Time To Pull and Pile Garlic Mustard

One of the most rewarding invasive plants to weed out is garlic mustard. Unlike lesser celandine, which must be either sprayed or dug out, garlic mustard is easy to pull and pile. It's also easy to identify, with a strong garlicky smell to the leaves. Early leaves in the spring can even be tasty, which may explain why it was brought to America from Europe, as early nourishment after a long winter. 

If left unpulled, stands of garlic mustard will become denser year by year, releasing toxins into the soil that inhibit the growth of other plants (can you say "allelopathic"?). If you have a patch that feels overwhelming, here's a success story to inspire you. 

It's best of course to nip an early invasion in the bud. In any given year, you'll see two generations of garlic mustard. In the first year of growth, a biennial plant only produces leaves, gathering energy to launch a flowering stem in the second year. I just pull the second year plants, ideally when they first appear in the spring, but usually when they are in bloom and easiest to spot.

Pulling time is in April, extending into May. This first bloom, in the photo, was on April 10, but they're still blooming now. The clusters of white flowers can make weeding feel like an easter egg hunt. Last year, we had a girlscout troop pull garlic mustard that was growing along the edges of the Herrontown Woods parking lot. They got every last one!

That's the strategy, to pull every last one, before the seeds mature and scatter. If this is done year after year, the soil will run out of seeds to sprout. Each year there will be fewer and fewer plants, as the seedbank in the soil becomes exhausted. How many tasks do you know that get easier every time you do them? It's important to get every plant, every year, so the seed bank can't rebound.

Other gratifying aspects of weeding garlic mustard? Each plant is big enough that each pull provides a feeling of solid accomplishment. And the soil is often still soft in April, so the root comes out easily, especially after a heavy rain. I tell people to "grab low, and pull slow." 

What to do with them once they are pulled? Some people stuff them in plastic garbage bags and put them out with the trash, but though that gets rid of the seeds, it also makes more trash. My strategy is to make a pile. Word has it that even if you pull them in the flowering stage, they can still develop mature seeds. So don't just leave the stems scattered around the yard. If you concentrate them in one pile, it doesn't matter if any seeds mature, because the new plants will all be in one spot and easy to pull or smother. It's important to locate the pile where heavy rains won't wash the seeds away from the piles. 

We've been pulling garlic mustard and piling it like this for years around the Veblen House. This year, it took about an hour to get every last one and put them in this small pile, resting on a log, roots drying in the sun. That job's done for the year. It's a rare feeling for a gardener. I don't entirely trust it, and am going to go out again and check, just to make sure.

Protecting Areas of Princeton Not Yet Infested with Lesser Celandine

Each spring I send out an alert about the spread of a hyper-invasive plant called lesser celandine (also called fig buttercup, or Ficaria verna). Through website posts, letters to the editor, and social media like facebook and nextdoor, I've urged people to take action in their yards to prevent lesser celandine from taking over. The latest effort was a writeup in TapIntoPrinceton. 

Some weeds, like dandelions, proliferate only in lawns and gardens and pose no threat to natural areas. But lesser celandine spreads from lawn to garden to nature preserve, growing in sun or shade, lowland or upland. If left to grow, one plant will ultimately multiply to pave the landscape. Pettoranello Gardens, Marquand Park, Rogers Refuge, Mountain Lakes--these are some of the preserves with rampant infestations. As it displaces native flora, this poisonous plant makes our nature preserves less edible for wildlife.

It can be easy to despair, but the good news is that there are many yards, parks and preserves where lesser celandine is just now starting to invade, and could be easily controlled.

This is what lesser celandine looks like when it first moves in to a new area--a dense mound of leaves with a few flowers in late March and early April.

Westminster Choir College's huge lawn has only five or six of these clumps. It could easily be treated with a little spritz of weed killer (see below for some of the rationale for using herbicide). Five minutes of strategic intervention, and one's work would be done until following up with the same monitoring and treatment next year. 

