Maintenance Will Determine the Fate of the Betsey Stockton Garden

When I look at a plant, a garden, a meadow, a forest, I can see the future. It's a form of extrapolation, defined in the Oxford Dictionary as "the action of estimating or concluding something by assuming that existing trends will continue." I only realize now, writing this, that not everyone exercises such powers. Not everyone has been a gardener of landscapes for fifty some years, accumulating memories of myriad plant species and observing their behaviors. I've seen thriving raingardens and neglected ones, healthy meadows and forests, and degraded ones. I've observed how various invasive weeds spread and come to dominate, each in its own manner and at its own pace. These are the accumulated data points used to predict the future.

One very satisfying thing about extrapolation is that I can see, in my mind, the flower a bud will become. But with that same power to see a garden blooming while still in bud, I can look at a garden in what for others is glorious bloom and see the "seeds" of ruin--the scattered pockets of invasive mugwort, nutsedge, stiltgrass or lesser celandine, crown vetch or Chinese bushclover that without early intervention will quickly expand and ultimately prevail. 

My interventions--a broad mix of successes and failures--have taught me above all that early intervention can make the difference between hope and despair. 

One special garden in town that I stop by to check up on, like an old friend, is the Betsey Stockton Garden planted atop the Firestone Library at Princeton University. This is a complex native planting, containing 35 native grassland species. The person or crew maintaining the garden needs to be able to recognize and identify all 35 intended species, plus all the weeds that could potentially cause problems, not only when they're blooming but at all stages of development. 

That deep knowledge is a tall order. Knowing how little respect maintenance often gets, I worry about this meadow garden in the longterm. Will it receive the knowledgeable, strategic attention it needs to thrive? This photo of wild bergamot blooming with lots of clumping goldenrods suggests things are going well. 

Here, some black-eyed susans lend color, but the pink blooms of quickly spreading non-native crown vetch spell trouble.

New to me is a weed called rabbits foot clover, which may have hitchhiked in from whatever distant nursery the intended plants came from. This, too, was not caught early, and now poses a significant challenge.

Thankfully, there's only one small patch of the fearsome mugwort, but that could quickly expand if not dealt with quickly. Getting as close to zero tolerance for invasives as possible makes maintenance much easier. 

Maintenance is not given its due in part because success is often invisible. In a house, we note dirt's presence, not its absence. A well-run government agency doesn't make it into the news. The bass player who provides the harmonic foundation for a band often goes unnoticed until he plays a wrong note. In medicine, catching problems early doesn't pay as well as dramatically rescuing someone whose problem has grown into an emergency. Extrapolation can help with this. It allows us to see large consequence in small acts, to appreciate how big a problem has been avoided by digging up a small, isolated patch of mugwort.

I found a few relevant local writings. One was an opinion piece in the Daily Princetonian by an undergrad, calling for more native plantings on campus. Planting is a good start, but what goes unmentioned in the opinion piece is that maintenance determines any planting's fate. 

One strategy being used in newer native plantings on campus is to plant gardens with only three or four species, with lots of mulch inbetween plants. This reduces the amount of training required for maintenance. 

Other local writing specifically about the Betsey Stockton Garden can be found in the Princeton Magazine. It includes the list of intended plants (below), and describes the garden as low-maintenance, but that assumes the invasive weeds will be caught early and removed before they can spread.

The Betsey Stockton Garden was planted in 2018, two years after the demise of another campus native planting, around the Neuroscience Institute. Hopefully some lessons are being learned, and the University will bring the necessary expertise and strategic timing for maintenance to bear on this lovely, botanically complex planting. 

Native Plants Featured in the Betsey Stockton Garden
(Some are used on the High Line as well.)

Grasses: Carex comosa, Appalachian Sedge Carex pensylvanica, Pennsylvania Sedge Festuca ovina, Sheep’s Fescue Festuca rubra, Creeping Red Fescue Sporobolus heterolepis, Prarie Dropseed Elymus virginicus, Virginia Wild Rye Schizachyrium scoparium, Little Bluestem Tridens flavus, Purple Top Shade Plants: Aqueligia canadensis, Wild Columbine Aster laevis, Smooth Blue Aster Blephilia ciliata, Downy Wood Mint Erigeron puchellus, Robin’s Plantain Eurybia divaricata, White Wood Aster Polemonium reptans, Jacob’s Ladder Sisyrinchium angustifolium, Narrow Leafed Blue-Eyed Grass Solidago caesia, Blue-stem Goldenrod Solidago flexicaulis, Zig-Zag Goldenrod

