Whither the Migration of Monarch Butterflies?

Though the number of butterflies in general was radically down this summer, I still saw the occasional monarch. Some appeared frantic. Were they searching in vain for a mate? Other times they'd pause on a flower to take a long drink of nectar. Sometimes I'd just see a flash of orange out of the corner of my eye. No other butterfly can match a monarch's nimble power in flight. The number of sightings, maybe ten in all, wasn't much changed from previous years.

Their longterm prospects, though, are very much in question. Chip Taylor, who has tracked migrations as closely and for as long as anyone, says that monarchs as a species will survive, but their fabulous migration will not. Last year's overwintering numbers on Oyamel fir trees in the mountains of Mexico was the second lowest ever recorded. Resilient as the monarchs are, it's hard to imagine the delicate dynamic of migration surviving the rapidly increasing disruptions of climate change.

Yes, climate has changed in the past. It's said that, before humans started altering the atmosphere, the earth experienced a progression of ice ages every 100,000 years or so. During the last ice age, glaciers extended south almost to what is now NY City. What we have now is change at a speed far beyond the capacity of species to adapt, as our machines pour a massive overdose of carbon dioxide into the atmosphere.

In a blog entry this past August, Taylor explained how extremes of weather can affect the monarchs' capacity to build numbers over the summer and migrate back to Mexico in the fall. Extended heavy rains in early summer can delay egg laying. Warmer temperatures in September and drought in October can impede a fall migration historically aided by cool winds out of the north. What we got this year was hot and dry, with three months of drought and warm weather extending into mid-November. That's a radical departure from anything I've ever witnessed.

Each year towards the end of October, I start looking for news about the migration south to Mexico. The first headline I found confirmed my suspicions: "This fall's monarch butterfly migration through Texas doesn't look promising." Then, finally, a report on-site at the roosting grounds in Mexico. Though a few had been straggling in over the past few weeks, the first largish group of 2000 monarchs wasn't reported until Nov. 21. In past years, monarchs would predictably arrive en masse in the first week of November. Then, after the monarchs had settled into their roosts, the Biosphere Reserve would be opened to tourists mid-month. This year that opening was cancelled, stranding those tourists who had traveled far to witness a unique example of nature's splendor. This is not the only destination being compromised in a world being heated in part by global tourism. There are different ways to show love for nature. Touristic love, which I was a part of in the past, becomes more ironic by the minute.

The radically dry, warm weather we've experience this fall has a lot to do with the increasing instability of the jet stream--high winds out of the west that normally feed us a steady stream of contrasting weather, but can get blocked and diverted north or south, causing weather systems to linger indefinitely. The jet stream is driven by the difference in temperature between the tropics and the arctic. As the arctic heats more quickly than lower latitudes, the temperature gradient is reduced and the jet stream becomes more malleable. 

Consider the extraordinary ambition and brilliance of the monarch butterfly's eastern migration. Huddled overwinter in the mountains of Mexico, its numbers head north in March, then each succeeding generation--usually four total--fans out from Texas to harvest the richness of flowers and milkweed foliage from the whole eastern half of the U.S. and even up into Canada, before somehow knowing how to navigate all of that embodied richness back to their little hideout in Mexico. Over the past million years, the distance flown would have contracted during ice ages, then expanded as the glaciers withdrew. I think of the monarch migration as akin to a rubber band, stretched northward by the supply of nectar and milkweed, then contracting back down to Mexico for the winter.

The vast territorial expansion each summer is surely dependent on numbers. Otherwise, how will the monarchs find each other to mate as they spread out across the continent? Though much different in behavior, the passenger pigeon was also dependent on big numbers. Its demise, more than a century ago, was due to radical habitat change and a wanton harvest and slaughter that Aldo Leopold described as "trigger-itch." Now, our itch is to take photos, and our intention is to preserve. And yet, we watch as the collateral damage of a machine-driven economy accumulates.

