After Emerald Ash Borer, What Will Princeton Look Like?

Back in July, I took a trip to the future. Princeton still has a few years before the emerald ash borer is expected to decimate our ash trees (what a cheery sentence that is), but Ann Arbor, MI, has already weathered the EAB storm. The city is located less than an hour away from the original introduction of the insect, which went unnoticed in the Detroit area from the early 90s through to 2002 when it was finally identified. The introduction was likely via wooden shipping crates arriving in Detroit/Windsor from China.

Ann Arbor's tree removal lasted ten years and cost $5.8 million. What does this city of 110,000 look like now?

By chance, my trip to Ann Arbor coincided with a visit by college friend and early EAB researcher Dave Cappaert. We visited County Farm Park, one of the sites where he and fellow entomologists did the dirty work of cutting open some 10,000 ash trees to study the behavior of the emerald ash borer and search for parasites that might help control its numbers.

While immersed in research on EAB, Dave discovered a formerly unknown braconid wasp that parasitizes EAB larvae, and now bears his name: Atanycolus cappaerti. Other useful parasites have also been discovered, here and in China, and they could play a role in reducing the number of emerald ash borers that continue to affect ash trees after the first mega-wave of ash borers passes through an area. There's a video that gives a brief history of EAB (complete with darkly evocative sound effects) and then describes three parasites of EAB that were found in China and are now being released in the U.S. after thorough testing.

There's a bit of good news. Valued ash trees along streets or in yards can be spared, for a price. And wild ash trees do not disappear altogether. We found 20 foot tall ash trees making a go of it, here and there. Dave says that 80% of the EAB larvae get eaten by woodpeckers. It's still a mystery how the woodpeckers are able to locate the larvae under the bark with such consistent precision.

Here's a young ash showing the outer symptoms of EAB attack. 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.

While we were walking around, Dave found one of the signs he and other researchers had placed around the park years back to explain why they happened to be pulling the bark off of thousands of trees in a public park.

Click on the photo to make it more readable.

Here's an ash tree showing signs of dieback on the upper right--likely to be a common sight in Princeton in coming years.

HOW TO SAVE SPECIMEN ASH TREES

It's important for those who have ash trees in their yards to know that those trees can be protected with systemic pesticides. Not all the available pesticides are equally effective, however. Though imidicloprid is being frequently recommended locally, the experts in other states that I've spoken to have all recommended emamectin benzoate (brand name Tree-Age, or Arbor-Mectin).

Page 15 of this document is very informative, and says the emamectin is the most effective and longer lasting, while warning against use of imidicloprid on larger trees. Dave says that the EAB expert Deborah McCullough recommends emamectin, which is supported by this article about communities in Minnesota. The article is very optimistic about saving some ash trees, and offers this interesting approach:

"Burnsville is so sold on that idea of saving trees, rather than cutting them down, that it plans to encourage residents to treat their trees by extending to them the rates the city receives for pesticide injection. "

Curtis Helm, a former Princetonian and currently an urban forester in Philadelphia's Parks and Rec department, advises against using imidicloprid on trees larger than 16" diameter. He says Philadelphia is treating 1000 ash with Tree-Age.

In a previous post on the subject, I included notes from an extended conversation with Donald A. Eggen, Division Chief of Forest Pest Management Division of Pennsylvania. He, too, strongly recommended Tree-Age rather than products that use imidicloprid.

The emamectin benzoate, last time I checked, was more expensive, which may explain the local preference for imidicloprid, but that cost differential is reduced when the frequency of application is considered.
Note: The Arbor-Mectin formulation is said to be absorbed into the tree more quickly than Tree-age, and therefore can be less expensive to apply. Both use the same active ingredient.

Any decision about how Princeton should proceed with pesticide applications (some homeowners have already begun applications, given that EAB has been discovered 25 miles north of here), should weigh heavily the input of those in Michigan, Pennsylvania and elsewhere who have benefited from years of experience.

Sailing and Seaside Solidago

Sailing is a lot like gardening in that it teaches one to work with nature rather than against it. Yesterday, I helped a friend get his most-amazing sailboat ready for the winter. I say most-amazing because I had not before been on a sailboat that's been around the world three times. My previous notion of a great sailing adventure came from camp counseling days when I took some high school kids from Camp Innisfree, near Sleeping Bear Sand Dunes, out to Lake Michigan's South Manitou Island in a daysailer. 

