The Mystery Tree Found in Autumn Hill Reservation

Not everyone gets to discover and report on a new invasive species in one's adopted home town. Though there were a couple kinds of invasive plants that I caught early enough to hopefully keep from spreading through town--thorny mile-a-minute and more recently the dreaded common buckthorn--this particular discovery is different, in that people have yet to agree on what it is. How strange it can feel, in a time when the internet can instantly tell you everything about everything, to find a plant to which no one can with certainty give a name.

I first encountered a single specimen of the mystery tree while conducting a plant inventory in Roger's Refuge in 2007. Only in the past few years have I found it proliferating in Herrontown Woods and Autumn Hill Reservation. 

Some call it a shrub, though when it grows to 30 feet, maybe it's time we start calling it a tree. There's agreement that it is in the genus Pourthiaea--a name that people will struggle to spell and pronounce (my attempt at a pronunciation is "pore-THEE-uh"). In a discussion on iNaturalist, the citizen science site for reporting and identifying species, some try to call it asian photinia (Pourthiaea villosa)--a nonnative shrub that likely escaped from Princeton-based nurseries long ago.

They are surely wrong, as the leaf shape and fall color of asian photinia are clearly distinct. This bright golden yellow is increasingly prettifying and clogging Princeton's greenspaces, from the Institute Woods in the west to Autumn Hill in the east, creating dense, exclusionary stands as it spreads beyond Princeton to proliferate across New Jersey. 

John L. Clark, a Princeton-based botanist frequently posting on instagram from the forests of Equador, has done a great deal of research into our mystery tree. Since the Pourthiaea genus originated in China, John tracked down a couple Chinese botanists to seek their insights. 

One, D.Y. Hong, responded that he was too old to take on the challenge of identifying the tree.

Another, Bin-Bin Liu, was also apparently unable to assist. John laments that botanists now trained in phylogenomics can identify gene sequences but not the actual physical plants themselves. 

There have been various species names thrown at the mystery tree--lurida, lucida, arguta--but none clearly stick thus far. Through Mike Van Clef, I learned of Jean Epiphan, a northern NJ plant expert at Rutgers, who had arrived at the species name "parvifolia", and even came up with a common name, "littleleaf photinia." Originally introduced in 1908 at the Arnold Arboretum," it's popping up in Morris County and, according to Jean, matches our mystery tree in Princeton. She has not seen it being sold in nurseries, and speculates that it is spreading from specimens in old estates. She sent a couple links (here and here) with descriptions, and a mention of it in Dirr's encyclopedic Manual of Landscape Plants.

Some sticking points, though, are that the link she sent to a photo has now gone dead, and the description is of a shrub less than ten feet high. A photo sent by Pat Coleman from Bowman's Hill Wildflower Preserve also matched our mystery tree in Princeton, but no word as yet whether they've come up with a name.

One thing to call the mystery tree is pretty, as are many invasive shrubs, both when they bloom and in the fall. This fall in particular, Autumn Hill Reservation was a jubilant jumble of colorful invasive shrubs, led by the bright red of winged euonymus, joined by the rich colorations of Linden viburnum and the golden yellows of the asian photinia Even the lowly privet got into the color game with an appealing dark bronze. 

When surrounded by such a dazzling visual display, it takes work to remind oneself that something important is being lost as these introduced species gain dominance in the understory. Their success and dominance is enabled in part through being rejected by deer, which prefer a diet of native plants. Thus, our eyes are well fed while the wildlife find themselves living in an increasingly inedible forest. 

As we lose many of the native trees dominating the canopy--chestnut, elm, ash, and now the beloved beech--the extra light reaching the understory drives the extravagant growth of nonnative shrubs. Surrounded by such a thorough invasion of nonnative growth, it is extraordinarily intimidating to contemplate the work involved to shift the balance back to the spicebush, blackhaw viburnums, blueberries, hollies, sumacs, and other natives currently getting smothered beneath the rising tide.

Native shrubs and trees don't exactly lack color. Here's a dogwood that was mixed in and easily confused with the mystery invasive. Note the way the leaves are paired rather than arising one at a time along the stem. 

All the invasive shrubs currently dominating were at one time, long ago, in a similar state, just starting to pop up here and there. Clearly there was no one back then able to see the future and take early action. In our era, the consequences of inaction are readily apparent. What is special about this moment in the history of Autumn Hill Reservation is that the mystery tree is still early enough in its invasion, and easy enough to spot in fall, that it can be stopped.  