Here's a sprinkling of just a few plants in Smoyer Park, all in a line, demonstrating how the weed is spread by rainwater that runs along the bottom of this detention basin. Again, this is a very quick job with minimal use of herbicide, with even less needed the following year. 

Here's a big clump next to the school garden at Community Park elementary. If they wanted to be organic about it, they could try covering it with cardboard and thick mulch for two growing seasons and hope the roots die off. Or they could dig it up very carefully and thoroughly, and throw all the plants and associated dirt in the trash.

But that doesn't deal with the clumps of lesser celandine that have spread to the CP lawn nearby. You can't dig up or mulch a lawn, and other alternatives to standard herbicides have not been proven to kill the roots, so you pretty much have to spot spray the lawn with weed killer, or else allow a poisonous plant to take over the very school grounds that a town-wide initiative is seeking to make more edible.

There's a similar dilemma at tiny Barbara Boggs Sigmund Park, where a patch of lesser celandine is spreading across the lawn for lack of strategic intervention. If not treated, that patch will begin to spread downhill, infesting neighbors' yards. 

It's common for one neighbor to let an early invasion expand, unaware of what's going on. This patch is at the back of a property that the owner seldom visits.

Here's another patch spilling under the fence and out towards the street from an infested backyard. This is the only infestation on this particular block, and could be prevented from spreading.

I told the caretaker at Nassau Arms apartment buildings about an early invasion on that property, and he promptly dug it up. Hopefully the diggings went into the trash so that they don't spread elsewhere. We'll have to wait until next year to see how effective it is, but at least there was a quick response. 

What the dramatic and largely hopeless invasions at Pettoranello Gardens and elsewhere can teach us is to treasure and protect those parts of town that can still be spared. To make such protection time- and cost-effective, we must begin by reassessing our blanket condemnation of herbicides as poisons. We don't condemn all medicines as poisons, but instead manage their varied toxicities by applying them selectively and minimizing dose. The same applies to managing a park or one's yard. 

The pandemic dramatically taught us that what each of us does, intentionally or not, affects others. The lesser celandine in one yard or park can easily spread to neighboring areas. This is both humbling and empowering. It tells us that what we do matters beyond the borders of our lives and our yards. Strategic action by the town,  businesses, and residents can stop these infestations while they're still easy to stop. 

Reading the Landscape Along the Towpath -- Early Spring

One place that gets a lot more interesting if you know plants is the towpath along the Delaware and Raritan Canal. For those into reading the landscape, the section just upstream of Harrison Street in Princeton makes for a good read, packed with history, beauty, poignancy, and the drama of invasion. 

First, there's the water, here with branches of elderberry reaching out over the canal in the foreground. Elderberry characteristically sprouts leaves earlier than other native shrubs. Water teaches the richness that reflection can bring to life. 

Along this stretch of towpath, the strip of land between the canal and Carnegie Lake widens, making enough room for a nature trail loop that for nearly 20 years has given hikers and joggers relief from the linearity of the towpath. Part of my life has been dedicated to making interesting destinations along very long trails, whether in Durham, NC or in Princeton. With a hardwired devotion to things, I've been an advocate for this little nature trail, and the unique, savanna-like habitat it winds through, since it was created nearly 20 years ago. Periodically stopping by to check that the trail hasn't been blocked by fallen trees, reading the landscape as I go, I always come away with a mix of joy, gratitude, and grief. 

Some flowers encountered during this walk are native, like this red maple reaching out over the trail.

Then there are some non-native species that fortunately aren't invasive, and speak to past intention. These photos were taken a week ago, when the ornamental cherries were just starting to pop. 

These really old ornamental cherry trees are reminiscent of those planted along the Potomac River in Washington, D.C. long ago. The cherry trees and the yellow spray of forsythia off in the distance show that this seemingly wild stretch of the towpath is actually populated with botanical remnants of another era, back when the university installed these plantings as an ornamental entryway to the campus. 

Adding to the evidence of past caretaking is a derelict row of winter honeysuckle (Lonicera fragrantissima), with very small, very early, and very fragrant flowers. Though it's included on invasive species lists, I've never seen it spread. 