This boat, called Makulu, which in an African language means "big happy Momma", is equipped to nurture far greater ambitions.

For the time being, though, it will spend the winter with all the others, parked on stilts.

Among the emotional struts keeping my love of sailing well supported and ready to launch at any moment through all these non-sailing years is surely that feeling of acceleration experienced many decades ago when a strong breeze hits the sails. There's the sheer elegance and gracefulness of sailing, the economy of well-trimmed sails, the great good luck--a sort of alchemy--of being propelled forward with no effort beyond keeping a good grip on the rope and tweaking the rudder. Sailing permanently associates the elements of sustainability--renewable energy, efficiency, reuse--with pleasure. Experiencing how something invisible can power travel is also good training for understanding how carbon dioxide could be so transformative.

While big happy Momma was getting a good powerwashing to knock off the accumulated barnacles and algae, I decided to do some seaside botanizing. A jumble of concrete may not look like the most promising spot to explore, but it yielded some beauty and meaning.

First seen was an encounter between two grasses. The smaller one I'll say is smooth cordgrass (Spartina alterniflora), with the proviso that my coastal botany chops haven't been refreshed since the days of reading Rachel Carson's descriptions of two species of Spartina in the salt marshes decades back. In the background, taller and with pompoms for seedheads, is Phragmitis. It's a pretty picture, but there's drama beneath the tranquility.

Phragmitis is both beautiful and a botanical bully. In a freshwater wetland, it is the uber-invasive exotic, able to overwhelm even the aggressive native cattail. Here, the peaceful scene shows nothing of the underground battle being waged, as the Phragmitis' rhizomes invade the cordgrass' territory, ready to outcompete, overshadow, and ultimately displace. Meanwhile, the smooth cordgrass, loved as an integral part of the coastal ecosystems of the eastern seaboard, is proving detrimental and bully-like where it has been introduced into the differently evolved marshes of the west coast. As they say in real estate: location, location.

Here, the cordgrass plays off the sailboat masts in the distance.

One tough beauty blooming in the rubble is Seaside Goldenrod, Solidago sempervirens.

Bees were showing appreciation.

(Time out here to take a swipe at that most durable of botanical falsehoods, which thrives even in the minds of many nature lovers--that being the stubborn belief that goldenrod is allergenic. No. Ragweed, an unassuming wind-pollinated plant that blooms at the same time, is the one that produces the symptoms people falsely associate with goldenrod. How that falsehood has been able to thrive without periodic smear campaigns should be a topic of political science research.)

Here's an evening primrose growing up through Japanese knotweed.

The knotweed, whose invasive tendencies seem muted by the salty environment, grows next to a big clump of native indigo bush (Amorpha fruticosa), a legume whose acacia-like, bluegreen foliage can provide an appealing contrast in a backyard garden.

All this mixed talk of beauty and invasiveness is really about balance, which sailing teaches as well. Give us wind, but not too much or too little. Nearly two years ago, this sailboat and all the others at this marina got a big gulp of too much wind, when Hurricane Sandy rolled in, piled boats as if they were toys, and sank this sailboat in the harbor. To salvage the mast if nothing else, it was deemed worth pulling up out of the muck.

The plants, I'm sure, dusted themselves off and went back about their business of growing.

Death of a Stream

During my visit to North Carolina last month, my friend Perry took me to see how erosion can destroy a creek. Just last year, there had been a healthy, shallow, narrow creek meandering through this section of a wooded valley. What we found on this visit was a ditch eight feet deep. Trees had fallen as erosion undermined their roots, the ground pulled out from under them. This land is protected--preserved for all time--and yet the stream appears to be self-destructing within the boundaries of this nature preserve.

How this happens is completely counterintuitive. There's no rogue backhoe tearing at the tree roots, no misguided government policy like the channelizations of streams that happened in the 1960s. Though we usually think of erosion as being a process that degrades a stream from the top downward, this demolition starts downstream and heads up. Furthermore, the valley upstream of this section is undeveloped beyond a few scattered homes.