Full-Sun Plants: Asclepias tuberosa, Butterfly Milkweed Aster laevis, Smooth Blue Aster Aster pilosus, Heath Aster Baptisia alba, White Wild Indigo Baptisia perfoliata, Catbells Centaurea cyanus, Cornflower Chamacaesta fasciculata, Partridge Pea Coreopsis lancelota, Lanceleaf CoreopsisEchinacea pallida, Pale Purple Coneflower Echinacea purpurea, Purple Coneflower Monarda fistulosa, Wild Bergamot Penstemon digitalis, Beard Tongue Rudbeckia hirta, Blackeyed Susan Solidago juncea, Early Goldenrod

Persistence Furthers With Garlic Mustard

Another weed that is risky to let get established in your yard is garlic mustard. The plant shoots up 1-3 feet high during its second year, and is easy to spot right now with its cluster of little white flowers.  The flowers look decent enough, but a laissez faire approach will lead to this weed taking over, altering soil chemistry and crowding out other flowers. The garlicky smelling leaves are edible, especially when young, but you'll never eat enough to control it. 

The strategy for combatting aggressive plants in the garden is different for each species. Garlic mustard is a biennial, meaning it gathers energy the first year, then blooms and dies the second year. If you leave it while it's flowering, chances are you'll forget to pull it later, after it has blended back into the green of the garden. By the time the plant dies and turns brown later in the summer, marring your garden with its skeletal remains, the seeds will have matured and dispersed, creating an even bigger problem next year. 

But foil its attempt to make and spread new seed, and the soil will eventually run out of seed to make new plants. Best to pull now, while in bloom, though it can be pulled any time before the seeds mature. "Grab low and pull slow" is a good motto for getting as much of the root as possible. Don't put the pulled plants in your compost pile. Even when pulled while young, there's still a chance that the flowers will mature into viable seed. 

To avoid having to stuff the pulled plants in trash bags to send to the landfill, what we've done at Herrontown Woods is pull every last one we can find, then pile them in an out of the way spot, so that any seeds that mature on the pulled plants and sprout the next year will be easy to find and pull. Pulling gets easier each year, until what once took hours now takes but a few minutes. 

All problems should yield so nicely to persistence. 

Related posts: 

• Girlscouts make quick work of garlic mustard at Herrontown Woods
• A Garlic Mustard Success Story from Michigan

Lawn Blotch 2024

Maybe people have another name for it, but every April there is a condition of some lawns that catches the eye. I call it "lawn blotch," which develops early in spring when the grass has yet to grow but other plants have.

Those other plants that spring forth here and there in a lawn might be Star of Bethlehem, which will later have pretty white flowers but spreads underground, popping up all over the place in your yard. 

Or they might be the pretty but terribly invasive lesser celandine,  which will become a nuisance for you, your neighbors, and your local nature preserve if you don't spray it or dig it up.

Or they could be a weedy allium that I call wild garlic. 

None of these plant species are native. Lesser celandine is poisonous. 

Lawn blotch has at least one positive, though. I've frequently seen the wild garlic being gratefully harvested by people of Asian heritage, to use in cooking like chives or onions. 

Lawn blotch as a phenomenon quickly passes, as the weather warms and the grass begins to grow, and lawn mowers once again impose a vertical conformity on the suburban landscape.

As an adendum, below is a fun quote from a post I wrote about lawn blotch eleven years ago. Though the climate has been changing considerably, lawn blotch still coincides with the Masters golf tournament: 

"As master golfers stride the perfectly groomed grounds of Augusta National this weekend, showing their mastery over a landscape that's kept in a perpetual state of arrested development, let us glance out the window for a moment at the less applauded realities of the suburban lawn. In the Masters tournament, only the hazards--the trees and shrubs--are allowed to reach maturity. For the golfer, any encounter with interesting plants is a sign of trouble. And in the yard, the main threat to calm conformity is the plant that seeks to lead a full life, by flowering and maturing its seed. (Full disclosure: I lettered in golf in high school, spent part of a summer mowing fairways, and probably developed a keen eye for plants while searching for lost balls in the nearby corn fields and the very rough rough of our neighborhood's rough-hewn golf course.)"