Update:

Where found thus far:

• Rogers Refuge, Herrontown Woods, and Autumn Hill in Princeton
• Possible sighting in the Institute Woods in Princeton
• Bowman's Hill Wildflower Preserve
• Jockey Hollow and the NJ Brigade Area in Morris County
• Tourne Park, in Boonton

Fall Colors Nature Walk, Sunday in Herrontown Woods

Early November, and it's time for a nature walk through the color-coded forest of Herrontown Woods. Color-coded because each tree and shrub is showing distinctive coloration that can make it a snap to identify, even from great distance. 

The walk will head out at 11am this Sunday, Nov. 2, from the gazebo at the Botanical Art Garden (Barden), next to the main parking lot, 600 Snowden Lane. The walk is free, but donations to the Friends of Herrontown Woods are welcomed.

Come early and enjoy coffee and baked treats at May's Pop-up Cafe in the Barden from 9-11, and with all the fall colors, take part in an art project called the Community Collage. 

Along with colorful leaves--still on branches or lying in a colorful collective on the ground--we'll see the bright berries of Hearts 'a Bustin'. If you look closely, you'll even see witch hazel in full bloom. 

Here are four native shrubs that have shown particularly bright fall color: blackhaw Viburnum ("blackhaw" means black berry),

a highbush blueberry along the Veblen House driveway,

winged sumac (a "volunteer" that popped up at the Barden),

and a particularly showy Hearts 'a Bustin' in my backyard.

Nature Stories Preserved in Elric Endersby's Recollector

One way to celebrate the life and work of historian and preservationist Elric Endersby, who passed away October 13 at age 79, is to read the Recollector--an oral history journal that Elric founded in 1975. The nation's bicentennial was approaching--a good time to capture the stories of life in Princeton's earlier days. In the archived version available on Papers of Princeton. I typed in the keyword "Herrontown," and up popped seven articles that provide a slice of life in earlier days, including hikes to Devil's Cave in Witherspoon Woods.

Particularly nature-oriented were Dorothy Compton's reminiscences in 1978 of early Girl Scouting in Princeton. She had her first troop in 1929, back when Princeton was far more rural, before fields grew up in either trees or houses. 

What awaited the girls, as they explored the Princeton landscape and beyond, were the "quavering of a screech owl's song," a "Wild Plant supper" with pokeweed and sassafras tea, and the formidable challenge of making a fire in the woods after three days of rain, while leaving behind "nothing but our thanks." Without the initiative of Elric Endersby, this and many other stories from another era might never have been told nor survived. There was a time in Princeton when people could enjoy nature without fear of Lyme disease, when kids camped in town, and stars filled the night sky. Here are some selected stories from Dorothy Compton:

First and foremost we were an outdoor troop, for that is the real fun of Scouting. We hiked all over Princeton to Devil's Cave, to Carnegie Lake, to Stony Brook, to Guinn's Farm on Herrontown Road. We bicycled to Rocky Hill, car-hiked to Cradle Rock ...

Camp cooking was included on most of our hikes, winter as well as in warmer weather. If a tin cup of cocoa was so hot it burned the lips, it could always be set in the snow to cool. The names of the concoctions we found in our guide books! angels on horseback, galloping guinea pigs, spotted dog, poet and peasant, blushing bunny, squaw corn, corn pancakes, hunter's and komac stew, and many more. Flavored with wood smoke, food by any name was manna to those who gathered the wood and built the fires themselves.

Occasionally it took longer than planned to bring fires to cooking heat, and I well remember one trip to the cave when it was dark by the time we had carefully extinguished every ember and left "nothing but our thanks." There was that long and stony path from the cave to the road, to be traversed in darkness. There was but one flashlight in the group, (and it wasn't the captain's!) But the girl who had followed the motto "Be prepared" led the way, and holding hands in a chain we made our way out safely.

... our Princeton girls enjoyed the priceless experience of living in tents, face to face with nature day and night, learning the self-reliance and resourcefulness that living in the open brings. Have you ever had the honor of being selected to go on a "rain hike" after three days of downpour in camp? Of digging tinder out of the center of a rotting log and peeling standing dead wood to get dry centers to cook lunch? The satisfaction of securing a glorious fire under those circumstances!