If you're an environmental advocate at a local level, a walk can become a review of past successes and failures. For years, the DR Canal State Park, of which this ribbon of land is a part, would keep this nature loop mowed, but then their maintenance budgets started getting cut. Around the time one of their longtime mowing crew members died, they decided to turn mowing over to the landowners--Princeton University. That handoff happened at an administrative level, but not on the ground. After trying in vain to get the university to take care of the trail loop, I finally contacted Shana Weber at the PU sustainability office. Thankfully, she was able to reach the right people, and the trail is now being kept open. 

But one bit of mowing that the state parks people used to do has yet to be picked up by the university. And here's where the landscape's story shifts from joy and gratitude to grief. The nature trail loop winds through what for many years has been a savanna-like landscape of scattered trees and fields. Scattered trees allow enough sunlight to reach the ground to power a rich understory of wildflowers and shrubs. But due to a lack of annual mowing, that special landscape of forest openings, seldom found elsewhere, is being lost. Here is a forest opening that has become a layer cake of invasive plants, with multiflora rose blanketed by a web of super-aggressive porcelainberry vine. 

Other invasive vines also run rampant, like this Japanese honeysuckle smothering a branch.

Why is no one cutting the oriental bittersweet at the base of this tree, the wild gardener in me asks.

Many of the trees were planted, then ultimately abandoned, leaving a kind of derelict arboretum.

Some trees have succumbed altogether to introduced insects or disease, most commonly Emerald ash borer or bacterial leaf scorch. 

On the ground, the uber-invasive lesser celandine is laying a claim that will surely expand. 

Without annual mowing to sustain the forest openings, a tortured form of succession is underway, with sweetgum saplings being mobbed by the invasive vines. Annual mowing would sustain the special forest openings and reduce the smothering invasives.

A couple places where the native species are doing well are, not surprisingly, in standing water. Here's a rosette of a very healthy rose mallow hibiscus (Hibiscus moscheutos), its feet very much in water.

Here's a shrub that also flourishes in standing water, buttonbush (Cephalanthus occidentalis). 

There are lots of native plants that can thrive in floodplain habitats along the canal. If the university ever gets interested in habitat restoration, this would be a great place to start. It would be a high-visibility demonstration, to be witnessed by all the hikers, bicyclists, and joggers passing by, who currently see not the history and the ecological drama but just another stretch of green.

Spring Photos From Herrontown Woods

While I've been documenting the imperialist tendencies of nonnative lesser celandine in Princeton, ever vigilant, some friends have thankfully been sending photos of local nature that speak to beauty, stability and enduring diversity. 

Joanna Poniz sent some lovely photos of a wood frog in one of the vernal pools at Herrontown Woods, 

and skunk cabbage growing up against a boulder.

Oftentimes patches of trout lilies have lots of leaves and no flowers, so it's special to find one.

Here's a nice patch of spring beauties.

Local botanist Betty Horn also periodically sends photos, documenting the ongoing survival of hepaticas at Herrontown Woods, and an especially large patch of spring beauties on the trail to Council Rock in Woodfield Reservation. 

Joanna captured a threefer here, with trout lily, spring beauty, and bloodroot growing together. This is a good example of how native species have a tendency to intermingle, creating concentrated diversity.

Inge Regan captured this twofer, which looks like a onefer until you take a closer look and realize that the smaller flower isn't another bloodroot but instead a rue anemone.

Joanie Marr sent these photos of the many different kinds of daffodils growing around Veblen House and Cottage at Herrontown Woods. 

Someday I'll learn the names of all of these varieties. 

I was happy for Joanies' photo of the black vulture that hangs out at the Veblen Cottage this time of year. We got beyond viewing it as a bad omen, and now take pleasure in its annual return. Seeing it perched alone on a branch, I worry that something may have happened to its mate. They mate for life, and this pair has for many years raised young in the corncrib next to the red barn. Maybe it's just standing guard while its mate tends the nest. I'd check the corncrib to verify, but don't want to disturb.

No matter how endearing, it's still hard to end a blog post with a vulture, so back to Joanna's frog. 