The process at work can be seen in the lower left of this photo, where there appears to be a ledge, a sudden dropoff in the mud. That's what's called a "head cut". As water flows over that ledge, it erodes the face of the dropoff, causing the ledge to gradually shift upstream. The same process is at work on a much grander scale at Niagara Falls, which is slowly but steadily moving upstream from where it was millenia ago. It's like the streambed were a loaf of bread that someone has been cutting slices off of, slice after slice, heading upstream.

How did this process of destruction get started? On the map, there are two branches of a stream that flows northward (bottom to top on the map). At the lower right is I-85. Tens of thousands of people drive peacefully by every day, their ride made smooth and safe by that broad ribbon of carefully engineered concrete. Not one of them is aware that the road, a ribbon of impervious surface, sheds copious amounts of stormwater, which then barrels down the creek, creating enormous erosive pressure. Somewhere miles downstream, the bottom of the creek gives way. A headcut begins, which then "travels" upstream, back towards the source of the eroding stormwater, consuming and deepening the creekbed as it goes.

Though the little branch of the creek on the left of the map, the one we visited, isn't downstream of the freeway, the erosion of the main branch created a headcut that then headed up the smaller branch as well.

We looked at the soil. It was sandy rather than piedmont clay. At this point, Perry pointed out that the headcut was moving upstream so fast--we estimated 200 feet of creek consumed by erosion in the past year alone--because the soil it was cutting through had not been there a few hundred years ago. During the heyday of tobacco farming, the soil that washed off the fields accumulated in the valleys. The stream is actually cutting down through layers of silt deposited during the agricultural era.

This might suggest that the erosion is actually helping the creek return to its historical level, but the result will not be restoration. Even though the creek may end up down near its original level, the valley's vegetation is still perched high on all the silt. The creek has become disconnected from its floodplain. The water table in the valley drops to match the level of the creek, which makes the vegetation more susceptible to drought.

A healthy creek floods easily and often, in the process dissipating energy and watering the surrounding floodplain vegetation. A deeply incised creek floods rarely, so that all that weight and power of water puts erosive pressure on the creek banks, detaching the stream even further from its natural interaction with the floodplain. Aquatic life has a hard time of it when its home is being either eroded away or buried in silt.

Christmas ferns and witchhazel will still grow on the slopes of the valley. But the valley is changed. The headcut has reached a spot where a beaver dam had created a wetland. Chances are, the headcut will undermine the dam and drain the wetland. Yet another example in our world of how cause--the building of an interstate a half century prior--can be so distant in time and space from ultimate effect.

Humanities and Environment Series Starts Today

The Princeton Environmental Institute is sponsoring a series of panels on "how we can deploy the essential insights and methods of the humanities and arts to tackle urgent environmental issues."

The first panel, today at 4:30 in McCosh 10, will feature prominent environmental historian William Cronon, who gave a masterful talk last night that traced the concept of wilderness from the Bible and 17th century America through to its relevance today as we enter the Anthropocene.

A Piedmont Prairie Selfie

Even prairies are taking selfies. What a great looking group. All smiles. They were all decked out, celebrating this special event called "late summer". These plants live in Durham, NC, which is part of the same piedmont as Princeton. Some, like Indian grass, black-eyed Susan, and probably wingstem as well, are found in NJ. One of my favorite native grasses, split-beard bluestem, and something called purple disk sunflower, which isn't included here because it was too busy making seed to join the photo op, show NJ as the northern edge of their range. Another plant that, despite hanging out in seedy places like empty lots, can be a real beauty, is hyssopleaf thoroughwort--a smaller version of a plant common to our area, late-flowering thoroughwort ("late boneset" for short). Like the golden aster in the lower left (Chrysopsis mariana), the hyssopleaf thoroughwort appears to range even further north than NJ, but doesn't show up around Princeton.

Grasses are hard to photograph, but you can see how these fuzzy seeds of split-beard bluestem split off in two directions. Backlit, a patch of this grass has a cottony glow. In Princeton's meadows and along right of ways, we have little bluestem, broomsedge bluestem, and a few scattered specimens of big bluestem, none of which have this ornamental clustering of seeds but which can still be easily identified by their overall appearance.