Lesser Celandine Spreading Into Local Parks

Poisonous to wildlife, crowding out other plants, be they native wildflowers or turfgrass, lesser celandine spreads across sunny lawns and shady forests alike, forming dense, exclusionary mats that can extend far into the distance. 

I've written many posts about this highly invasive plant, and how it can be controlled with targeted, minimalist use of herbicide if one catches it early in one's yard or in a local park or preserve. Invasions start with one isolated plant like this, which can be easily sprayed with systemic herbicide without damaging nearby vegetation. (Or dug up and thrown in the trash, not the compost.) Of course, one plant looks harmless enough, but its rapid spread will change your view from "Gee, that's pretty" to "Help!!"

Incredibly, this spring I happened upon a homeowner in our neighborhood who actively sells lesser celandine and other plants she digs from her garden, apparently via facebook marketplace. Her garden is infested with the plant, and so this noxious weed will hitchhike in the soil of any garden flower she sells. Though it has a pretty flower, it's rapid spread will cause gardeners to lose control of their gardens, and to then serve as vectors for the plant's additional spread to neighboring lands. I asked the woman about the ethics of selling and intentionally spreading such an invasive species, and she refused to even discuss it. She blamed her unreceptivity on someone who had confronted her about it in an unfriendly manner. I asked "What if a nice person were to raise the issue with you?" But she still refused any discussion.

I may be having more success with Princeton parks. This spring, a friend, Mimi, was concerned about the status of the London plane trees along the Scott and Hella McVay Poetry Trail in Greenway Meadows, and asked me to take a look. The trees definitely need some attention, given all the invasive shrubs growing beneath them, but I also noticed that lesser celandine is beginning to spread through the park's meadow and lawn. 

Here's that classic "first plant" which would ultimately carpet the whole meadow with its poisonous foliage if not treated. 

And here's an early infestation in the lawn that extends down to the ballfields and into the land surrounding the DR Greenway Johnson Center.

I urged the town to take action, and it appears they will. 

This spring has not been ideal for spraying lesser celandine. Days have remained cool, which I personally like, but it's best for the temperature to reach 50 degrees for effective treatment. Of course, having just written that, I come upon a source that says at least 40 degrees. 

Glyphosate--much vilified for its overuse in agriculture--is still the most dependable systemic herbicide to use. If close to wetlands, a wetland-safe formulation (not Roundup) can be used, though it takes some sleuthing on the internet to find it. For foliage, a 2% solution is good, but some use 4%. 

I've heard that some land managers use an herbicide called Milestone, which may be a useful alternative, particularly because it doesn't harm surrounding grasses. 

If you read online about lesser celandine, you'll sometimes see claims that it must be sprayed very early in spring, before it flowers. Early spraying in helpful, but people should not be deterred from spraying later in spring as well. You'll also see claims that lesser celandine might be mistaken for the native marsh marigold. But marsh marigold is extremely rare. In all my explorations of Princeton's open space, the only marsh marigolds I've seen are the few that I have planted. 

Lesser celandine reminds us that we are all connected. What one person allows to grow in the yard can impact neighbors and nearby natural areas. The more a neighborhood becomes infested, the more likely it will spread to your own yard, through landscapers' mowers or on the hooves of deer. Thus, one person's problem quickly becomes other people's problem. It's important to be vigilant. 

Last Chance to Pull Stiltgrass -- 2023

This week and maybe next are your last chance this year to pull stiltgrass (Microstegium vimineum). This mega-invasive is an annual, so the logic of countering its spread is to pull it before it can produce and drop seed. If the seeds haven't loosened yet at the end of the stalk, you can still pull it. Throw it in the trash, or if there's a lot, make a big pile of it so that any seeds that sprout the next year will all be in one place and easily covered or pulled. Definitely don't put it in your compost if its seeds are forming. If stiltgrass is just starting to invade your yard, pulling as completely as possible now will greatly limit its seedbank for next spring. Another strategy for large stands is to let the stiltgrass grow, then just as it begins to flower mow it short and hope its feeble roots don't have enough energy to grow another flowering stalk. 

For those fuzzy on identification, google lots of images, and look for the silver line running down the middle of the leaf. Stiltgrass can grow in the shade or sun, climb up to four feet, or thrive in a miniature state while ducking below your mower in the lawn. It's incredible survival skills include being incredibly inedible for wildlife. Stiltgrass gives nothing back to the habitats it increasingly dominates.

