people who landscaped the new parking lot that Westminster Choir College built about ten years ago. I told them they needed to remove the ash trees they had just planted. The emerald ash borers are coming, and the trees won't survive. They left the trees in. The trees survived longer than I expected, but are finally succumbing. 

Actually, if you were trying to make Princeton sustainable, you might want to "farm" Princeton with smaller, short-lived trees that provide shade but are less expensive to take down. The above ground portions could be periodically harvested as a local energy source, and the roots left in the ground would sequester carbon. Trees are a source of solar energy, since they draw their carbon not from underground but from the atmosphere all around them. Thus, no net increase in atmospheric carbon from their combustion.

The landscaping for the parking lot also called for a raingarden to be planted here in this hollow. After being planted, the young river birch trees soon began to wither for lack of water. I assumed they would die, and that the raingarden would be poorly maintained and ultimately be mowed down. I was only half right. The river birch trees survived.

Here's what looks like a bright white flower that isn't. The white is the puffy seeds that give the plant its name. The flower seems not to open but remain in what looks like a bud stage. It's pilewort, a native weed that can reach seven feet tall.

Finally, a grass encountered in fields and local rights of way. When its flowers open and display their golden anthers, this native member of the tallgrass prairies can be eye-catching. Indian grass, Sorghastrum nutans, reminds me of the midwest prairies I used to help manage, and a time long ago when prairie openings were common in the east as well.