A post on the Monarch Watch Blog describes the Symbolic Monarch Migration that school kids in Mexico, the U.S., and Canada take part in. Kids in Mexico send paper monarchs to kids up north in the spring, and vice versa in the fall. Monarchs ignore country boundaries. They are telling anyone who takes time to listen that our interests don't stop at the border, what we do affects people and nature far away. 

One halcyon autumn day when I was a kid, walking across the broad lawns surrounding Yerkes Observatory in Wisconsin, I was astonished by the sight of countless thousands of monarchs flying above me. There was a thrilling collective energy to their flight, not dutifully unidirectional towards the south but instead more like a dance. They seemed to feed off of each other's proximity and energy--an uncanny mix of whimsy, skill, and determination. 

If the great migration were to be lost, monarchs would still persist in pockets further south, but they wouldn't be the same monarchs we've known and loved. Here's a post on how the loss of migration's rigors would change them.

How Are Monarchs Doing in 2024?

Several times a year, the question of "How are the monarchs doing?" rises in my mind. An internet search typically ends up at Chip Taylor's blog on Monarch Watch. There you will find thoughtful commentary and deep analyses, a mixture of good news and bad news, as this extraordinarily resilient species faces ever greater challenges. In 2024, overwintering numbers in Mexico were the second lowest ever recorded, with 2013 having been the lowest. Chip's more recent posts tell of a rebound this summer, as this robust and prolific species has increased its numbers during its migration, following the growth of milkweed north in a tagteam of successional generations, spreading into all corners of the eastern U.S.. 

I've had maybe five sightings of monarch butterflies this summer--a typical number. One appeared frantic, as if it had been searching the great outdoors in vain for a partner. Another was laying eggs on a patch of common milkweed at Mercer Meadows--a beautiful and hopeful sight. Another, pictured, was in my front yard on busy Harrison Street in Princeton, gathering nectar on a swamp milkweed. 

A few days ago, one was nectaring on a patch of narrow-leaved mountain mint near Herrontown Woods. I was treated to a surprising display of butterfly aggression, as several skippers suddenly ganged up to chase the monarch away from the mountain mint. 

Part of that competitive fervor may have to do with the scarcity of pollinator plants. In a 4.5 acre field, there were only two small patches of mountain mint. Since forests don't supply summer nectar, meadows like this are where monarchs and other pollinators are going to find food and each other. Many meadows and roadsides are being taken over by mugwort, Chinese bushclover, and other invasive species with limited utility for pollinators. Add that threat to all the others: habitat loss, climate change, indiscriminate herbicide use in people's yards and along roadsides. This meadow is preserved, but that's really just the first step in realizing the meadow's potential as habitat that can help sustain species like our beloved Danaus plexippus, aka monarch butterfly.

Related posts:

Growing Monarchs

Do Praying Mantises Eat Monarch Butterflies?

Other previous posts about monarchs

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. 

Considering the Chinese Praying Mantis an Invasive Species

In the past, praying mantises of all sorts were looked upon as beneficial insects that consume insect pests. A few things have changed in this regard. For one, insects in general are becoming fewer. My observations haven't been systematic, but I've noticed a steep decline in pollinators in the past few years, and a coinciding increase in insect predators, particularly Chinese praying mantises. And it's a stretch to believe a predatory insect is going to only consume insects that we consider harmful. Last fall, I found one chowing down on monarch butterflies. 

In my backyard I recently found four chinese praying mantis egg cases in close proximity. I'm thinking the best thing to do is to destroy them or put them in the trash. One post that helps distinguish between the different species of praying mantises and their eggcases also recommends feeding the nonnative eggcases to chickens. 

Past posts on praying mantises.

Do Praying Mantises Eat Monarch Butterflies?

It seemed like such a feel good moment, crossing the gas pipeline right of way out at Mountain Lakes. There's a lovely walk up from Mountain Lakes House towards Witherspoon Woods that crosses the treeless strip known as the gas pipeline right of way. 