More on Stiltgrass, and a Success Story

Walking in the local woods, you've probably seen this kind of scene--what looks like a grassy meadow extending through the forest. In the filtered light of the understory, its simplicity and lushness may have some visual appeal. And yet, in some ways what you are looking at is the ecological equivalent of an urban food desert. 

Stiltgrass is an introduced plant that could be called a pervasive invasive, able to thrive most anywhere and dominate whole landscapes. Its success has come in part through being inedible. As wildlife selectively eat native vegetation, the stiltgrass expands, preventing the native plants from rebounding.

Unlike another nonnative annual weed that can look similar, crabgrass, stiltgrass becomes ubiquitous because it can thrive in sun or shade. That means the stiltgrass invading your lawn and flower beds can continue spreading ad nauseum into the nearby forest, or vice versa.

We used to call it bamboo grass--something in the shape of the leaves is reminiscent. The stiltgrass name refers to its angular growth, with each segment supporting the next as it climbs up and over fallen logs and other plants. Packing grass is another common name, referring to how it was once used to pack porcelain for shipment. That's probably how it first reached the U.S., in packing crates sent to Tennessee. 

When I first encountered it, growing on the bank of Ellerbe Creek in Durham, NC, I thought it graceful. Then came Hurricane Fran, bringing floods and fallen trees. In the aftermath of that massive disturbance, stiltgrass exploded in the landscape, expanding and ultimately choking forests with its vast, dense stands. New Jersey proved no different. 

Stiltgrass tends to establish itself along roadsides. Here it is growing in a green ribbon along Herrontown Road. Trails, too, provide an avenue for extending its reach, its tiny seeds carried on boots or the hooves of deer.

Though stiltgrass has covered large areas of woodland in the eastern U.S., we have found it worthwhile and even satisfying to counter its relentless incursions. Today in the Barden at Herrontown Woods, some volunteers pulled it out of a patch of native jewelweed along the edge of the parking lot. 

Nearby, on land where we have largely eliminated a massive clone of wisteria, stiltgrass was starting to move into the void. If nothing were done, this open woodland would have become a pasture of stiltgrass. But we have acted early enough to be able to remove all of this year's stiltgrass, dramatically reducing the seeds available for next year's crop. This photo shows the last patch before we pulled it. 

Interestingly, there are native grasses that look a little like stiltgrass, the main one being Virginia cutgrass (white grass), Leersia virginica. It has longer, narrower leaves that lack the silver stripe down the middle. As is a common ecological refrain, the native grasses "play well with others," not forming stiltgrass's massive, exclusionary stands. Some smartweeds like Lady's Thumb can also bear a resemblance. 

The Invasive Grass Fueling Wildfires in Hawaii

Hawaii didn't used to get pummeled by highly destructive wildfires. What has changed? A big part of the answer lies in the interaction between climate change and invasive species. 

Begin with a couple paragraphs buried in a NY Times article:

The area burned annually by wildfires in Hawaii has quadrupled in recent decades. Declining rainfall and rising temperatures have left the islands more susceptible to blazes, climatologists say.

Invasive grasses that are highly flammable have crowded out native vegetation in some areas, and climate change has exacerbated dry and hot conditions in the state, allowing wildfires to spread more quickly.

But what invasive species? A University of Hawaii website points to one that has been particularly destructive:

Guinea grass (Megathyrsus maximus), a nonnative invasive grass in Hawaii, forms dense stands that outcompete native plants and has very high fine fuel loads that greatly increase fire potential, spread, and severity.

Wikipedia describes guinea grass as a tough customer, growing ten feet tall. Though it can thrive in full sun, it can also tolerate shade, allowing it to invade native woodlands and thereby increase their vulnerability to fire during droughts. Native to Africa, the grass was introduced not only to Hawaii but also to south Texas.

How did guinea grass get to Hawaii (also spelled Hawai'i)? Wired provides an answer:

When Europeans arrived in the late 18th century and established plantations for growing sugarcane and pineapple, they also brought invasive grasses. Now the economics have changed, and those fields lie fallow. But the grasses have spread like a plague. “Those fire-prone invasive species fill in any gaps anywhere else—roadsides, in between communities, in between people’s homes, all over the place,” says Pickett. “At this point, 26 percent of our state is covered in these fire-prone grasses.”