Did you ever sleep under a mosquito net canopy on top of a hill, waking by alarm clock every two or three hours to watch the changing positions of the constellations? Or dropping off to sleep to the serenade of a grasshopper perched on top of your mosquito net? Or awake at midnight to find a wandering horse snorting at the strange objects in his pasture? Have you sat breathless around a campfire, delaying Taps, while a camp handyman answered the quavering of a screech owl's song, luring it closer and closer until it perched on a branch just overhead? These and a thousand and one other adventures are the never-to-be, forgotten moments of discovery and appreciation and wonder that come to a Scout in camp.

One of our prize projects was a Wild Plant supper prepared one April evening. Our menu? Dandelion sandwiches, raspberry jam sandwiches (from wild berries, made the summer before), dandelion greens wilted with bacon, pokeweed with sour sauce, sassafras tea, sweet flag candy. Needless to say, the occasion was unforgettable.

Related posts:

Gleanings on Herrontown Woods from the Princeton Recollector

Buckthorn--A New Highly Invasive Shrub Found in Princeton

For years, I've traveled between Michigan and New Jersey and noted how some invasive plant species that have run rampant in the eastern U.S. have yet to show up in the midwest. That is changing. Last year, I encountered a dramatic example of stiltgrass spreading down a hillside in Michigan, and there are reports of lesser celandine gaining a foothold there as well. Similarly, Princeton had remained free of the common buckthorn--the most invasive shrub clogging midwestern forests. That, too, is changing.

The fateful day came on September 16, 2025. I was standing in a spot I'd passed by many times, near the entrance to the Herrontown Woods parking lot, when I happened to look down and saw that characteristic leaf of common buckthorn--the first sighting, by me and perhaps anyone, of this uber-invasive shrub in Princeton. 

The leaves of common buckthorn (Rhamnus cathartica) have arc-shaped veins, and are described as "sub-opposite," because they can appear to be paired on the twig but are slightly staggered.

Buckthorn gets its name from the two terminal buds, which make the shape of a buck's hoof, with a thorn-like protrusion between them.

This photo from upstate NY shows there can be thornlike protrusions along the trunk as well.

Shunned by deer, buckthorn's combination of massive seed production and shade tolerance allow it to clog forests and bury whole native plant communities under its dense growth. The richly diverse bur oak savannas of the midwest were nearly lost beneath a rising sea of buckthorn. Only botanical sleuthing and the hard work of clearing buckthorn, honeysuckle and other invasive plants from beneath the massive oaks, along with reseeding and prescribed burning, has brought back that plant community. 

The small cluster of young shrubs I spotted at Herrontown Woods has fortunately not yet produced seeds. But anyone who has lived in the midwest knows the potential of buckthorn to grow, seed and spread.

An email to the Stewardship Roundtable group of land managers in NJ yielded some responses. Duke Farms has it, as does the Watchung Reservation. The Friends of Great Swamp have an info sheet on their website, so I suspect it has established itself there as well. Mike van Clef, who deals with invasive plants all across New Jersey, writes: 

Duke Farms definitely stands out! From iNaturalist, there are 64 research grade observations, heavier toward northern NJ but all over the state. I often find it as single immature individuals, especially in northern NJ...which is always a head scratcher because I never seem to find a nearby large fruiting individual...

This photo shows the lingering green of buckthorn in upstate NY. Like many invasive shrubs that evolved in a different climate, buckthorn keeps its leaves longer that native species in the fall. 

Given New Jersey's already long list of invasive shrubs clogging our forests--among them multiflora rose, Photinia, privet, and Linden Viburnum--it's hard to imagine another having much of an impact. Having seen what buckthorn does in other areas of the country, all I can say is "Watch out!"

Early detection and rapid response are key to stopping biological invasions. This is true both of the immune systems protecting our bodies and of land managers caring for nature preserves. At Herrontown Woods, we've done very well with that creed of early detection and rapid response. Lesser celandine and garlic mustard--the bane of many a nature preserve--are now vanishingly rare. Vigilance each year in August has helped keep many areas free of stiltgrass, the most rapid spreading of all. People who care and take action can make a difference.

On a town-wide scale, some early interventions have helped keep the thorny Mile a Minute vine from spreading across Princeton. Though Princeton has hired contractors to help counter at least some invasions in their early stages, it's hard to get private residents--often disconnected from the yards they own--to act collectively to knock out new invasive species before they become a problem. Having fought the good fight, my advice about buckthorn is: be informed, be on the look out, and be proactive. There's also a super handy, targeted, and frugal way for homeowners and professionals to cut and treat buckthorn and other invasive shrubs. Appropriately enough, it's called a Buckthorn Blaster. 