The opening was enlivened by thistles in full bloom, probably native field thistles, if the whitish underside of the leaves is indicative. And adorning the thistles were multiple monarch butterflies, fluttering as they drank from the flowers. 

It had been years since I'd encountered a native thistle, and I hadn't seen a monarch in several weeks, so to see both together in numbers lifted the spirit. But the idyllic scene developed some disturbing undertones upon taking a closer look. 

There, down the stalk of the flower a little ways, something brown. Do you see it? A big praying mantis, of which there were several. I've long wondered if they could be one reason the monarchs are declining in numbers. 

The answer came quickly. A pair of monarch wings weren't moving, and there, sticking its head out, next to the lifeless remains was one of the praying mantises. 

Here's a clearer angle. 

The Intermixing of Good and Bad

My interest in plants began with organic gardening. When growing food is the objective, praise goes to rich soil and natural predators that eat insect pests. Once my interest turned to native diversity, however, my view of what was good began to change. I noticed that poor soil often harbored richly diverse native plant communities. Too many nutrients could be detrimental. And those natural predators that were keeping pests at bay? Well, the praying mantises we most commonly see are not natural, but were instead imported from China. 

Note: A National Geographic article explores how the praying mantis avoids being poisoned by the toxins in monarch butterflies.

All around the thistles was another invasive, Chinese bushclover, also known as sericea lespedeza or Lespedeza cuneata. I know it well from my years in North Carolina, where it was planted by the Dept. of Transportation as a supposedly good thing, to reduce soil erosion on newly carved road embankments. Proponents claimed its seeds would be a boon for wildlife. It has since become a major invasive pest in grasslands, replacing diverse native species with an inedible monoculture. And the seeds? Reportedly they are too small and pass through the guts of wildlife unutilized.

Its white flowers distinguish it from natives like slender bush clover (Lespedeza virginica), which has pink flowers and is rarely encountered. 

Chinese bushclover is a relatively new invasive in Princeton, but I've seen elsewhere what it can do, and it's only a matter of time before it forms monocultures to rival mugwort. There might have been a time when I would have praised it for its tough roots that hold the soil in place. Being a legume, it has the capacity to fix nitrogen from the atmosphere, enriching the soil. But no herbivore has come forward to limit its rampancy. From a plant diversity perspective, it is a disaster. 

The knowledge that all is not well in the world does not negate the delight in beautiful thistle blossoms and a clustering of monarchs. It just heightens the sense of positive and negative intertwined all around us.

What's Bloomin' in the Barden -- Early July

An effort to document everything flowering in the Botanical Art Garden at Herrontown Woods on one day in June (the 26th):

Black-eyed Susan in the Veblen Circle surrounding the gazebo.

Beebalm

Fringed loosestrife is a shy native wildflower, pointed downwards, but is not shy about spreading.

This is looking like white avens, a native that's also looking pretty shy. We tend to think of it as a weed, because it isn't very ornamental and makes burrs that stick to clothing.

The tiny flowers of tall meadowrue make clouds of white in the Barden, sometimes rising to ten feet. I've found it growing wild in Princeton in only a couple places, but it grows well in a garden.

A few sundrops are hanging on, with their x-shaped stigma. This is an easy flower to grow, spreading a little but not too much.

Narrow-leaved mountain mint is a native wildflower that appeared spontaneously in the Barden. It's a fairly common wildflower of meadows in the Princeton area.

Daisy fleabane was blooming weeks ago and is still at it. There are two species.

The untoothed leaves suggest it is Erigeron strigosus. 

Common milkweed has spread rapidly at the Barden. I just met some Herrontown neighbors who grow milkweed, and their kids have already found two Monarch caterpillars that they adopted and grew into butterflies.

If black cohosh is blooming in the Barden, that means it will soon be blooming in the woods up on the ridge as well. 