Wisteria's Tamed and Wild Twinings

The front porch of Morven has an educational feature for gardeners.

Go to the right side of the porch and witness Chinese wisteria twining up and to the right. 

Go to the left end of the porch and witness Japanese wisteria twining up and to the left. 

This contrast in twining direction appears to be a thing. There's agreement that the two species twine in opposite directions, but disagreement on how to describe it. The Japanese wisteria's winding up and to the left is described as either clockwise or counter-clockwise, depending on the website. The two websites I happened upon agree, however, that the direction of twining is not determined by whether the plant evolved in the northern or southern hemisphere. This is disappointing, as I had hoped for a pattern, which would be all the more satisfying if it happened to match the direction of swirl when water goes down a drain. Alas, some other force must be at work.

What Morven's porch won't show you is just how aggressive wisteria's twinings can become after a garden is abandoned. To comprehend the scale of expansion, you would need to travel to Herrontown Woods, where the extent of a wisteria clone (Japanese by the look of its twining) is still apparent in the woods. There are two clones, both covering more than an acre each. At their exuberant zenith, they had grown up and over trees and rendered the ground a monoculture of their foliage. One clone, up at Veblen House, is now mostly vanquished, in large part due to the extraordinary persistence in years past by Kurt and Sally Tazelaar. The success of that work depends, however, on ongoing vigilance to cut any sprouts still rising from the remnants of its sprawling root system. 

We are still very much in battle with the other clone, however, across the stream from the Barden. Each year for about four years now, the town has paid contractors to spend a couple days each summer applying systemic herbicide to this or that side of the monster. The herbicide is absorbed and translocated down, to weaken the wisteria's massive network of roots and runners. I think of it as comparable to the medicines we use to maintain our own health, well targeted and no more than necessary. 

Then, this past fall, a volunteer named Bill Jemas (posing in the photo with a wisteria vine) contacted the Friends of Herrontown Woods, looking for a good project to give him the equivalent of a workout in the gym. He came several times a week for much of the fall, working largely on his own, checking in with me periodically with a question or two. Cut, cut, snip, snip--he took on the still very intimidating tangle with hand tools and perseverance, making the hillside navigable once again, dotted with piles he made of the cuttings. He then announced his family was headed to Florida for the winter. Reportedly returning this spring, his contribution to the battle has already given us hope that the wisteria monster will not eat the Barden, towards which it was headed, and can be subdued like the one at Veblen House, so that we need only snuff out a few stray sprouts each year. 

A couple related posts:

Another Perilous Embrace--Wisteria and Horse Chestnut : About the horse chestnuts near Morven, and the horse chestnut that was getting overrun by wisteria in front of the 1755 house at 145 Ewing Street. Why does one often find a horse chestnut growing near a historic house? Because they bloom around Memorial Day?

Trees and Thunderbolts : The puzzling story on the Morven grounds of how a thunderbolt killed not the tree it hit, but the tree next to it.

The Specialist Bee That Pollinates Spring Beauties

Spring beauties are beginning to flower at Herrontown Woods. There's a bee that specializes in pollinating the flower. It's a mining bee, in the genus Andrena. The common name stems from its capacity to dig an underground home. The bee only spends a few weeks each year above ground, collecting pollen that it then forms into balls to nourish its progeny. Spring beauty is our most common spring ephemeral. Next time you're out, see if you can spot a bee. Chances are improved during the warmest part of the day. 

The video was taken by Inge Regan, board member with Friends of Herrontown Woods and leader of the Invasive Species of the Month Club, which meets from 10:30 to 1pm on Sunday mornings.

A previous post of mine describes a curious behavior of the bee when disturbed, and includes info about a honey bee swarm seen in Herrontown Woods this time of year in 2020.

A "Bug of the Week" website offers a more detailed description of the mining bee's lifestyle. 

Coyote Spotted at Princeton Battlefield

 A coyote was spotted at Princeton Battlefield this past Friday, March 24. 

Thanks to David Padulo for sending around this photo of the beautiful animal. 