How Water Striders Play With Light

It may have been the angle of light on the water, at that hour and in that season, but it was also the magic of multiple minds that caused me to pause long enough to see what I might otherwise have passed by. The minds were those of Mariah and her graduate student friends from the Princeton School of Public and International Affairs, who came three weeks ago to help at Herrontown Woods. After a midday workday, pulling some last remnants of stiltgrass along Barden pathways before their seeds dropped, we walked down to the stream. I wanted to tell them the story of the improbably large fish I had seen there back in April, but we soon focused in on something much more diminutive.

After a long late-summer drought that continued into fall, there was just enough water to host a gathering of water striders calmly zigzagging about on the waters's surface in the rocky stream. I pointed them out, thinking we'd note their novel buoyancy and move on. But the students took an interest, bent down to look more closely and, because they enjoy each other's company, began talking about what they were seeing. One observation led to another, and before I knew it, we began seeing aspects of the water striders we hadn't noticed before. What were those bright points of light where the striders' feet touch the water? And why did their tiny feet make such comparatively big shadows on the streambed?

It occurred to me that their feet make dimples in the water's surface that serve as tiny curved mirrors, reflecting focused light up towards us while casting shadows on the streambed. 

As with any natural phenomenon, the internet is packed with information to amaze and edify. AnimalScienceTV has an excellent video that lauds the water striders' quick reflexes and appetite for mosquito larvae. Water-phobic oily hairs help keep them high and dry. Water striders can be preyed on by an aquatic bug called a backswimmer, which looks like a water boatman. 

All this enlightenment began with an auspicious angle of light on the water, and a synergy of minds.

A Tour of My Backyard

My front and back yards were included in a Green Home and Garden Tour this past week. Organized by the Princeton Environmental Commission and Sustainable Princeton, the event packed into a Saturday tours of four gardens in town, plus tours of some very creatively designed homes.

In a 2023 video, the commission nicknamed my yard the Livestreaming Yard for all the strategies I've employed over the years to utilize stormwater runoff to feed a series of raingardens. 

I was feeling considerable trepidation in the weeks prior to the tour. Would any of the garden's late-summer glory linger through September? And there was a small matter of deferred maintenance, given that my passions and energies these days are mostly directed towards caring for Herrontown Woods. Back in 2017, my private yard had, in fact, served as the prototype for what evolved into the public Herrontown Woods Botanical Art Garden, or "Barden."

Throughout the week prior I methodically grappled with errant vines, cast truckloads of woodchip mulch over cardboard to suppress weeds, stacked firewood, reopened overgrown paths and thinned out volunteer trees--all the while feeling incredibly grateful that the fear of public humiliation was motivating me to do what should have been done long ago.

When the day of the tours arrived, the garden had regained a pleasing order, and a surprising number of wildflowers were still in bloom.

The twelve foot high Jerusalem artichokes--a native sunflower with showy flowers on top and tasty tubers underground--made good conversation pieces.

When not talking about the berms and miniponds that redirect or capture runoff to spare the house and feed the flowers, I sang the praises of stonecrop (Sedum spectabile), a nonnative whose flowerheads slowly transition from green to pink to burgundy to chocolate.

New England aster and panicled aster spoke for themselves,

while bumblebees crawled into the tubular turtlehead flowers to feed, or maybe take an early fall nap.

In late September, seedheads of ironweed, swamp mallow Hibiscus, and Joe-Pye-Weed can be nearly as ornamental as flowers.

The biggest hit, though, was the patch of pawpaws--a native fruit tree. Though in the same plant family--the Annonaceae--as tropical fruits like chirimoya and guanabana, the pawpaw is native to North America. Its custardy insides taste like a mix of mango and banana. 

What was not to be seen was as important as what could be seen. Through vigilance and early intervention, the yard has been spared the uber-weeds that plague many other yards--weeds like stiltgrass, lesser celandine, and mugwort. I've been less successful quelling creeping charlie, also known as ground ivy. 

And though there's been some toil over the years, there's been no pricetag, excepting a purchased shrub here and there. Many plants arrived in the form of seed collected from wild populations along the canal. Nature is generous, as are other gardeners one meets along the way, which was how I ended up with pawpaws.