Some nonnatives are St. Johnswort,

moth mullein,

 (moth mullein's distinctive buds)

wooly mullein, which can spread by seed quite a bit but we allow a few to grow for their dramatic shape and the velvety feel of the leaves,

and white clover.

A few native shrubs are blooming: oak-leaved hydrangia,

silky dogwood,

and elderberry.

We're being very encouraging of sedges at the Barden, planting them in swales where they get plenty of moisture. They reach a peak of lush, grassy beauty in late spring, and each species has a different shape to the clusters of seeds. There are many species of sedge. I'm going to say this is Carex lurida, the sallow sedge. 

I'd call this the morning star sedge, Carex grayi.

This is a fairly common sedge in Princeton in floodplains. I've long wanted to attach a name to it. Once I thought I'd found a name, then promptly forgot it. The mind is a terrible thing.

Rushes are not sedges, but this green bulrush is a sedge. 

That's 21 species found blooming or fruiting on June 26, 2022. For some, this diversity is off-putting, but for those who love plants, the diversity just makes it all the more interesting.

Nature's "Depressions" Bring Beauty and Resilience

Another in my writings about the ecological, logistical, and psychological aspects of tending to a detention basin at Smoyer Park that we converted into a native meadow. Most of the photos and writing are from mid-July, 2021.

There's a garden that many people pass by but few notice. I saw my second monarch butterfly of the season there in mid-July, attracted to the subtle flowering going on there. It's at the far end of the parking lot in Smoyer Park, out Snowden Lane. Drive or bike down to the lower end of the lot, and by heading downhill, you're essentially following the water, doing what rain does after it hits the ground. And there you will find what most people, if they have any name for it at all, will call a detention basin, so-called because it detains runoff, slowing it down, capturing it in a depression so that it can seep into the ground and feed the aquifer rather than feed a flood.

Bureaucracies require it, engineers designed it, but probably none of them were thinking about what a great place this wet, sunny spot would be to grow native plants. That came later, when another arm of the government, Partners for Fish and Wildlife, worked with me and the town to turn this previously mowed space into what could more aptly be called a wild garden, or a wetland garden, or a wet meadow. 

"Depression" is a word that in psychology may have a negative connotation, and extended depression is surely something one would want to cure. But if you're an artist of some sort, a depression may mean the mind is doing important work at a very deep level, putting things together in a new way that may lead to a burst of creativity, insight, or both. To experience highs, one must be able to experience lows. 

Nature, too, needs its lows, even though depressions in the ground, too, tend to get a bad rap. "Drain the swamp" is a politician's stirring call to clean up the mess inside the beltway, and lots of swamps were drained when they got in the way of expanding our towns, cities, and farms. But as with people, a depression is where nature does some of its deepest thinking and finest work, feeding the aquifer and laying the foundation for foodchains with a rich variety of native plants. Gardeners like to lift plants up in raised beds, but many native wildflowers prefer the opposite, somewhere low down. Those are the seedheads of big bluestem in the photo, a dominant prairie grass in tallgrass prairies of the midwest, historically munched on by bison. 

You can see a fence bordering one of the ballfields at Smoyer Park in the distance, and most of the surprisingly many detention basins scattered across the Princeton landscape, in developments or at parks, are managed like a ballfield, with grass mowed to the ground, though no one would think to play a game there. One thing I've managed to do in town is get some of these converted to wet meadows--first at Farmview Fields, then at Princeton High School, then at Greenway Meadows and Smoyer Park. 

I walked through the Smoyer Park wet meadow in mid-July, to see how it's doing and to do some weeding of this half-acre wild garden. As any gardener knows, there's a lot that can go wrong, even in a meadow that's supposed to grow naturally. Many of these raingarden-like plantings, if untended, fill with a host of aggressive weeds, like mugwort, Canada thistle, and Chinese bushclover (also called Sericea lespedeza). Even natives like blackberry and some kinds of goldenrods can tend to take over.

