Invasive Plant Species in Princeton

This Monday, May 22 at 7pm, the Princeton Public Library will host a presentation on invasive species in Princeton by Mike van Clef, of the NJ Invasive Species Strike Team. There will also be representatives of FOPOS and DR Greenway participating. Princeton municipality hired Mike to develop a report on invasive species in Princeton preserves, and in 2016 he and two interns worked through the summer on invasive species control. Because of the massiveness of the problem, they focused on emerging species--those whose populations are still small enough that a summer's worth of control would make a difference. 

We may look back on 2016 as a pivotal year, when the town began investing in invasive species management, much as 2000 marked the beginning of professional deer management in town. 

Although it may sound self-congratulatory, another important date in Princeton's history of invasive species management would be 2006, when the Friends of Princeton Open Space hired me as their first Natural Resources Manager. 

When I arrived in town in 2003 on the coattails of my wife's appointment to the Princeton University faculty, a couple things quickly became obvious. First, Princeton had done wonderful work preserving land for open space. Second, the open space itself needed a lot of work. Though the trees in Princeton's woodlands were mostly native, the understory vegetation was often dominated by nonnative, invasive plants. Stiltgrass, honeysuckle and privet, to name but a few, had filled the void created long ago when the diverse native understory had been plowed under, back in Princeton's agricultural era. In the decades since, the native trees had rebounded, but the understory had either not come back, or succumbed to heavy browsing pressure from deer.

Because wildlife tend not to eat the leaves of nonnative plants, their proliferation in preserves renders the habitat largely inedible. Yes, birds can eat the berries of nonnative shrubs like honeysuckle, but if the insects and other wildlife aren't eating the leaves, then much less of the solar energy captured in the plants can move up the food chain. 

I proceeded to make the case that Princeton could expand its effective acreage of open space through management for native species. As most readers know, I've been leading workdays and nature walks ever since, for six years as an employee of FOPOS, and more recently as president of the Friends of Herrontown Woods (FOHW). Highly motivated volunteers like Tim Patrick-Miller and Andrew Thornton, and more recently Kurt and Sally Tazelaar at Herrontown Woods, have had a positive impact over time. Meanwhile, FOPOS has sustained its Natural Resources Manager position--having just hired the fourth to hold that position--and continues to do invasive species removal at Mountain Lakes Preserve. After so many years of nonprofit, largely volunteer efforts, to finally get municipal support through Mike's crew this past summer was a real boost that we hope will continue.  

It's important to note that Mike van Clef's study of invasive species in Princeton is limited to parks and preserves owned or managed by the town. There are large expanses of open space owned by the state (Princeton Battlefield and DR Canal) and by the Institute for Advanced Study (the 600 acre Institute Woods). Portions of the Battlefield and the DR Canal are being overrun by porcelainberry (in photo), which barely registers in Mike's survey, and mile-a-minute vine is beginning to show up there as well. I've been trying to help fill a void in management, co-leading workdays at the Battlefield and, in the proactive "early detection, rapid response" tradition, dealing with two small infestations of Mile-a-Minute in town before they become unmanageable. Another nonnative plant that's spreading rapidly, both in people's yards and in nature preserves, is lesser celandine (a.k.a. fig buttercup). It can only be controlled in the spring, long before summer interns begin work. Ideally, a town-wide coordination to manage invasive species would be developed.

The town's investment in invasive species control comes at a critical time. With the emerald ash borer (another highly invasive introduced species) poised to decimate Princeton's most numerous native tree, large gaps will be created in our forest canopy, allowing light to penetrate to the understory. Princeton's long investment in deer culling has allowed native shrubs like spicebush to make a comeback, but in many woodlands, the understory is dominated by nonnative shrubs and stiltgrass. Wildlife have evolved over millenia to eat native species. It's a question of whether edible natives will capture that extra sunlight in the understory, or the privet, winged euonymus, honeysuckle, barberry and Photinia. The foodchain depends on our intervention.

The primary argument for habitat management remains that, by improving the quality of habitat, Princeton effectively increases the functional acreage of open space. This is true not only for wildlife but also for people. Controlling invasive species also makes the human experience in preserves more rewarding. As we've cut down invasive shrubs at Herrontown Woods, we've not only made more sunlight, water and nutrients available for native species to prosper, but also have opened up pleasing vistas and made the woods more navigable. 