At the time, David (hopefully not the coyote), was on his way to Port Mercer "to check off a Mercer County Life bird (Tundra Swan)," and so happened to have his camera. Port Mercer, for those like me who would assume there aren't any ports near Princeton, turns out to be just a couple miles upstream: the historic settlement where Quaker Road crosses the canal. According to David, the tundra swan was off track, a half hour away from where they are more typically seen, at Assunpink in Monmouth.

As an avid birder, David has taken an interest in Princeton's birding mecca, Rogers Refuge, and now leads the Friends of Rogers Refuge. David, shown here carrying a wood duck nest to a more auspicious location, represents a new generation of stewardship at the Refuge, taking over from Lee and Melinda Varian, who have done so much to keep trails open and control invasive species. 

Turning 83 has not deterred Lee from wielding a chainsaw to maintain the refuge. After meeting with David to discuss how the refuge's marsh might hold more water (a lot of water drains out of the refuge where this photo was taken), Lee and I spent a highly productive hour cutting a clone of wisteria vines that has been growing up and over some trees. If left to grow and expand, the wisteria would eventually swallow the forest surrounding this remarkable marsh. The nonnative wisteria can expand without restraint because there isn't the equivalent of a coyote to keep it within bounds. 

Princeton Environmental Film Festival

The Princeton Environmental Film Festival begins this Friday, March 24. Check out the schedule.

One movie with local connections is Dark Sacred Sky, featuring Princeton University astrophysicist Gaspar Bakos, an advocate for reducing the waste light that has deprived us of the beauty and fascination of the night sky. Gaspar has been helping us prepare a telescope for use at Herrontown Woods.

According to the website, 

"Dark Sacred Night" is a special storytelling project of the Princeton University Office of Sustainability. The screening will be followed by a Q&A with filmmaker Jared Flescher and Bakos."

May's Cafe and a Nature Hike--This Sunday in Herrontown Woods

This Sunday, March 5, I'll lead a late-winter nature and history walk at Herrontown Woods.  

Meet at the main parking lot off Snowden Lane at 11am. 

Come early to get coffee, homemade treats, and conversation at our pop-up May's Cafe at the Barden from 9-11. 

There are a few signs of spring. The snowdrops are in full bloom at Veblen House. At least one of the black vultures has returned to the corncrib near the Veblen Cottage, where it and its mate have raised their young in past years. And we have an interesting sustainability project going on: milling fallen trees into lumber to use to build a boardwalk.

Considering the Chinese Praying Mantis an Invasive Species

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

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

Past posts on praying mantises.

A New Environmental Resource Inventory for Princeton Takes Shape

There's a nice writeup on Princeton's Open Space Manager, Cindy Taylor, in TapInto Princeton. She'll be leading a presentation on Wednesday, Feb. 22, about the new edition of the Environmental Resource Inventory (ERI) that she's been working to prepare for Princeton. Among the many others contributing to the update are councilwoman Eve Niedergang and members of the Princeton Environmental Commission (PEC). The PEC will host the presentation, which should get going soon after 7pm. The public is encouraged to tune in and participate.

If you are wondering what an Environmental Resource Inventory is, you can take a look at the current ERI, which I played a considerable role in creating. Starting in 2007, as a member of the PEC, I worked closely with a consultant, Chris Linn, on that previous update of the ERI, the first update since 1978. 

It seemed appropriate that a resource inventory would include plant inventories--long lists of which plants are found where in town. And so the next year, in my role as resource manager for the Friends of Princeton Open Space, I led many walks in various preserves to inventory the plant life. With help from a Princeton University summer intern, Sarah Chambliss, we compiled 22 plant inventories. 

I added many photos, and a section on invasive species, including mention of the emerald ash borer. Though the ash borer had yet to reach NJ in 2010, it has by now already killed most ash trees in our area, just 13 years later. 

To document some environmental history, I'll mention the following. The PEC, chaired by Wendy Kaczerski at the time, paid for the 2010 ERI using borough and township funds and a matching grant from The Association of NJ Environmental Commissions (ANJEC). The study was carried out by the Delaware Valley Regional Planning Commission (DVRPC), with input from the PEC and borough/township staff. 