Nature is complex, which can be daunting and even off-putting, or exciting for those who take an interest and build familiarity one plant at a time. That's where love comes in, because when you love something, you want to know everything about it. Botanists talk about plants like a baseball fan might take pleasure in quoting obscure statistics or reminiscing about certain players. Love turns complexity into joy. Love is also what gets one out there to check up on a wild garden, to make sure it's doing okay.

Knowing how much can go wrong can increase the pleasure at seeing so much going right. Now, this photo shows little in the way of blooms, but a gardener conversant with the species of a wild meadow can experience joy even before plants flower, is moved as much by what will be as what already is. Each stem of a favorite wildflower implies a bud, each bud a flower, and each flower a host of insects that in turn support a foodchain of wild life. 

A botanist gardener can see in this photo the spray of monkeyflowers in the lower left, the burst of rose mallow hibiscus in the center right, and behind them a favorite sedge called woolgrass rising towards maturity. Other species, too, are gaining in number and moving towards bloom--ironweed, partridge pea, blue vervain. From evidence of browsed stems, even the deer's appetites seem in balance, leaving many plants to grow unhindered. The diverse mix of sizes and textures triggers memories of other rich meadows seen--prairies in Ann Arbor, MI, Durham, NC, Chicago. How many people get to travel back in time and across half a continent, just by weeding a detention basin in a park in Princeton? 

Occasionally, a less sanguine thought can intrude. What difference does it make that a half acre meadow is prospering, when a whole planet is so quickly being overheated? Delight in mid-July could not completely eclipse news heard earlier that day, of environmental and cultural devastation in Europe, as an overheated atmosphere unleashed a flood that shattered all records. 

September 12, 2021

Since mid-July, Princeton had its own megaflood when Hurricane Ida swept through the night of Sept. 1. Basements flooded that had never flooded before. The DR Canal towpath was badly damaged, ten years after being similarly damaged by Hurricane Irene, and only two years after being fitted with a fresh cinder surface for walking, biking, and jogging. 

But one place I didn't worry about getting flooded was the detention basin at Smoyer Park. It's built for flooding, and fitted with native plants that have evolved to thrive on periodic floods. Though, being the caretaker, I will be worrying about whether I could be doing more to limit the spread of stiltgrass, carpgrass, canada thistle, blackberry, and various other overly aggressive species, to a passerby the meadow has a late-summer look of subtle earth tone radiance and balance. The white in the distance is late-flowering thoroughwort, mixing with the emerging yellows of goldenrod, a few lingering spikes of purple from the ironweed, and the bronze of tallgrass prairie species--big bluestem and Indian grass. 

Last year's post about Smoyer Park's basin: The Work Behind a Natural-Looking Meadow

Monarchs and a Mid-Summer Multitude of Wildflowers at the Barden

So, I was at the Barden today, that being the Botanical Art Garden in Herrontown Woods, and amidst all the positive energy of budding flowers I had a cynical thought. There are a couple spots around the Veblen Circle of wildflowers where milkweed has been spreading. Lots of leaves and none of them being eaten by monarch caterpillars--an all too common observation over the years. People say to plant milkweed to help the monarchs, but the monarchs aren't helping themselves to the milkweed. What gives? 

As if on cue, a monarch appeared an instant after I had that thought. Only the third I'd seen this summer, it was checking out the milkweed and other plants growing in the sunny openings of the Barden. There are many kinds of native flowers blooming right now, which I'll show photos of later in this post, but the monarch headed over to one in particular,

a buttonbush, whose tiny flowers form the shape of a golfball--a convenient surface upon which the pollinator can go from flower to flower, sipping nectar. For an insect it must be like an assemblage of Hold the Cone miniature ice cream cones, but no need for a freezer. 

