Monarch Butterfly Update -- July, 2023

How many monarch butterflies are people seeing this year? I've seen a grand total of two thus far. Neither paused for a photograph, so this picture is from a past year. 

On July 11, I saw one flying crazily at the Barden. They are expert and often seemingly whimsical flyers, but this one's flight was unusually frenetic. At double the usual pace, it would approach flowers but not land on them, leading me to speculate that it was looking for a mate rather than nectar. A useful Q&A post at JourneyNorth.org suggests that these episodes of particularly erratic flight are induced either by a predator's attack or by a male chasing a female. But the frenetic flight made me instead imagine what it is like for monarchs when their numbers are few, and the search for a mate consumes more and more of their energy. Might a fruitless search at some point become frantic?

A few days later, I saw a monarch in a pasture near Herrontown Woods, flying at a more measured pace. 

There were a few common milkweeds growing in the pasture, but I was particularly happy to discover a couple specimens of green comet milkweed (Asclepias viridiflora), growing there as well. It's a species I've only seen twice in Princeton, the other incidence being a few individuals in the Tusculum grasslands. 

It's common to think that monarchs gain all their sustenance from milkweeds, but in fact the adult butterflies obtain nectar from a broad range of flowers. Otherwise, they would starve after the milkweeds have finished blooming. The caterpillars, however, are highly particular, and will only eat the foliage of milkweeds. The milkweed foliage is around all season long for the munching, though a lot has to happen for the foliage to actually be put to use. A female needs to lay eggs, and those eggs need to elude predation long enough to hatch. I have not seen an actual caterpillar in years, nor much evidence of milkweeds being consumed, but clearly a few are surviving somewhere.

To get a more in-depth report on the status of monarchs, my go-to is the savant Chip Taylor, who blogs at MonarchWatch. In a June 14 post, writing about whether monarchs will be listed as threatened or endangered, Chip Taylor wrote openly about the eventual end of the great monarch butterfly migration. It's believed that the monarch itself is not likely to go extinct, but that the migration--involving the portion of monarchs that participate in the fantastic journey north from the mountains of Mexico up into the U.S. and Canada, then back to Canada in the fall--is increasingly vulnerable. According to Taylor,

"As applied in this case, extinction refers to the loss of the monarch migration and not the species per se. Given the link between the increase in greenhouse gas emissions and increasing temperatures and the world’s slow response to these changes, yes, the monarch migration will eventually be lost."

It's important to note that those who raise alarms about the climate crisis are the optimists. It is optimistic to face up to a grave risk, and call for action to save what will otherwise be lost. Denial and dismissiveness are rooted in pessimism. They take a gloomy view of 1) our capacity to recognize dangers and 2) our capacity to act collectively to prevent catastrophe. Taylor's recognition of the high likelihood that we will lose the migration raises an obvious question, which he hastens to answer.

"If the monarch migration will be lost eventually, why make great efforts to sustain it? Faith. We have to have faith that the world will come to its senses and work collaboratively toward the reduction of greenhouse gases to save the natural systems that sustain us. There is hope. The rate of increase in CO2ppm has declined in recent years."

Another answer is that, the longer the migration can be maintained, the longer humanity has to "come to its senses." 

It is stunning, knowing the extraordinary power of carbon dioxide to influence the earth's climate, that society has left it unregulated. As individuals, cities, and businesses, we remain free to pour as much of it as we please into the atmosphere. Until that giant hole in our regulatory protections is patched, the vast majority of people will not change their behavior. 

A New Invasive Plant at Princeton High School

Here's a story about how an invasive nonnative plant can be accidentally introduced and quietly transform an area. It also shows how invasion can be regional but also very localized.

This is a big picture of a little yellow flower called birdsfoot trefoil (Lotus corniculatus). The clusters of flowers and especially the subsequent seedpods resemble the shape of bird's feet, and the tiny leaves echo this shape to some extent.