Also at the site were a blue lobelia,

and Meadowbeauty (Rhexia mariana).

That all these species, plus post oaks, can be found here suggests that this preserved land holds promise for restoration as a piedmont prairie or post oak savanna.

Remembering to Celebrate

On a recent trip down the piedmont to Durham, NC, I was handing out congratulations left and right. For starters, there was the fifteenth birthday of the nonprofit I started there in the pre-Princeton years.

While in town, I also congratulated this corn on having grown up to the roof of a two story house bordering one of the urban nature preserves. Giant corn is associated with Jala, Mexico, near Guadalajara, which is towards the Pacific Ocean from Mexico City. Grow enough of this tree wannabe, and you might be able to shade your house in late summer.

There was the incredible shrinking lawn of my friend's neighbor, who each year de-turfs more of his front yard and replaces the lawn with tomatoes, herbs and watermelon.

I congratulated this "rabid wolf spider" (Rabidosa rabida), on producing that promising eggsac, and on being so innocuous despite its scary name.

And this one, for such a fine clutch of baby spiders on its back.

There was an Argiope spider, sometimes called a writing spider or zipper spider, to compliment on its writing ability. If it crosses your mind that it might be the inspiration for the spider in E.B. White's Charlotte's Web, the web says you're right.

And then there was a native Euonymus shrub (Euonymus americana) to congratulate simply on being able to produce its ornamental seeds. This shrub is a favorite of deer, which makes this one's health a testimony to the advantages of nurturing nature in the city.

Charter School Planting Possibilities

I've heard the Princeton Charter School may be rethinking its landscaping. This could be good news for any student wishing to get acquainted with our natural heritage of native species. As things are, there's a tightly controlled landscape of trees and turf, with a few little raised beds for vegetables near the staff parking lot.

One promising spot for a narrow raingarden is this ditch next to a walkway.

The island dividing the parking area from Bunn Drive could accommodate a larger raingarden,

as they did on the Princeton University campus behind the new neuroscience building just off Washington Road. Note the curbcut where runoff from the street can enter the concave raingarden. A little weeding out of the foxtail grasses would neaten up the appearance considerably.

What really would be exciting though, and very educational for the kids, would be to work with the office complex just up the hill from the Charter School to turn this big detention basin into a meadow of native grasses and wildflowers. We're talking about a habitat bonanza for birds, butterflies and other pollinators,

and shifting from weekly mowing, of an area that can get very wet, to an annual mowing.

What could be more educational than to show kids how something negative--polluted runoff flowing from a big parking lot into a detention basin that's difficult to mow--

can be used to feed something positive--a wet meadow that provides beauty for us and food for an endless variety of pollinators?

I have already approached the manager of the office complex on Ewing Street about shifting to meadow, but it was nixed by the owner in Texas. If the Charter School approached them, they might react differently. A federal agency, Partners for Fish and Wildlife, has helped in the past with expertise and materials to shift basins from turf to meadow, such as at Farmview Fields.

This is a very do-able initiative for someone at Charter School to explore. I can supply contact info for the office complex manager.

Local PawPaws Ripe

For anyone who hasn't tried pawpaw--our northern representative of a largely tropical family of fruits in the Annonaceae--the Whole Earth Center has some in stock from a local supplier. The harvest only lasts a couple weeks each year, according to one employee. Pawpaws have a short shelf life, and bruise easily, which has long hampered efforts to market them in anything beyond a small scale, local fashion.

I bought one and shared it with my daughter, who had never had one. She said it tastes like a combination of mango and kiwi. Delicious.

You can type "pawpaw" into the search box at the top of this blog to find a couple previous posts on the subject.

Learning from Harrison Street Park's Plantings

In 2010, after years of planning, Harrison Street Park was planted with an ambitious array of native trees, shrubs and flower beds. The goal was admirable enough: Beautify a park that had until then been largely a static assembly of trees and grass, with little habitat and ornament. I was involved in the early stages, providing a detailed ecological assessment and stewardship plan. Princeton arborist Bob Wells contributed a tree survey pro bono. After this input of local knowledge, an outside consulting design firm based in Philadelphia, was brought in to develop plans for plantings and play equipment, with ongoing input from neighbors.