The problem of invasive plants may seem overwhelming, but we can take our inspiration from the deer, who transform landscapes through the cumulative impact of browsing here, there, and everywhere, one mouthful at a time. The pioneers, too, thought the continent too vast to ever tame. Though their goal wasn't exactly to increase native plant diversity, they showed how steady effort makes a difference over time. Ideally, professionals will complement existing volunteer efforts, and the locals who know the preserves best will help steer the professionals' interventions. 


At Monday's presentation, there will also be discussion of a list of invasive species that people are being discouraged from planting. It's a very long list, and I wish it could better reflect the broad spectrum of invasive behavior we see in the field. One reason the list is so long is that, though many of the species on the list may not be found spreading into Princeton's nature preserves, history shows that invasive behavior in nonnative species may not become manifest until many decades after they've been introduced. Chinese silver grass (Miscanthus sinensis) is a case in point. Though it has yet to spread to Princeton's Tusculum meadows, it is now posing a big problem for meadows at Duke Farms up in Hillsborough. The flyer for the library event includes a photo of butterfly bush, which I've never observed exhibiting invasive behavior. Monday's presentation may help put local observations in a broader context.

Update: Full house for the program! Good to see.

Winter Aconite and Fig Buttercup (lesser celandine)--Related Flowers, Contrasting Behaviors

Both of these non-native wildflowers are in the family Ranunculaceae. Both bloom early and have pretty yellow flowers. While one appears to be modest and highly local in its spread, the other spreads so quickly across yards and into neighbors' yards and floodplains as to pose a threat to gardens and natural areas alike.

Here's winter aconite (Eranthis hyemalis) opening up a week ago in my garden, a legacy from the previous owner. Its modest spread is easily contained. I've never seen it spreading into nature preserves. Note the leaf shape, which distinguishes it from the related wildflower below.

Update: For comparison, here is one of the first blooms of lesser celandine in 2021, on March 30. Note the shape of the leaves, which are "entire" rather than lobed. Just to confuse things, lesser celandine is also called fig buttercup, and its latin name Ranunculus ficaria has apparently changed to Ficaria verna. 

People think lesser celandine is pretty, transplant it to their gardens, then begin having regrets as it spreads uncontrollably to dominate their gardens and yards. If you are one of the distraught gardeners wishing you didn't have this flower, and not wanting to impose its spread on the rest of the neighborhood, late winter is the time to deal with it. 

Other posts on this subject can be found on this website by typing "celandine" into the search box. A post called "Will the real lesser celandine please stand up--a confusion of yellows" helps with identification.

Though I'm no fan of herbicide, that tends to be the only workable option in the majority of cases. I'm no expert on herbicides, but have been told that for lawns, a broadleaf herbicide like Weed Be Gone is effective. For flower beds, a 2% formulation of glyphosate (Roundup or equivalent) works well. Monsanto doesn't hold the patent any longer on glyphosate, so it's possible to buy if from other companies on the internet. I use a wetland-safe formulation, but for most yards, away from wetlands, some spot spraying with Roundup or equivalent should be okay. The plant itself is poisonous to wildlife. 

There have been other proposed means of killing the plant: 

Mulch

If you blanket the whole infestation thoroughly with mulch, e.g. a layer of cardboard covered leaves or hay or woodchips, it might kill the lesser celandine if you mulch as soon as the plants leaf out in late winter. Chances are, you won't cover it soon enough, or you'll miss some spots, and the lesser celandine will benefit next year from the fertilizer in the mulch. 

Vinegar/salts/detergent

This concoction has shown up on the internet: 1 gal white vinegar, 2 cups Epsom salts, 1/4 cup Dawn dishwashing detergent in a hand held 2 gal pump sprayer. Spray in bright sun on a windless day.

But I couldn't find evidence that it has been carefully tested, nor that it would kill the roots. If the roots survive, the plant will be back next year. The concoction contains an acid, and the salts are made of magnesium and sulphates. These may or may not be harmful to the soil if used to excess. 