Moments later, another monarch butterfly caught my eye, and this one was showing a more intense interest in the milkweeds. There are two types at the Barden--purple and common. Both kinds spread underground, creating clones with many stems--enough to support a whole gang of hungry caterpillars. The butterfly was landing on the edge of the purple milkweed leaves and dipping its abdomen under the leaf to lay an egg. 

After doing this a number of times, it headed elsewhere, allowing me to take a look. Not easy to see. There, in the lower left. 

Here's an egg a little closer up.

There's actually quite a bit going on underneath a milkweed leaf. Here was a whole cluster, which I'm guessing are the eggs of the milkweed tussock moth--another Lepidoptera that can stomach milkweed's cardiac glycosides. 

Of course, it's a hopeful sign to see a monarch laying those single eggs, but we saw this last year, and it didn't lead to any sightings of caterpillars later on. It's possible the eggs are getting eaten by ants and spiders. A complex food web can have its perils, and it's interesting to note that milkweed that once grew in farm fields (in the days before Roundup-Ready corn and soybeans) might have had better monarch survival due to there being less predators in that simplified landscape. 

Still, we can hope that this is the year when the Barden does its part to build monarch numbers in preparation for their perilous flight back to Mexico in the fall.

Another sweet sight today, again not captured in a photo, was the pair of hummingbirds that landed on a wire cage just five feet away. Hummingbirds, in my experience, actually spend a lot of time perching, which makes sense given how intense is their flight. Their presence was the answer to a question overheard at the checkout counter at the Whole Earth Center: "Has anyone seen any hummingbirds?" Like monarchs, they also have to negotiate a difficult migration every year.

Maybe they were attracted to the tubular flowers of wild bergamot, 

or beebalm, or jewelweed.

What follows here is a documentation of all the flowers seen blooming right now in the Barden, as the midsummer diversity kicks in. After all the work of weeding and planting, there's pleasure in simply walking the paths and appreciating all that is growing so enthusiastically. 

There's a lot to document. These signs, created by Inge Regan, offer four species to look for. When learning plants, it's good to focus on a few at a time. 

For those more familiar, we've brought together some 40 species that bloom in mid-summer, some of them shown below. Maybe you can walk the pathways and see how many you can find. We're trying to figure out how to pot up all the excess and make them available to visitors to take home.

To see some of the other species showing their stuff this time of year, click on "read more", below.

In a Hidden Valley, Sudden Abundance, and a White Squirrel

Some of my favorite memories in nature are of sudden abundance. Day to day, walking through a woods or stepping into the backyard, we tend to see one or two of this or that bird or flower. The dispersed, low-key nature we typically see contrasts with accounts from long ago, when endless flocks of passenger pigeons darkened the sky, and herds of bison stretched to the horizon. As a kid, I read of distant streams or lakes teaming with fish. "Where lunkers lurk just below your boat" was one memorable headline. On a few occasions I convinced my father to drive me to them, trips that repeatedly ended in disappointment. 

Serendipity, however, has served up sudden abundance a few times in my life. One fall day early on in my small Wisconsin hometown I was walking home from school when I happened to look up and saw the whole sky filled with monarch butterflies heading south for the winter. There was the small inlet we canoed into in the Quetico, where we happened to look down and saw the shallow water was thick with a school of walleye, from which we quickly caught a delicious dinner. During our time in North Carolina, there was the time when hundreds of cedar waxwings enlivened our neighborhood for a couple days with their antics. And each year in the fall, I'd hope to be around when a large flock of migratory robins, with a few scarlet tanagers mixed in, would descend upon our yard, strip the flowering dogwoods of their ripened berries in an orgy of consumption, then be gone. Even the small park behind our house here in Princeton served one evening a few years ago as a stage for sudden abundance, when winged ants began emerging from the ground, attracting hundreds of dragonflies which in turn attracted a flock of swallows, spectacular fliers all.