Chris Linn of the DVRPC did most of the work to compile and write up the ERI. That document has served the town since it was published in January, 2010. Some of the acknowledgements are below. Looking at the names now--among them Rosemary Blair, Grace Sinden, Casey Lambert, Vicki Bergman, Greg O'Neil, Charles Rojer, Wanda Gunning, Gail Ullman, Ted Thomas--brings back good memories and is a reminder of how deep are the roots of environmental advocacy in Princeton. 

Liquid Winters and Time-Bending Blooms

Long time local botanist Betty Horn sent me an email some days back--February 10, to be exact--reporting that she had just found a hepatica blooming in Herrontown Woods. Hepaticas in early February? This was news. 

Without asking, I knew nearly exactly where she had found it. If you're a field botanist, you maintain a mental map of where you've found certain special plants growing, and in Princeton, my mental map has exactly one location for hepaticas, along the ridge in Herrontown Woods. Sure enough, she had found it there, given a head start by the warmth of a nearby boulder and the snowless winter. 

Hearing the news, another botanist friend, Fairfax Hutter, checked out some hepaticas she knows of in Hopewell. No flowers, nor any buds, she reported. Betty looked back at her records and told me that "the usual time for hepaticas to bloom is early to mid March, and sometimes as late as the first week in April." 

Another early flower is snowdrops--a nonnative spring bulb that decorates the grounds around Veblen House. The first bloom I noticed this year, for the record, was on Feb. 6.

Before moving to Princeton in 2003, I lived in Durham, NC for 8 years. Winters there were much like the one we've had here in New Jersey this year. The default was no snow, and if a snowstorm did come, it became a spontaneous holiday, with schools shut down for several days. It could be said that New Jersey is the new North Carolina, with Georgia in hot pursuit, so to speak. 

The shift towards a liquid winter has made for dramatic changes in our "fillable-spillable" minipond in the backyard. It's a 35 gallon tub that captures runoff from the roof, originally conceived as a pond that could be easily emptied when our pet ducks had made it muddy. 

Like an artist who has lost inspiration, it hasn't produced very interesting ice patterns the past few winters, nothing like that stretch from 2018-19, when intermittent freezes and thaws caused it to behave like a canvas for the profound artistry of nature. Each freeze would bring new and endlessly varied patterns in the ice. 

How Fallen Leaves Can Reduce Flooding

A kindred spirit in Durham, NC, naturalist Riverdave Owen, took the time last fall to count the fallen leaves freshly fallen on one square yard of his land near the Eno River. 

Posting this photo on facebook, he said the count totaled 1600 leaves. "After extrapolating that count, I estimate this year's autumn leaf drop for this entire half acre property to be approximately THREE MILLION LEAVES! Instead of raking, blowing and hauling them away, they are left as food for a myriad of tiny intermediaries who then return the foliage's organic nutrients back to the trees from whence they came .."

As Riverdave points out, the habitat created by leaves certainly is important. Just think of the spectacular increase in surface area they provide when they fall on the ground. Each leaf has surface area on front and back, and as they accumulate they create myriad tiny spaces inbetween. 

An additional benefit of leaves that tends to go unmentioned and unexplored is the impact of leaves on stormwater runoff. If I had the patience to collect data, I would take that square yard of leaves, weigh it when the leaves are dry, then soak the leaves and weigh them when wet. The difference in weight would be the amount of rainwater sequestered by the leaves themselves during a storm. Multiply that by all the square yards covered by leaves in a community, and you'd find out how much water is absorbed by leaves rather than contributing to downstream flooding. 

But leaves do more than absorb rainwater. They also help make the ground beneath them more absorbent. Exposed soil can harden and dry out, making it behave more like impervious concrete when the rains come. If instead the ground is covered by leaves, the leaves' slow decomposition softens the soil with organic matter and promotes soil life whose activity in turn opens up and maintains channels for water to seep into.