This stuff is highly sensitive to short-term fluctuations in rainfall. The grass will grow like crazy when the rains come, then quickly desiccate when the landscape dries. “When we get these events like we’re seeing these past few days—when the relative humidity really drops low—all those fine fuels become very explosive,” says fire ecologist Clay Trauernicht of the University of Hawaiʻi at Mānoa.

An article in ABC News explains how the more intense and frequent fires affect the soil and human health: 

Elizabeth Pickett, co-executive director of the Hawaii Wildfire Management Organization, a nonprofit working with communities to prevent and mitigate fires, lamented the changes wrought by fire.

Invasive and fire-prone grass species have moved in over time and during a fire they can burn into native forests, which means the forests are replaced by more grass, Pickett said. The soil burns and sloughs off, leading to massive post-fire erosion that smothers coral, impacts fisheries and reduces the quality of the ocean water, she said.

The state is windy and the dust blows for years, harming human health, she added.

“When you lose your soil, it’s really hard to restore and replant. And then the only thing that can really handle living there in many cases are more of those invasive species,” Pickett said. “It’s systemic. Air, land and water are all impacted.”

A Philosophical Footnote

It's important to note that both climate change and the spread of invasive species are largely unintentional. Our world is threatened by excess carbon dioxide and other planet-heating gasses--lowly biproducts of our economy and lifestyles. We are used to thinking of collateral damage as minor and incidental, and tend not to judge people by what they do unintentionally. In fact, the cumulative impact of unintentional acts is the central threat we face. We live our days trapped in a predicament in which humanity, largely well-meaning, is allowed to collectively and unintentionally create problems, but not allowed to collectively and intentionally solve them. 

Additional reading: Thanks to a comment (see the critical comment and my response below), I found a couple more interesting articles about guinea grass. One gives a good overview of guinea grass as both an excellent, deeply rooted forage grass for cattle, and a weed that has disrupted ecosystems and croplands around the world. The other invests the grass with cultural connotations.

Other Invasive Grasses Fueling Fires in Hawaii

My friend Fairfax sent a link to another informative article that mentions three other introduced grass species fueling fires in Hawaii: fountain grass, buffel grass, and molasses grass. It also stresses that these and other highly flammable introduced grasses are altering fire ecology in the mainland U.S. as well.

What Guinea Grass Has in Common With Japanese Stiltgrass

Some people aren't aware the extent to which grasses affect our lives, for better and for worse. Corn is a grass, as are sugar cane, bamboo, and sorghum. In Princeton and up and down the east coast, the most dominant invasive grass is Japanese stiltgrass, which like guinea grass can grow in sun or shade, and uses what's called C4 photosynthesis to fix carbon from the atmosphere. Plants that use the C4 process--corn also being an example--are more efficient than other plants that use C3. Stiltgrass has invaded most areas of Princeton, growing from a zillion seeds each spring to blanket large expanses of woods. Wildlife don't eat it, so as it takes over, the landscape becomes increasingly inedible. I've long wished that someone would come up with a highly selective herbicide that would impact only C4 plants. If stiltgrass's impact on eastern habitats hasn't been sufficient to stimulate research, maybe the fire hazard in Hawaii will get researches to take a look.

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. 

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. 

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

Wisteria Contained

As a land manager, having fought back many a runaway acre of wisteria in a woods, tangled with and been tripped up by its myriad tanglings, even walked upon the tranpoline-like, crazy quilt its runners can weave above the ground, I can still feel amazement when witnessing a wisteria molded by intention--first at its abundant flowering, and second, that someone has managed to keep its wanderlust in check. 

This house is a couple doors up from Hamilton Ave. on Linden Lane. Similar displays are likely in progress on the front porch of Morven and at Marquand Arboretum. They hearken back to an era when people had the time and interest to tend to their gardens, when gardening was a relationship, and gardens had personalities. My parents had such a garden in Ann Arbor, MI, where I would trim the wisteria growing up their patio trellis. The flowers were pretty, but never reached the magnificence of this display on Linden Lane.

The wisteria in this photo is thankfully in the front yard, along a town street. If the owner ever lost interest in carefully maintaining it, there's no nature preserve nearby for the wisteria to swallow, only the house and the neighbors' yards. Having witnessed and reckoned with the unintended consequences of inattention, I can see both the beauty and the Burmese python-like potential lurking within, its expansionist nature for now contained.