Central Park in Spring

Central Park back in April, where a glorious nature is framed by a Manhattan skyline, like a verdant postage stamp in the Forever series, 50 blocks long and 3 long blocks wide.

The land's mix of rock outcroppings and swamps, a desire to emulate parks in European countries, and a healthy dose of 20/20 foresight (short history here) all played a role in sparing this ground from economic imperatives, a place where nature can have its day, every day.

Central Park is ringed by museums of art and history, but Central Park's history is of the living sort, etched in infinite varieties of green and blue, enduring but ever changing, bottomless in its imagination, needing no roof other than the sky.

Spring migratory birds, shuttling like ambassadors between earth and sky, continent and continent, drew a crowd of admirers welcoming their return, cheering their journey, as if the birds were sailers just off the ship.

The warblers gobbled down proteins and energizing fat in the form of insects nourished by a patron oak's foliage,

while a raccoon's interest in the tree was more structural. Indifferent to our earthbound attention, it snoozed through the day in its high rise apartment (no elevator but rent controlled) in the crotch of the tree.

I could count on one hand, well, maybe two, my visits to Central Park, and yet it strikes deep chords within. Buildings are usually framed by nature, but in Central Park, its the buildings that do the framing. Get to know plants on a first name basis, and they will become like old friends you run into wherever you go. Central Park is like seeing an old friend all dressed up in a suit for the first time.

The habitat restoration being done along the trails of the Ramble are not yet Shakespearian in depth--Shakespearian here defined as the more you look, the more you see. But the restoration of expanses of native wildflowers, grasses, sedges and ferns on the forest floor is sufficient to trigger memories of the rich understory many eastern forests had just a few decades ago. Though ringed by concrete and highrise buildings, Central Park has in some ways a better chance to be natural than more rural areas thrown out of ecological balance by intense browsing pressure and unfettered invasive species.

I know of only one bluebell growing in Princeton's preserved open spaces. Central Park has many, protected from their primary threat, straying pedestrians.

A cool-season grass, presumably native, is being used on slopes for erosion control.

One reason why prospects are good for native plant restoration in Central Park is the vast pool of potential volunteers to draw on, given the auspicious ratio of NY's residents per acre of greenspace.

Not that one needs any additional evidence of the shear scale of human numbers in NY, but the Run-As-One fundraiser that day in Central Park drew 8000 participants, royally served by a row of Royal Flushes extending as far as the eye could see, that might rival some nearby buildings if stacked one upon another. Might this be an irreverent artist's vision of infinity?

How does one capture the scale of the operation, all of which must be periodically latched to stretched out trailers and hauled away for a bit of refreshing? Clearly, I digress, but then again, how many nature posts are thoughtful enough to provide a bathroom break midway through?

Segueing smoothly back into nature, here, a Fothergilla ornamenting some snazzy bins.

Park volunteers were spending a beautiful spring afternoon immersed in their own sort of marathon, pulling weeds, including the lesser celandine, that pretty but very rapidly spreading plant that had a post devoted to it earlier this spring.

The leader explained that herbicide use is not allowed in the park, so they're having to pull each lesser celandine individually. They showed me the tuberous roots. Pretty slow going, but fortunately, there isn't much of it in the park.

A few places in the park benefit from a thoughtful lack of intervention. These spent daffodils are being left unmowed so the post-bloom leaves have a chance to feed their roots for the next year.

There was some conspicuous smooching between a tree and boulder, familiar to anyone hiking the Sourlands or the Princeton Ridge. Nature has always thrived on an intimate relationship between the animate and the inanimate.

A gentle breeze propelled sailboats and memories of daysailer days.

Princeton has a couple of these Carolina bells (Halesia), one on Snowden, one on South Harrison. Strangely, almost no dogwoods were to be found in Central Park.

A frame within a frame, as nature, framed by the city, frames a sculpted shelter.

A grove of elm trees brings back memories of what American streets used to look like before Dutch elm disease swept through.

Leaving the park, we found Teddy Roosevelt in good company at the entryway to the Natural History Museum. Might he offer them horses as well? Looks like they're all trying to get back to the nature in Central Park.

Just inside the Natural History Museum, there appeared to be an allegorical confrontation between Truth and Towering Ignorance. Might Congress's high dome be accommodating something similar? Nice to see that T-rexian Truth had a nice set of choppers, though it wasn't clear who was going to win.