I hadn't knowingly seen it much, and only learned the name a couple years ago, but this year, 

it has spread aggressively along the grassy extension along Walnut Street at Princeton High School. I'd noticed a few the year before, but now it is dominant along a stretch in front of the Performing Arts wing and the Ecolab wetland. 

This year also, it is coating areas of an old pasture next to Herrontown Woods. In the pasture, it was probably planted intentionally as forage for cattle, but at the school, it surely was introduced accidentally.

Should we be concerned about either example of this nonnative rampancy? I sent an inquiry to a couple listserves of land managers, and received a tepid response. Birdsfoot trefoil is mostly a roadside weed, was the sentiment. It only gets a couple feet high, so will likely just stay in the background rather than stifle native species. 

But I have a vivid memory of a prairie walk I went on last year at the Kishwauketoe nature preserve in my home town in Wisconsin. At one point, leading us through a gloriously restored prairie, the botanist spotted a birdsfoot trefoil and immediately went over and pulled it out. Was it merely a pet peeve, or was his determination rooted in past observations of dramatic consequences if birdsfoot trefoil is allowed to spread? 

This short video shows how birdsfoot trefoil can alter the appearance, if not necessarily the composition, of a meadow:

I did a quick survey of school grounds and the nearby neighborhood by bicycle, and discovered that the infestation is limited to grass next to the extra wide sidewalks that were installed along Walnut Street a couple years ago. It probably hitchiked in on machinery or soil used in construction of the sidewalk. Another possible vector was the planting of new street trees right where the birdsfoot trefoil growth is now the most dense. Rootballs, topsoil, tools, heavy equipment--all can carry weedseeds.

This is an invasion that's in the very early stages, and could be easily nipped in the bud. For instance, I found a grand total of three plants on the middle school grounds. Five minutes of spot spraying with a selective herbicide now is all it would take to stop an infestation that will otherwise become intractable.

Another reason to take action is that it is poised to invade the new native meadow planting in the detention basin next to the tennis courts. In this photo, a few plants of birdsfoot trefoil grow just across the parking lot from the new native planting. Does the school want a native meadow, or a meadow that is thick with a nonnative species that appears capable of outcompeting many of the native grassland plants? 

Now, while the extent of the spread is limited, would be the time to take proactive action. 

Nash Park in West Windsor Needs a Loving Heart

There's a curious park that I stumbled upon in West Windsor called Nash Park, named in honor of the Nobel Prize-winning mathematician, John Nash, and his wife Alicia. They were longtime residents of West Windsor before being tragically killed in an auto accident in 2015. 

When you walk around this expanse of mostly grass, you may get the feeling that something is missing. What is it? Stewardship? Practicality? Trees?

In reading articles generated in 2017 soon after the park was introduced to the world, I've been able to piece together the original intent. I had been calling it "John Nash Park," but the more powerful story very much includes Alicia. 

As the Town Topics described it in 2017, "Mr. Nash, a senior research mathematician in the Princeton University mathematics department and winner of the 1994 Nobel Prize for economics for his work in game theory, suffered from paranoid schizophrenia and was the subject of the Academy Award-winning 2002 film, A Beautiful Mind. Mrs. Nash, a mental health advocate, was credited with saving Mr. Nash’s life during his prolonged illness."

The West Windsor mayor at the time, Shing-Fu Hsueh, saw the park as a means of showing appreciation for all that John Nash contributed to mankind. He said that John Nash's story demonstrates how “Even though you have problems, you can be recognized around the world.” 

In a Community News article, township landscape architect Daniel Dobrimilsky described the initial concept, “a town green with gardens along the edges. We decided to make the space in the middle the size of a regulation croquet lawn, about a 100 feet by a 100 feet." Croquet! Now I know that I am not the only person in the universe who has long harbored a sentimental affection for croquet.