Thanks to the organizers of the event and volunteers Mitch Jans and Per Kreipke, who helped sign people in throughout the afternoon. 

Fall Equinox Folk Festival at Herrontown Woods This Weekend

The Friends of Herrontown Woods is hosting a festival this weekend, on Sunday, Sept 21, from 3-5pm. The Chivalrous Crickets are returning, featuring the beautiful voices of sisters Fiona and Genevieve.

In addition to singing Celtic and other folk styles, they will also be leading some dancing. There will also be crafts, art, games, May's Cafe, and a raffle of an Einstein begonia. Tickets available at the link.

Check out a video of the Crickets:

Late-Summer Joys Large and Small at the Barden

The Barden is the nickname for Princeton's Botanical ARt garDEN: 160+ native plant species informally gathered along whimsical pathways next to the main parking lot at Herrontown Woods, 600 Snowden Ave. By combining the signage with a cellphone app like Seek, you can use the Barden for one-stop learning of local flora. 

One of my annual joys at the Barden is getting to show kids and adults the exploding seeds of jewelweed, which has lately been producing beautiful tubular orange flowers that segue into pods with spring-loaded seeds. Find a swollen pod, pluck it gently from the plant, put it in the palm of a kid's hand and let them touch it lightly with a finger of the other hand. Kabloosh! The seeds go flying. It is really hard not to feel surprise and delight, no matter how many times you've witnessed this.  

An unexpected opportunity to share this experience came this past Sunday morning. We showed up to host our monthly pop up May's Cafe at 9am only to find the parking lot already full. Turned out that Cub Scout Pack 98 had driven down from Kendall Park for a two mile hike in the woods. 

When they returned from the trails, I showed them the exploding seeds, 

and also introduced them to the charismatic green frog that calls a little round minipond home, near the kiosk. Though the natural vernal pools have dried up in the late summer's long drought, we have a number of frogs participating in our Barden frog-in-residence program, which consists of a few plastic lined miniponds. 

Other joys are of the botanical variety, and probably wouldn't have held the scouts' attention like the frogs, but here they are in photo form. 

Two or three years ago, friend Stan gave me some little plants he had grown from seed. Among them was showy goldenrod--a kind of goldenrod I remember from Michigan as a beautiful accent in prairies, but had not seen in NJ. It makes long spires of yellow and, most endearingly, doesn't spread aggressively underground like some of the other goldenrods. This is the first year it has bloomed in the Barden.

When late summer meets early autumn, black gum leads the way with its brilliant red leaves.

This staghorn sumac looks a bit like a painted vulture drying its outstretched wings.

Woolgrass is not a grass, so let's call it woolsedge, Scirpus cyperinus. Admire its elegant seedhead, and feel its triangular stem that, like papyrus, prompts us to proclaim "sedges have edges." 

Very thoughtful of Autumn Helenium to wait until now to bloom. 

It's been a great year for ironweed, the relatively cool weather having extended its bloom.

I think of evening primrose as blooming through the summer, but didn't notice it until now, for some reason.

Our native euonymus, Strawberry bush, is developing its fruit, which will burst open later, revealing bright orange berries.

Late-flowering thoroughwort can look elegant or weedy. This year, perhaps due to the cooler weather, it has looked elegant, attracting many pollinators and exuding a wonderful honey-like fragrance.

Pokeweed, too, combines elements of elegance and weediness. The pendulant berries and bright red stems are attractive, but the leaves are a decadent jumble.

An unexpected delight this year was a plant that decided to grow near the gazebo. 

The name, rattlesnake root, Nabalus altissimus, doesn't capture the beauty of the pendulant flowers, each opening in turn, attracting a crowd of green/gold bees. 

Thanks to my entomologist friend David Cappaert, who quickly offered a name and a detailed closeup of the little bees--"one of the 'green halictids,' a set of several genera with green-gold coloration. They can be hyper-abundant at this time of year. Image here is of one in hibernation – you can find these under logs in the winter."

The show of asters has begun with woodland aster. Summer is not done yet!

You can visit the award-winning Barden any time, by driving down the lane across Snowden Lane from the Smoyer Park entrance. Say hello to the frogs, play a game of chess, or bring a lunch to eat in the gazebo. The address is 600 Snowden Lane, and we generally host a May's Cafe from 9-11 on first Sunday's of the month. Check HerrontownWoods.org for details.