Losing Control of the Lawn

Most everyone has at least a little lawn, pleasant to walk upon, setting off the shrubs, or simply a default means of dealing with that rectangle of nature a homeowner inherits with the house. Collectively, lawns are a show of cultural unity in the form of a vast expression of control and uniformity, with growth kept within strict limits, each grass blade the same height. Oftentimes, the uniformity is enforced by noisy, machine-laden coiffeurs, akin to paramilitary outfits that land and deploy, then hasten away when the mission of growth-control has been achieved.

Early in spring, where chemicals aren't used, there can be small rebellions here and there in the lawn, instigated by the "early risers", e.g. assertive wild garlic, or star-of-bethlehem, forming an effect I call "lawn blotch". When the grass starts to catch up, there's a peaceful week or two of quiet conformity, the green spotted with the pleasant yellow of dandelion blossoms. And then, lulled by spring into reverie, proud of our environmental high road of chemical free lawn care, we wake up to the white, seedy roar of the dandelion, going rogue, letting its freak-flag fly, rocking the sea of green with its passion for propagation.

The photo, taken a week ago, is of my neighbor's lawn, a rental, but mine was "hearing the roar" as well. There may be approaches to organic lawn care that minimize the dandelions, but for most of us who do nothing beyond periodic mowing, the dandelions hold reign for a couple weeks each spring. The sense of losing control, though, is temporary, and though it may add to the number of dandelion seeds parachuting in to other yards, it has no ramifications for natural areas. Maybe the deer eat them, but for whatever reason, dandelions pose no threat to our stream corridors or nature preserves that I've noticed.

This contrasts with an introduced species like lesser celandine, whose rapid spread not only triggers feelings of having lost control of one's yard, but also threatens transformation of nearby preserved lands.

Letter On Lesser Celandine Strikes a Nerve

A letter I sent recently to the Town Topics newspaper in Princeton struck a nerve. It was about a pretty but very aggressively spreading nonnative flower called lesser celandine. One reader, I was told, even printed the letter out and distributed it to her neighbors, in hopes that they would take a look in their yards, and take action before the plant took over the neighborhood's flower gardens and lawns. My next post on the subject was going to be a critique of You Bet Your Garden, the widely heard radio program, whose website posting on lesser celandine is full of misinformation. It's both fascinating and alarming to see how even a supposedly authoritative source like Mike McGrath can end up spouting nonsense, which then spreads to listeners, one of whom in turn further spread McGrath's misinformation in a response to my letter published in the Town Topics this week. As with climate change, the intimidating reality of invasive species has led many people to seek refuge in denial of either the problem or the solution, or both.

In the meantime, below is the letter I wrote:

If you’ve noticed a little yellow flower starting to take over your lawn and garden, you aren’t alone. Appreciation soon turns to distress as the plant spreads to become a form of green pavement, outcompeting other plants, then leaving the ground bare when it dies back in early summer. It has lots of names—lesser celandine, fig buttercup, figroot because of its fig-shaped underground tubers, or the scientific name Ficaria verna.

Like many introduced species, it gains competitive advantage by being inedible to the local wildlife. Along with nonnative shrubs that wildlife also avoid, like honeysuckle, winged euonymus, privet and multiflora rose, lesser celandine prevents solar energy from moving up the foodchain from plants to insects to birds. This foiling of natural processes effectively shrinks the acreage of functional open space Princeton has worked so hard to preserve.

The most dramatic example of this plant’s dominance locally is in Pettoranello Gardens, from where it has spread downstream into Mountain Lakes Preserve. That situation is beyond control, but in homeowners yards, and many local parks and preserves, early detection and treatment can nip invasions in the bud. I’ve been encouraging homeowners and the town rec. department to take this work seriously, because one small infestation can quickly spread to affect downhill neighbors, parks and preserves. Effective treatments can be found online, but typically consist of using 2% glyphosate, the active ingredient in products like Roundup, the wetland-safe Rodeo, and other similar formulations.