Dobrimilsky also talked about the desire to improve social life. “One of the concepts we came up with was a community garden, since it is a nice way to share traditions and understand each other better. So I came up with the idea of having an Asian-themed garden, because we had a growing Asian population, and most of the landscapes in the area really followed traditional European designs." An interview with the mayor describes him as one of the first Asians to be elected to public office in the U.S. Shing-Fu Hsueh left his position as a water quality engineer at the DEP soon after  beginning what would be a 16 year stint as mayor of West Windsor, from 2002 to 2018.

Now, six years after those articles and five years after Hsueh's departure, I see no croquet, nor any gardens beyond a shrub or two. A Grounds for Sculpture-like statue of the Nashes walking through the park side by side, for which $190,000 would have needed to be raised, has not materialized. (Update: As of 2023, a less costly version is still being pursued.)

But a number of features have sprouted on this flat square of land that otherwise has no features of its own. The Lions Club installed this welcoming sculpture.

A donated pavilion stands in the back, with a couple benches facing away from the park.

The most interesting view from the benches is up into the pagoda structure above. A plaque explains that a similar pavilion was built in Mount Emei, China, where Nash once gave a lecture. 

An eagle scout project is another landmark, adding a zig and a zag to the path that circles the park, crossing over what could be imagined to be a sandy streambed. 

And then there's this linear feature, with benches at either end as if for spectators to watch some unknown sort of sports event. 

Nothing is explained, beyond a plaque that describes the park as "A beautiful place for a beautiful mind and a loving heart," a sentiment borrowed from Sylvia Nasar's biography of Nash, "A Beautiful Mind."

Picnic tables, this one painted with a faded chessboard, sit out in the field, unshaded by trees. 

The few trees, like this golden rain tree, are planted far from the seating, and look stunted.

Take a close look at the base of the trunk and you'll see why the trees aren't growing much. Evidently, the maintenance crew, in its efforts to kill weeds around the trees, has girdled the trunks with its weed whippers. 

Some tree trunks also have badly damaged trunks, whether from rubbing by deer or sun scorch. 

The park appears well positioned between business and residential neighborhoods, and maintenance crews are keeping the park neat and clean--in a kind of holding pattern. But the needs of both plants and people seem to be getting left out of the equation. As a mathematician might say, those are key variables that must be included in any equation for success. The picnic tables are unshaded. The benches in the pavilion aren't oriented to encourage socializing. There's no place for kids to play and explore. Is there a clear place to park, and a water source for anyone wishing to nurture new plantings? 

The park clearly had an inspired beginning, but now it needs someone who loves plants and loves people, and who can create spaces within it where people will naturally want to gather, and enjoy each other and the landscape around them. Like the troubled genius John Nash himself, Nash Park needs a loving heart.

Harrison Street Park: Contrasting Tales of Trees and Wildflowers

Most people drive by Harrison Street Park unawares. It's an old neighborhood park that lacks parking, and so mostly serves those who live close enough to walk there. Whenever I think to stop by this surprisingly spacious park close to Nassau Street, it's to check in on dreams living and remembered. 

One dream is bringing back the American chestnut. We've planted a number of chestnuts around town that are 15/16th native. They were originally crossed with a resistant asian chestnut, then backcrossed with the aim of ending up with a predominantly native chestnut tree that still carries the Asian species' resistance to chestnut blight. Some of these trees have proven susceptible to the blight, but two in particular have resisted the blight thus far. One of these is in Harrison Street Park, nearly 20 feet tall now. 

We also planted two native butternuts there, another native tree that has been marginalized by an introduced disease. It's good to see them thriving and starting to bear nuts. 

There's also an attempt by the town, successful thus far, to keep a grove of ash trees protected from the introduced Emerald Ash Borer, via systemic applications of insecticide. Another small grove of trees was planted through a citizen donation and collaboration with the Shade Tree Commission.

Other dreams for Harrison Street Park, involving wildflower plantings, have not done so well. Princeton Borough had great dreams for this park at one time. In 2006, they hired me to conduct an ecological assessment and write a stewardship plan. Then they hired a landscape architecture firm from Philadelphia to design improvements to the park. Neighbors offered many ideas and expressed many opinions. The old wading pool--a relic from a distant, more sustainable era when kids gathered in their neighborhood parks in the summer--was removed, the play equipment was updated, and a few new features were installed. 