This summer, serendipity served up sudden abundance in the most unlikely of places: a hidden valley in Princeton Junction. One afternoon I was standing outside a strip mall with a few minutes to kill, and decided to check out the woods behind the row of businesses. In retrospect, I was just following the flow of the pavement like any self-respecting raindrop would have done, but this going with the flow was taking me away from the human mainstream into another world.

There, beyond the edge of the asphalt, the land dropped down into a woodland like no other I have ever encountered. Perhaps only a botanist would have recognized the extraordinary nature of the nature that stretched before me. Clethra as far as the eye could see. Okay, let me explain. Clethra alnifolia, summersweet, sweet pepperbush, call it what you will, is a native shrub with a fragrant flower sometimes used in landscaping. 

Now, if you're into native plants, you may start to wonder where they typically grow in the wild. Many of the more popular ones--like Clethra, or Virginia sweetspire, bottlebrush buckeye, oak-leaved hydrangia, purple coneflower--have proven rare or non-existent in the wilds I've explored over the years. This could be due to the myriad ways in which we have transformed the landscape, from development to draining to fire exclusion. Or it could be that their home habitat is remote from places I've lived. In the case of Clethra, I had never seen it in the wild save for one sorry specimen holding on next to the towpath along the banks of Lake Carnegie. 

It was a surprise, then, to step behind a pizza joint just up from the Princeton Junction train station, and find myself gazing out on a sea of Clethra, growing like a weed. 

Ostrich fern is another plant I've rarely seen in the wild, and here it too was growing in abundance, giving the woodland a tropical look. 

Returning later with a pair of rubber boots, I waded out into the mud to explore this hidden valley, several times almost losing my boots in the thick muck. 

Here are a few other sudden abundances and rarities--plant, animal, and human--that I encountered:

On the hammocks of high ground surrounded by the mucky soils, Hydrangeas were in full bloom, reaching up to 17 feet tall.

Under a canopy of black gum, red maples and oaks, there were lots of Magnolias

and highbush blueberries.

Netted chain ferns, which bear a resemblance to the much more common sensitive fern, were tucked in among the massings of ostrich ferns.

A small, bent over tree with a curious compound leaf caught my attention. It wasn't a walnut or ash or anything else I could think of. I was excited at the thought that I had discovered a very rare tree, and stumped several botanists before sending a photo to Bob Wells of Morris Arboretum. He promptly identified it as poison sumac--something I hadn't encountered since field botany days in Michigan. The ID explained the skin rash I had been dealing with since handling it.

As with the poison sumac, there was just one Styrax, which showed the remains of its pendulant flowers, and one native azalea. All of these are rarely seen in the wild.

Only towards the other side of the valley did it become clear why this habitat was so different from what can be encountered in Princeton. Most of the stormwater runoff from the strip mall is somehow channeled to the far side of the valley, where it has eroded the stream and exposed the underlying gravel and sand. Simply by crossing Route 1, I had left the piedmont clay of Princeton and entered NJ's sandy inner coastal plain. Though erosion has changed one side of the valley, the other side is fortunately bypassed by the runoff, allowing the mucky soils and hammocks to persist in something close to their pre-development state.  

I had just counted my 30th wild hydrangea blooming in the valley when I saw a man with a white beard walking down into the woods. Scampering about 30 feet ahead of him was a white squirrel. I had already encountered so many unusual plants in this valley, and now I was seeing a white squirrel for the first time in my life. It's distinct appearance lent magnificence to its every move, as if a spotlight were upon it. This photo is the best I could manage with my cell phone as the man continued down the slope. The white squirrel can be seen in the lower right corner. 

He didn't seem to notice me, so I called out to ask him something about the squirrel. He turned and began telling me about a white squirrel he had befriended some years back. It had been a true albino, with pink eyes, and he had trained it to come to him for food. It had gotten to the point where it would come inside. He said that he'd start opening the door for the squirrel to go in his house, and the squirrel would push it further open and come in. He said the true albinos supposedly can't see as well, and that's one reason why it might have allowed itself to be tamed. One day it disappeared, and a friend told him it had been hit by a car. 