As with the abuse of antibiotics by the meat industry, glyphosate is now vastly overused to grow bio-engineered corn and soybeans. That abuse has in part driven a demonization of herbicides in general. But just as antibiotics remain a critical medicine, various herbicides remain a critical means of dealing with invasive plants. Personally, my avoidance of herbicides is nearly total, but in the case of lesser celandine, with its tuberous roots, no other approach is practical. Only if there are just a few plants can one dig them out, bag them up and throw them in the trash, not the compost.

Adding to the distress of these radical transformations of our landscapes is a strange narrative that is showing up in places like the New York Times and the radio show You Bet Your Garden. Through a denial of both the problem and the solution, reminiscent of climate change, it claims that we should learn to love invasive species, and hate those who dare to take action against them.

This view cheats us of the deep satisfaction of identifying a problem and working together to solve it. This past weekend, as part of my work for Friends of Herrontown Woods, I was able to convince a couple neighbors of the preserve to treat their lesser celandine. By doing so, they will not only spare their own yards but also the stream just down the hill.

As a bonus, I got to meet some new neighbors. By taking our local nature’s problems seriously, we also build community.

Conquering Backyard Ivy in an Ivy League Town

After weeks of inaction, paralyzed by inertia and wondering if once again the garden would bowl me over with its growing power, I finally ventured out with gloves, dirt-friendly clothing, and some clippers to take on some of the backyard's longstanding "issues". To my surprise, there was satisfying progress to be made, that actually built on progress past.

Many gardeners have "border issues", that is, plants invading their yards from their neighbors', or vice versa. A friend recently showed me how lesser celandine was continually spreading into his yard from his uphill neighbor, and there are many stories of bamboo's indifference to society's artificial boundaries.

For years, my yard had waves of english ivy coming in from three sides, but two of my neighbors, without my saying a word, got rid of all of theirs. And where my yard abuts the park in back, I was able to get rid of the parkside ivy by taking the liberty of mowing it, after which the parks crews apparently have been weedwhipping any resprouts.

Taking advantage of the soft soil after yesterday's rain, I finally took on the legacy of ivy on my side of the fence, using physical means. The first phase was an on-hands-and-knees approach, pulling and cutting off any ivy growing on the fence.

Ivy heading up a tree got cut at the bottom. No need to pull it down. Cutting at the base is enough, though some people find it more satisfying to pull it all off.

For phase two, large pieces of cardboard were placed along the fence, overlapping, and any ivy still exposed further in was pulled out and thrown on top of the cardboard, where it will dry out. Some native vines--virginia creeper, wild grape, and poison ivy--were pulled as well, though the main goal was to eliminate english ivy. Gloves, long sleeves, and periodic washing of any potentially exposed skin with water should be enough to avoid poison ivy's effects, but we'll see.

The chickens came over to inspect my work, and seemed satisfied. Phase three would be to cover up the cardboard with chips or some other organic material that will hide the cardboard and keep it from getting blown by the wind. But the cardboard will quickly disappear behind a screen of growth in the yard, and some exposed cardboard may prove instructive to park users, who may decide to try using cardboard to deal with their own border issues.

Elsewhere in the yard was additional proof of how even intimidating weeds can be controlled by timely intervention. Only a few garlic mustards came up this year, because they've been getting pulled each spring before they go to seed.

And the big bamboo patch that once was advancing across the fence on the north side is down to a few weak sprouts easily cut. Other weeds--the Canada thistle and the dandelions--got the undercut treatment with a shovel.

There is, of course, the option of eating the young leaves of garlic mustard, and I saw a chinese woman inspecting some bamboo clones across the street, in search of bamboo shoots.

Some of the more aggressive native species got a rebalancing. A native floodplain species of goldenrod that spreads via underground rhizomes got pulled out in places. In the photo is the base of a bottlebrush buckeye--a beautiful native shrub that can start grabbing territory once established. It was a relief to discover that its expansionist ambitions are realized via above ground stolons that can be easily cut.

Mixed with the pulling and digging and rebalancing was some appreciating, of the subtle pendulant blooms of a Bladdernut, a native shrub found in only a few isolated spots in Princeton.

