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. 

Princeton's Nowhere Land Might Have a Future

The municipality of Princeton's newsletter broke the news last week that the town has been awarded a $552,000 Climate Solutions grant to restore 45 acres of forest at Community Park North. Kudos to the town, and to FOPOS, which will help with the project. Now, what sort of forest, you might ask, is so degraded that it requires more than $10,000/acre to restore? I stopped by last week to have a look.

It's appropriate that the sculpture that now graces the entrance to the woods at the back of the Unitarian church parking lot appears to be in mourning. 

Many hikers who head down the trail won't notice anything amiss, but for me, Community Park North woods has the feel of a post-apocalyptic landscape. Walking its trails, you can imagine yourself to be one of the fortunate or unfortunate survivors after civilization has extinguished itself, leaving invasive species to overrun the wreckage. 

For a virtual tour, click on "READ MORE," below.

An Explosion of Spring Weeds

Ever heard of a painter whose spouse couldn't get him to paint the house? That's a bit like my backyard. While I've been doing plant work elsewhere this spring, my own backyard was quietly, stealthily taken over by an extraordinary array of spring weeds. The day of reckoning, or more likely several weeks of reckoning, has finally arrived. 

First step, photograph them and write about them, on the chance that others might too find themselves wading through a backyard full of weeds and wonder what they all are. Click on a photo to make it larger.

This one, the most ridiculously successful, is purple deadnettle. It's in the mint family, which you can tell by its square stem, but unlike many other mints, it relies on seeds to spread, rather than underground rhizomes.

Here's more purple deadnettle, with a foreground of ground ivy. Ground ivy has other names: creeping Charlie, and gill over the ground. It spreads vegetatively above ground, across lawns, into garden beds. It could be charming if it weren't so aggressive. The same can be said for mock strawberry.

Here's the ground ivy mixed in with some white clover at the bottom of the photo. The white clover hasn't been a problem, but in some situations, it too can become a sprawling mass.

Ground ivy looks like a wave here, rising out of the lawn and swamping the stonecrop Sedums. I really like the dandelions, until they go to seed, then not so much. If the soil is soft, gather all the basal leaves in your hand and give a slow, steady pull. Feed the leaves to your guinea pigs. Do people still have guinea pigs as pets?

By now, you'll recognize the ground ivy at the bottom of the photo, the purple dead nettle in the middle. Equally prevalent is hairy bittercress, which is the now brown plant in the upper left. A gardener feels a sense of defeat when, having delayed too long in pulling the hairy bittercress, its seeds come flying up at your face. It feels like mockery, the plant having successfully completed its life cycle and populated the ground with seeds for yet another year.

On the upper right in the photo are a few garlic mustards. They are edible, so I pull them, eat the seedheads, then toss the plant where it won't reroot. My yard would be full of them, too, if they were as stealthy and quick to generate seeds as the bittercress. Being larger than bittercress, garlic mustard is more satisfying to pull, and since it is slower to mature its seeds, we can go through a period of procrastination and still pull it in time. Garlic mustard is a biennial, meaning it grows some basal leaves the first year, building up energy in the root, then launches a flowering stalk the next spring. If not pulled, it will go to seed, then turn yellow and die in mid-summer, its work done. 

That's a different approach from many of these spring weeds--hairy bittercress, purple deadnettle, common chickweed, henbit, etc.--which sprout from their seeds in the fall, overwinter in the vegetative state, then get a quick start in the spring, blooming and setting seed before distracted people like me can pull them. 

At the top of this photo is hairy bittercress before it turns brown. On the left is Canada thistle, which has taken over many a garden bed in Princeton, spreading underground, popping up all over. I keep it at bay but have not been organized or persistent enough to fully get rid of it. 

At the bottom there are violet leaves. 

I'd like to say that the violets are less aggressive. They integrate into the lawn rather than taking it over, sprinkling attractive blooms hither and yon, and the leaves and flowers are good in salads, or steamed. But even they started being way too pushy in the flower beds a couple years ago, prompting a major weeding out. If salad makings weren't so easy to get in the local store, we'd be eating violet leaves, feeling just fine and with more balanced gardens to show for it.

Happy to say that I have no lesser celandine in my yard--the most problematic of the spring weeds, given its capacity to take over and then spread into the neighbor's yard and nature preserves. There was one in the yard a few years ago, but one medicinal spritz of herbicide was all it took to nip it in the bud. The leaves are reminiscent of violets, but are less curled, lighter green, and more leathery in appearance.

Mugwort, down there at the bottom, is a tough customer that has taken over many gardens, raingardens, and fields. Recurrent pulling has limited it to one place in my garden, but it spreads to form monocultures along the gas pipeline right of way along the Princeton ridge. Above and left in the photo is a kind of horsetail that has inculcated itself into one of the flower beds, probably planted decades ago by a previous owner.

I remember Veronica (speedwell) from my field botany days. It has an interesting bi-colored flower, and in our Michigan yard it had seemed harmless enough. When it showed up in our Princeton yard a few years ago, I let it grow here, but, perhaps due to a sunnier yard and abundant rains, 

it exploded this year and became, like so many problems in the world, too much of a good thing.

Chickweed hasn't been much of a problem. 

Curly dock is easy to undercut with a shovel. 

You see that little triplet of leaflets sticking out at the bottom? That's wild strawberry. I thought it would be great to have wild strawberries in the garden--native, tasty little berry. But they spread like crazy and I happened upon only one berry over the years.

Another weed that's here and there and can easily be pulled from wet ground is rough avens. To its left in the photo is a native weed called willow herb. Both of these look like they might generate attractive flowers, but don't quite generate enough show to be considered ornamental.

Wood sorrel, bottom of the photo, is a common greenhouse weed, but not much of an issue in a garden. Its leaves look somewhat like clover, but are tangy with the taste of oxalic acid.

The green leaves towards the top of the photo are jewelweed, a native annual that can be rambunctious, but which I appreciate for its tubular orange flowers that attract hummingbirds.

Most of these weeds originally hitchhiked to America from other continents. Finding early on as a gardener that most of my labors involved saving the intended plants from these overly enthusiastic weeds set the groundwork for understanding the problem of invasive species in nature preserves.

The reader may by now have concluded that my garden is largely a battleground where a distracted gardener is little match for weeds that grow 24/7. But there are areas where balance is easier to maintain, where celandine poppies, redbuds and dogwoods start a pleasing progression of flowers that continues through the spring.