When the planting was finally done, there followed with uncanny timing a deep drought. Neighbors, having committed to caring for the plantings, put in long hours through the summer. Most of the plantings survived that first, heroic year, but then volunteer energy began to dwindle. A couple very active neighbors moved away. Borough maintenance staff couldn't take up the slack because they weren't trained to care for anything other than trees and turf. A professional weeding in 2013 salvaged some flower beds, though many of the planted species had by then been lost. 

And yet, in 2014, with most of the beds a weedy tangle, two of them are flourishing. This raingarden at the edge of the field is weed-free and filled with flowers.

And this planting next to the bridge dedicated to borough engineer Chris Budzinski still looks good.

Why are they prospering while other plantings have been taken over by Canada thistle, mugwort and other aggressive weeds? The answer lies not in how much money was spent, or the beauty of a design meticulously laid out on paper. In fact, the best results were attained without cost or elaborate planning. Instead, success grew out of on-the-ground experience and long observation of how rainwater flows in the park. That flow, whether natural or manipulated to advantage, determined which gardens survived and which ones burned out volunteers by growing abundant weeds.

When I began my analysis of the park, I began here, in the parking lot for a prominent architect's offices. You can see how this parking lot matters if you turn 180 degrees,

and look downhill towards where all the storm runoff from the asphalt flows into the park. This water is so important that, when they repaved the lot a year or two ago, I checked to make sure they didn't add curb and gutter to divert the water into a storm drain.

Why? Because just beyond the fence is a raingarden that I and other neighbors helped Clifford Zink to plant.

In the park's large expanse of grass, the garden (back right) was planted not just anywhere, but strategically located in a sunny swale that receives the runoff from the parking lot.

The periodic infusion of water creates an underground reservoir of moisture. Powered by adequate sunlight and fed by the stable water supply, the native plants prosper. What few weeds manage to survive the competition can be easily pulled from the soft ground. Now, it might have been better if we hadn't planted sunflower species that spread underground and have been steadily displacing the less aggressive swamp milkweed, hibiscus and even joe-pye-weed. But the result is still attractive and very easy to maintain. A well-timed hour or two with a few volunteers pulling out some of the sunflower stems next spring would restore balance. It's worth noting that this successful garden, planted by volunteers at no cost to the borough, was actually slated to be removed by the landscape design firm, which failed to understand its logic and value. Neighbors had to rally to make sure it was not removed.

Of the garden beds added by the design firm, only one has proven relatively easy to maintain, due to it also having been planted in a swale, where wet, sunny conditions favor the natives and make weeding easier.

This shadier planting might have done well with consistent care, but long periods of neglect allowed garlic mustard and Canada thistle to take hold. Apparently worked on this year by parks staff led by someone knowledgeable about plants, it still contained enough of the original foamflower and ironweed to be attractive.

There were other locations in the park with the combination of wet and sunny conditions that favor native wildflower plantings, but these spots were instead planted with trees that cut off sunlight, or raised up in a way that shunned the periodic infusions of runoff that could have keyed their survival. The flower bed in this photo, shaded and raised up on a berm, must have looked good on paper and when freshly planted, but offered none of the sun and natural water needed for the natives to compete with weeds. These berms, hazardous to mow, can't even revert to lawn as most failed gardens do.

So, what's the verdict on Harrison Street Park's grand experiment in planting and caring for naturalistic flower beds?

• Study the way water flows in the park and choose your spots wisely. A poorly situated garden that favors weeds over intended plants will burn out volunteers.
• Rather than plant traditional perennial borders that tend to be elevated and attract weeds, focus on areas that are in swales or depressions, and receive enough runoff and sunlight to power native floodplain species robust enough to outcompete unwanted plants.
• Start small and expand incrementally, making sure that the maintenance work doesn't outstrip volunteer interest.
• Particularly in a place like Princeton, use local talent that feels invested in the park. If a design firm is needed, favor one that understands how water drives landscape decisions, and has had as much experience maintaining flower beds as designing them.
• If town maintenance crews are used, have them supervised by someone trained in plant identification.

This photo captures what has worked well in the park: two rain gardens and the sports field intentionally given a slight crest to shed water. These successes, whether designed to receive runoff or shed it, depended on close attention to "where the water goes."