The white squirrel I had just seen was one of the albino's offspring. Actually, he explained, they are called silver squirrels, because they have a little gray on their backs, but are otherwise white. Squirrels are really smart, I interjected, expecting him to marvel at how remarkable squirrels are, but my thoughts on their intelligence made him think instead of how you can't keep them out of a house, and how squirrels had gotten into an old neighbor's attic and nearly destroyed her house. He was clearly not one to romanticize animals.

I asked him if this hidden valley is protected, and he said they have had to fight to keep the developers out of it. They lost about 60 feet of it when the strip mall developers wanted to build off the back. Lots of trees lost. He later said there's no organization, just the neighbors who border the property. He had a t-shirt on that said "REAL MEN DON'T NEED INSTRUCTIONS". I asked to take a photo of the shirt, as an excuse to photograph him. He said yes, and pointed out the hammer on the shirt, accidentally cut in two by a table saw. His name was John.

We walked down to the stream, where he said there had been a bridge that got washed out. The bridge turned out to be a long timber, 8x8, which he lifted back into place with some effort, but still impressive for his age. He said the neighborhood is called Berrien City. 

I told him how amazing this valley was for a botanist like me. He said when he'd first heard about the house they bought, and heard it was in Princeton Junction, he pictured something urban. But finding this valley behind it changed his mind. He asked if I'd seen the pond, and when I said no he offered to show me. 

As we maneuvered through the woods thick with sweet pepperbush, he began telling me about his early days, living on the outskirts of Langhorne, PA. He had wanted to be off the grid back then, bought a house that hadn't been lived in for 30 years, had a hole in the roof, one bedroom, a living room and a kitchen. They had a 2 year old son. Their water came from a spring up the hill. A number of them living there dug underground pipes to direct the water to their homes. He said he was at the bottom of the line, and had 600 feet of regular garden hose that the water flowed through to get to his cisterns--one of concrete and two of stainless steel. The cisterns were always full and overflowing, and to keep the water flowing through the hose in winter he had to keep the faucet open in the kitchen. If the hoses froze, he had to gather up all 600 feet and bring them in next to his woodstove to thaw out. He heated completely with wood until their son was seven. The house had 30 amp service, and there was some sort of radiant heater he could turn on to warm the outhouse seat before he headed out there in the winter. They heated water on a stove, and bathed in a tin tub in the kitchen. They ate squirrel and raccoon. The raccoon, he said, actually tasted good. A possum they tried, though, tasted like a McDonald dumpster. He still chops wood. His son, a policeman, still heats his house with wood, even though they have a regular furnace. His son uses a woodsplitter, though. 

The subject of raccoons got him talking about how he used to pay his mortgage with roadkill. Raccoon pelts fetched $50 back in 1980, and fox $75. He'd keep them in his freezer, skinned or sometimes not, until he had enough to make a delivery. It didn't take many to come up with 300 bucks. 

John told me more stories as we stood next to the stormwater pond, in this otherworldly valley hidden behind the loading docks and clustered storefronts of a strip mall that looked like any other in America. I wished I had turned on my phone's recorder to capture his voice and more fully document his story. Much of it involved his life in the fur trade in the 1980s, driving fur traders along a circuit from NY City out to North Carolina, north to Ohio and Pennsylvania, then back to New York, sometimes with $100,000 worth of furs in the back of the truck. It sounded like an updated version of trade in the 18th century. As a line of work, it probably met its demise in the 1990s, when animal cruelty concerns came to the fore. And I doubt a mortgage could be paid off in the 21st century with roadkill. 

Heading back to my pickup afterwards, as if to bend my mind once more before emerging from the woodland, I saw another white squirrel, or perhaps the same one, racing up a tree.