Native Plant Event at Whole Earth Center

On Sunday, May 1, 11-2pm, the Whole Earth Center in Princeton will have a native plant shindig. That's what Alex Levine, Whole Earth's master artisan of deli cuisine calls it. The official title is "Landscaping With Native Plants", and will feature native plants for sale and free advice from some of us landscaper, native plant seller, naturalist types. There's more info and a pretty photo of Alex's wildflower garden at this link.

Unrelated to the sale, some flowers to be enjoyed this time of year, native species occurring in gardens but not in the wilds of Princeton, is this Fothergilla I planted in the raingarden in front of the Whole Earth Center,

and, if I can get the chicken out of the way,

some celandine poppy. Unrelated to the lesser celandine that's radically spreading through gardens, parks and natural areas of Princeton, the celandine poppy is in the poppy family, makes small mounds that look good even when they aren't blooming. New ones pop up nearby, but not in a way that threatens to take over or spread unwanted into the neighbor's.

Alert: Monitoring for Lesser Celandine

Memory was finally jogged that this is the time of year to be scouting Princeton's natural areas for the dreaded Ficaria verna, a.k.a. fig buttercup, or lesser celandine. Dreaded because it has an alluring yellow flower that makes one want to leave it be when it starts showing up in the yard or local preserves, but then quietly takes over, paving whole valleys. Pettoranello Gardens is carpeted with the plant. In Durham, NC, I once tracked an infestation upstream to a homeowner's yard. He was greatly relieved to find out what plant had taken over his garden, and proceeded over the next several years to completely eliminate it. Unfortunately, by then the plant had spread far downstream and would transform a whole watershed, from one small infestation in someone's yard. He was, however, able to remove some he had put in his son's yard elsewhere in town, before it had a chance to spread downstream. This is why it's so important to get the word out about these highly deceptive species.

When I was working at Mountain Lakes, I'd walk the valley leading down from Stuart School, searching for any small patches that could be eradicated before they expanded beyond remedy. It's satisfying to be able to nip invasions in the bud. Now that my focus is Herrontown Woods, the spring ritual is playing out there. Yesterday's walk yielded no sightings until the very end, when I checked the pawpaw patch we planted New Year's weekend, and headed back through the woods towards the parking lot. There, right where the groundwater seeps out of the ground in what originally may have been a primitive septic system, was a patch of lesser celandine. Already, it has spread down the ditch about fifty feet, but is still of a size that we can eradicate it before it spreads down the valley, beyond control.

Control options can be found at this link. A comparison of lesser celandine with other yellow spring flowers, such as marsh marigold and celandine poppy, can be found here. If possible, avoid hiking through an area with lesser celandine--there's a risk of inadvertently spreading it into new areas in the treads of your shoes.

Small Aquatic Invasion in Pettoranello Gardens

Walk along the edge of Pettoranello Pond, over near Mountain Lakes in Princeton, and you'll see a band of green slowly expanding along the banks. Five years ago, when I first noticed it, my immediate thought was that a new invasive species had arrived. Even though there was only one small patch, about a yard across, it was easy to extrapolate from the present into a future where the pond water's pleasing reflections would disappear beneath a dense mat of green.

It had stems, so couldn't be duckweed, and was much too small for water lettuce. Google searches yielded nothing similar, which could at least be taken as reassuring that it isn't a widespread menace. With help from Chris Doyle, via Mike Van Clef, we determined that it was water starwort (Callitriche sp.). Seeds would need to be collected later this year to identify the species. Vernal water starwort (C. palustris) is a native species. Pond water starwort (C. stagnalis) was introduced from its native Europe and Africa back in the 19th century, and has been slowly spreading in the U.S.

Though it hasn't spread aggressively across the pond, here's an example of where it has moved beyond the edge into more open waters.

In this photo, you can see the water starwort and, popping up on dry ground, small roundish leaves of the much more aggressive lesser celandine (Ranunculus ficaria) that has become ubiquitous in Pettoranello Gardens and has spread downstream into Mountain Lakes and beyond.

Making Spring Cleaning Easy at Harrison Street Park

On the fringe of a town park, during an hour on the fringe of our day, Clifford and I prepared a public garden for the summer to come. It competes, like all to-do's on the fringes of our lives, with countless other priorties, yet it's a garden we planted together, and we're the ones who know how to take care of it. And besides, spring cleaning gives us a chance to catch up on each other's lives.