Some $30,000 was spent on new native plantings that looked good for a year or two before going into steady decline. The idea was that neighbors would care for all these new plants. Of course, a drought promptly ensued. Some of the neighbors rose to the occasion to keep the plants going, but the extensive flower beds required more than an initial season of zeal. Neither the borough maintenance crews nor any of the neighbors had the training or interest to keep the flower beds weeded over the longterm. 

This flower bed is now a massive stand of Canada thistle and mugwort. 

The plant with the big leaves is a common weed in the midwest that is showing up more and more in Princeton. It looks like rhubarb, but is in fact burdock. 

There's a swale in the park that receives runoff from a private parking lot next door. These wet, sunny spots can tip the balance towards native species. A friend and I planted various floodplain species--joe pye weed, tall meadowrue, etc--but also planted Jerusalem artichoke, which is a native sunflower species with edible tubers. 

When planting an aggressive plant like a native sunflower, it's easy to believe one will follow up and keep its expansionist growth in check. That's almost never the case. The sunflowers has spread aggressively underground over the years, and have long since swallowed the other wildflowers in their dense growth. Each year the sunflower clone expands, as park crews mow around its fringe. 

We also planted a couple pawpaw trees there, but they were overwhelmed by the sunflowers. A couple black walnut trees sprouted on their own and had much better luck, somehow managing to rise above the sunflowers. Trees that plant themselves tend to be more successful than trees planted by people. On the upside, the sunflowers are so aggressive that they require no weeding, and there's a dazzling display of yellow in the fall. But, like some of the other plantings at Harrison St Park over the years, it's not what was originally envisioned. 

Sedges Have Edges, and the Blessing of Wet Ground

Sedges are an acquired taste that, once acquired, deepens the pleasure of botanizing. They are grasslike plants that show their beauty not through color but through architecture. Many of them flourish in wet ground. Perhaps the most famous sedge is papyrus, which we were all taught was used by the Egyptians to make paper.

In New Jersey, we have lots of native sedges. One of my favorites is the fringed sedge (Carex crinita). I planted one in the mini-raingarden in front of the Whole Earth Center, along Nassau Street. I guess it looks like a grassy blob, but if you look more closely, 

you'll see it has these pendulant clusters of seeds that look like fingers. The fringed sedge's graceful aspects disguise the toughness at its root, so to speak, as it holds fiercely to the ground. That and its capacity to thrive in wet ground makes it very useful for stream restoration projects.

To distinguish a sedge from a grass, take a close look at the stems, which aren't round like a grass but instead are triangular in cross section. "Sedges have edges" is a fun way of describing the stems. Roll the stem between your thumb and forefinger and feel the edges. Some sedges have more rounded edges than others.

In a much larger raingarden that I manage, over in Smoyer Park, there's a massing of sedges that look like a sea of grass with little pompoms on top. I had been repeatedly forgetting the name of this one, so I was happy to see my "Seek" app (a version of iNaturalist) identify it as squarrose sedge (Carex squarrosa). 

Sedges, like all plants, encourage you to look closely and make fine distinctions, which can help your thinking in other aspects of life. This one probably looks a lot like the squarrose sedge, but the seedheads are a bit heftier. My Seek app is calling it hop sedge (Carex lupulina), which I'll go with. We botany types are often in our own orbits. It really is transformative to have a fellow botanist in the form of a cellphone to carry around in your pocket.

This one has elongated seedheads in clusters. I'll call it sallow sedge (Carex lurida). 

Another sedge I've been dividing and moving to new locations--in my front yard and at the Barden in Herrontown Woods--has distinctive seedheads that look like stars. Having enjoyed calling this morning star sedge, I was surprised to find Seek calling it Gray's sedge, but these are just two common names for the same plant, Carex grayi.