Related posts:

Where Vines Tackle Trees: A wisteria that grew so thick you could walk on its web of runners without touching the ground. 

Another Perilous Embrace--Wisteria and Horse Chestnut: When wisteria gets loose in a neighbor's yard.

Lesser Celandine Alert!

It's time for the annual call to action to prevent lesser celandine from taking over all of Princeton. Also called fig buttercup, it's a highly invasive nonnative plant that is spreading rapidly, yard to yard and into parks and nature preserves, where it degrades habitat for wildlife. It thrives on homeowners' indifference and inaction, so I've been doing what I can, urging town officials to defend our parks and preserves, urging homeowners to take action in their own yards, explaining that herbicides are not anti-nature if they are used selectively and medicinally. My letter to the Town Topics and other local publications starts like this:

Blooming in many people’s yards right now is a small yellow flower that, upon closer inspection, proves not to be a dandelion. Variously called lesser celandine or fig buttercup, its radical invasiveness triggers a predictable progression of emotions in the homeowner. Delight at its pretty flower soon turns to alarm as year by year it takes over the yard, spreading through flower beds, across lawns and into neighboring properties. What may start as a few scattered, harmless-seeming clumps quickly becomes the equivalent of a rash upon the landscape. Unlike the dandelion, lesser celandine also spreads into nature preserves. Poisonous to wildlife, it forms thick stands reminiscent of pavement. Over time, our nature preserves become less and less edible to the wildlife they were meant to support. Native diversity shifts towards non-native monoculture.

Below are some photos to help with identification, and here is a link that includes suggested means of stopping it from taking over your yard. Though the link says only to spray through early April, I'd suggest that spraying is helpful for as long as its leaves are green. Lesser celandine is a spring ephemeral, meaning that it comes up early, then dies back in June, going dormant until the next spring. Gardeners who like to dig up plants of this or that to give to friends should be aware that, if their yards have been invaded by lesser celandine, some of it may hitchhike in whatever plants they dig up later in the season to give away. They may unwittingly be giving a fellow gardener the beginnings of a major headache.

Lesser celandine is poisonous, and yet some websites declare it edible and offer recipes. Why the contradiction? Apparently, lesser celandine accumulates toxins later in the spring. The toxins break down during cooking or after drying. Still, one takes one's chances trying to eat it, and, alas, wildlife don't cook.

I've seen bees collecting pollen and nectar from the flowers, which is all fine and good, but this doesn't compensate for the inedibility of the leaves. The invasion of our lands by nonnative plants that wildlife don't eat essentially shrinks the acreage of functional habitat in Princeton, even though a great deal of open space has been preserved. Thus the need for management.

Given that some areas of Princeton have been overrun by lesser celandine, it's important to defend those areas that have not, by closely monitoring and spot spraying where the plant is just starting to move in. Invasions begin with just a few plants here and there. An absolute minimum of herbicide is needed to easily defend these areas. Lesser celandine can easily be distinguished from dandelion. Walk the grounds before the grass gets mowed in the spring and while the plant is blooming. For lawns, a product like Weed B Gone works. For other areas, a 2% solution of glyphosate does the trick. Since glyphosate can take a week to show visible effect on the plant, it's best to spray early in the spring so that there's time to see results and spray any areas missed. For those near wetlands, wetland-safe formulations of glyphosate are available, so Roundup is not the only option.

In terms of aesthetics, lesser celandine's dense, exclusionary growth does to the landscape what people badly afflicted with narcissism do to social situations. A woodland that once hosted a diversity of native wildflowers becomes, when overwhelmed by lesser celandine, one species' declaration of Me! Me! Me! 

Here's what it looks like up close.

Here's an example of the blotchy appearance an early invasion creates on a lawn. These blotches expand until the whole yard is coated.

The closest lookalike in the lawn is the violet, whose leaves are darker, more curled, and more toothed along the edges. 

Mile-a-Minute Spreading into Princeton

 One of the more noxious invasive plants that has been spreading across NJ is Mile-a-Minute. It's a prickly vine that, though an annual that must grow back from seed each spring, grows so fast that it can cover large areas of roadsides and field edges. Over the past several years, I've been knocking out small infestations at the Princeton Battlefield and near Rogers Refuge, but this year I'm finding new patches springing up around town.

Then, driving my daughter to MarketFair along Canal Pointe Blvd a week ago, I saw a massive infestation that surely is a major source of the seeds that birds are then spreading across Princeton. 