It's easy to like a garden when it's full of flowers, but now, when glimmers of green are just emerging through the spent remains of last year's glory, is when a garden's prospects for the year are determined. A "swale garden" like this one--not really a raingarden because it doesn't hold any water back--has a lot going for it. Benefitting as it does from abundant sunlight and the runoff from a parking lot, spring cleanup is easy. Knock down the old stalks, pile them up, that's it. We could have left the pile for a parks crew to haul away,

but then I noticed some mugwort starting to get established near the back fenceline, and decided to put them to use. Overlapping pieces of cardboard were placed over the mugwort, topped by the dead stalks of spent sunflowers. Less work for the parks crew, less mugwort, which has overgrown some of the other, less robust plantings in the park. Win-wins are important when time is scarce. The sticks may look a little untidy right now, but they'll quickly disappear beneath new growth, and will help cool the soil and retain moisture during the summer months.

Though the garden looks drab and static, a gardener can see the forces at work. In this springtime still-life, life is anything but still. Like schoolchildren on a slow-motion flowerbed playground, each plant species has its own personality. Some "play well with others", content to stay where they're planted. Some are bullies, grabbing space and sunlight from the less aggressive sorts. A good "playground supervisor" sees the conflicts coming, and intervenes before things get out of hand. Native sunflowers, with their aggressive underground rhizomes and height advantage, have been steadily advancing to claim the whole space. There are still some non-spreading species hanging in there. Hibiscus moscheutos, tall meadowrue and cutleaf coneflower are tall enough to compete, leaping for a piece of the sun in this botanical game of basketball, but even their years are numbered if we don't return to weed out some of the aggressors.

Years back when we planted the garden, we did a lot of things right, but made a common mistake, thinking it was okay to plant the perennial sunflowers to fill some of the copious space, because surely we'd be vigilant enough to limit their spread. Now we'd need to weed out hundreds of new sunflower shoots each year if we wanted to preserve the diversity from which comes a variety of blooms throughout summer and fall. The result is pleasing enough, though, with spectacular yellow blooms in late summer, and essentially no weeds. Any garden that's weed-free and attractive while requiring only two man hours of work per year can be considered a success.

Elsewhere in the park, in flower beds planted by contractors as part of a grand design, the weeds are getting the upper hand. What looks like undifferentiated green in this photo is really a mixed bag. There's still some diversity, but the botanical bullies are poised to take over. That big clump with pretty yellow flowers is an ominous sign. Called lesser celandine, it's a nonnative that will spread aggressively if left to grow. Now, when there's only one plant in the entire park, is the time to dig it out, put it in a plastic bag and send it to the landfill.

Garlic mustard is another aggressive spreader best pulled now, before it starts growing flowers.

Elsewhere in the flowerbed, in this sea of nonnative Canada thistle and mugwort, is one of the intended native plants--wood phlox, barely noticeable there on the right. It will soon offer a beautiful blue flower, but the best time to take action is before it starts flowering. Someone with a good eye for plants needs to swoop in and save it from the quiet sea of aggressors rising all around it.

Most native plantings are low-maintenance. Like any sort of management, if you get everything running smoothly, the manager's workload will be light. With some strategic timing and finesse, and auspicious siting of the gardens to take advantage of sun and runoff, the mutiny of Canada thistle in this photo would be caught early and kept from gaining momentum.

Who might do this work is a good question. Princeton employs only one staff person whose job it is to know one plant from another--one more staff than most towns hire. That's the arborist, whose primary focus is on trees. Another employee, in the recreaction dept, tends to the beautiful plantings around the rec offices and swimming pool, but that's above and beyond her official duties. In most parks, grass gets mowed, trees get some attention, but the rest of the plant kingdom is on its own, unless some volunteers come along with time and knowledge.

To sustain more interesting and attractive plantings, there would need to be someone who knows the plants, knows the various times during the year when strategic intervention will be most effective, and can mobilize some volunteers to do the work. If someone is, or at least feels, responsible, then parks can be a playground for plants as well as people, a place where people can get to know something of our natural heritage. A garden is a long-range commitment. If done right, it can be sustained, year after year, along the fringes of a park, with a few hours now and then, found on the fringes of our days.