There are other sedges that you're likely to encounter if you gravitate like I do to wet, sunny places. Green bulrush and woolgrass are sedges that were obviously named by people who couldn't tell a sedge from a rush from a grass. Feel the edges, people. 

So-called woolgrass is one of my favorites. This photo was taken at the Barden, later in the season, after it has developed its wooly inflorescence. Unlike most sedges, which mature early in the season, woolgrass grows taller and over a longer arc of time, with attractive features at each stage of development. 

One sedge you're less likely to encounter is tussock sedge, which I've only seen in a springfed marshy area of Mountain Lakes that is unfortunately inaccessible via existing trails. 

Often contrasting beautifully with the light-green leaves of sedges is the deeper green of soft rush (Juncus effusus), which here in the Smoyer Park detention basin has achieved a lovely vase-shaped form decorated with pendulant clusters of seeds reminiscent of earrings. I've seen soft rush used as a striking specimen in gardens--not bad for a native plant that mostly hangs out in ditches and other low ground. 

Sedges have edges; rushes are round, meaning that rushes have rounded stems.

Another reason I like sedges so much--along with other plants they associate with in wet, sunny places, like this Hibiscus (moscheutos)--is that so many native plant species thrive in wet ground and full sun. That, and the soft ground that facilitates weeding, makes for less work and more time to gaze across the expanse and appreciate the beauty. 

Poison Hemlock Popping Up in Princeton

When mathematician and Herrontown Woods volunteer Robert Budny reported that he had found lots of poison hemlock growing in his yard in Princeton, I was at first surprised. I somehow got it in my mind that he was talking about water hemlock--a rarely encountered native wildflower, of which I have come upon a grand total of one growing in Princeton's preserves. 

Robert was quite sure of his find, and said he'd experienced skin irritation while cutting the numerous plants down.

Then I saw this patch of white along Snowden, which too was surprising, since I pass there almost daily yet had never noticed before these tall plants covered in blooms. Maybe it was Robert's sharing of his backyard encounter that primed my eye to take notice.

These, too, proved to be poison hemlock, with broad disks of tiny white flowers. 

and lacy compound leaves. Other plants with white disks of flowers this time of year are the shrubs elderberry and silky dogwood, but they don't have finely dissected leaves like this poison hemlock. 

Though Princeton has many invasive species, those in the carrot family have been few. Goutweed spreads through some gardens. It gets mixed in with the intended plants and can be very hard to eradicate. My neighbor up the street was somehow able to do it, though, through sheer persistence. Wild carrot (Queen Anne's Lace) shows up occasionally along roadsides. It's a beautiful plant, but I've seen it become too much of a good thing in the midwest. Here's information on which members of the carrot family behave invasively in Wisconsin. It includes a useful description of this plant family.

"Many members of the carrot family (Apiaceae) are invasive in Wisconsin. These herbaceous biennials and perennials have alternate, compound leaves with sheaths at the base of leaves. Many small, 5-petaled flowers are arranged in compound umbels (several small umbels combine to make larger umbels). Of the species that are invasive, all have white flowers except wild parsnip, which has yellow flowers. Seeds form in pairs and stems are hollow at maturity."

There are other invasive plant species that, entrenched elsewhere in NJ, are just starting to show up in Princeton. Jetbead and Mile-a-Minute are examples. Catching these early and preventing them from spreading means fewer aggressive plants for gardeners and preserve managers to deal with in the future.

Related posts:

Pulling Jetbead

Mile-a-Minute Spreading into Princeton

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.

Some Flowering Trees and Shrubs in Mid-May

A whole lot of white, and a little red right now. Here's fringe tree

and pagoda dogwood

Red buckeye is a small tree that makes a big show here and there on residential streets. I've only seen it growing wild along a back road in the North Carolina coastal plain.

pawpaw hanging promisingly

This fragrant snowbell (Styrax obassia), was planted by Bob Wells behind Veblen House in Herrontown Woods.

And across the street from me, a horse chestnut puts on a dazzling display, with flowering, towering black locusts adding lofty blooms behind.