The vine has a distinctive triangular leaf. Berries are just beginning to ripen. If you encounter it, put some gloves on, pull it out and put it in the trash. Putting it in the compost would allow the seeds to spread. 

The infestation along Canal Pointe Blvd is behind 701 Carnegie Center Drive. In the aerial, you can see rows of solar panels over the parking lot. To the left of the solar panels is a big mowed lawn, and to the left of the lawn in the photo is the unmowed land upon which the Mile a Minute is growing. My friend Peter researched the owner, which on the deed appears to be "BXP Carnegie Owner, LLC%G". The land has a farm easement, so is only valued at $39,000, which means the owner is paying next to no taxes to hold very valuable property, meanwhile expediting the spread of Mile a Minute and the associated nuisance it will cause. 

It's hard to photograph the cocktail of invasive species at the site. The white flowers are of white snakeroot, a native wildflower, which is besieged by a layer cake of stiltgrass, porcelainberry, and Mile a Minute climbing on top of it all. 

Further down the road is a series of trees damaged, perhaps by a small tornado or similar localized intense winds as the remains of Hurricane Ida came through on Sept. 1. Similar damage to trees was seen in Princeton Battlefield, where a row of mature white pines along the edge of the field was decapitated.

What we're seeing is the increasing impact of plants out of place (species that turn invasive after being introduced from other continents) and carbon out of place (carbon fuels extracted from underground that we burn, thereby releasing additional carbon dioxide into the atmosphere). Our machines have increased global warming CO2 by a whopping 50% over pre-industrial levels thus far. This year has felt like a radicalization of both invasive species and climate change. 

Butler Tract Meadows Restoration?

This is the story of what can go wrong if you plant a native meadow and then don't take care of it. Princeton University has been installing some native meadows, and some have done a lot better than others.

Just off of South Harrison Street, framed by Sycamore Rd and Hartley Ave, are some meadows that were planted in 2016 following the university's demolition of the Butler apartments. It was a well intended succession from graduate housing to native meadow, and when I took a look in 2019, the meadows were still hosting diverse native wildflowers. 

Two years later, these signs appeared: 

"Butler Tract Meadows is under an invasive management program for this year."

For most of the summer, it wasn't clear what that meant. The signs appeared early in the growing season, but I could find no sign of any action. 

 

This photo tells the story of what happened to the native meadow over the course of five years. The usual nonnative invasive species moved in and began to dominate, with mugwort foremost among them. The white flowering plant on the left is Japanese knotweed, which can form large monocultures as well. Bamboo is getting a foothold in the lower lefthand corner of the photo, and in the distance can be seen the sproutings of black locust, a native tree that nonetheless can move aggressively into native grasslands. 

Sericea lespedeza (L. cuneata) is another super-aggressive nonnative. Newer on the Princeton scene, it can rival mugwort in its capacity to displace diverse native plants, for instance along the gasline right of way that crosses the Princeton Ridge. 

And here's crown vetch, which climbs over everything around it. Both crown vetch and Sericea lespedeza were planted extensively along freeways to control soil erosion, reducing one environmental harm while creating another. 

I did notice a few native species still present, including this wild senna. The only practical means of shifting the balance back to the native species on this scale is through use of herbicides. Some people lump all herbicides together and pronounce them evil poisons--an indiscriminate rejection borne of their often indiscriminate use. But there are many kinds and many formulations, some far safer than others, and the aim as with medicines for people is to use as little as possible, in a targeted way. 

The way to reduce the use of herbicides is to be proactive and intervene early to kill the invasives when they are still few in number. That would have been something to do from the beginning, back when a more targeted, minimalist approach was possible. 

My friend Basha who lives across from the Butler Tract told me they had finally done some spraying. A week later, I took a look. Here you can see the black locust tree sprouts turning brown while many other invasive plants appear untouched.

This big patch of mugwort shows some sign of dieback, but pretty uneven results thus far.

I'm guessing that patch in the background of this photo was crown vetch. In the foreground is probably common cinquefoil (Potentilla simplex), which is native but a very rapid spreader.

It will be interesting to see how this goes. My experience is that institutions have always understood that lawns and landscaping take ongoing care, but they have yet to grasp that more naturalistic areas like meadows also need ongoing intervention. At the Butler Tract, they seem to be trying to figure out what that means.