Stop Stiltgrass From Taking Over Your Yard

August is the month to try to keep the uber-invasive Japanese stiltgrass from taking over your yard. People familiar with the plant may shake their heads at such a goal, but there are still many yards that are free of its plague-like qualities, whether through luck or a combination of early intervention, vigilance, and persistence.

Have you seen it? There's usually a white line running down the middle of each leaf. It looks harmless, even graceful, but stiltgrass (Microstegium vimineum for long) spreads so aggressively that it can blanket whole forests, or line roadsides for miles. Once you learn to identify it, you may start seeing it everywhere.

Michigan had until recently been spared, but here's my Ann Arbor friend Sam's backyard last year. Another friend, Victorino, who grew up in Guatamala, called it "communista." I had to laugh, if grimly, because replacing diversity and individuality with monocultural conformity and oppression is what stiltgrass does all too well.  It's a warm-season annual grass, meaning that it sprouts from seed late in the spring and matures through the summer. By late August it can grow up and over everything else, then sets zillions of seeds in September.

Because stiltgrass is an annual, the way to fight is to prevent it from successfully producing seed. 

Here's Sam's backyard after he weed-whacked the stiltgrass in July. A lot of work, but maybe effective, because I saw surprisingly little regrowth through all the resultant mulch.

Weedwhacking can also be done in mid to late August, just before the flowers form, to reduce even further the chance of resprouts that could produce seed. Do this year after year, and eventually the soil will run out of seed to sprout.

But by far the best way to keep stiltgrass from taking over is to catch it early. Even though it has blanketed many areas of Princeton, there are still substantial areas that can be saved from its smothering growth by strategic, annual action. This super plant has a big weakness: it has super weak roots, and pulls super easy.

Look closely at this photo. Do you see the stiltgrass mixed in with the other foliage? Pull those few plants, and there will be no stiltgrass to produce seed. Stiltgrass spreads into new areas of nature preserves primarily along trails, so some scouting and strategic pulling in August is an excellent way to protect large portions of preserves from incursion.

Otherwise, the trail can end up looking like in this photo.

It can even grow in a miniature form in mowed lawn.

For homeowners, where there are just too many to pull, another approach is to spot spray with a super dilute formula of systemic herbicide. You can see at the bottom of the photo how tiny the roots are compared to the plant. That's where the herbicide does its work. The Penn State Extension website offers some means of control.

Whatever combination of methods you use, it's best to start early in August. Make one pass through an area, then check back in a week or two to get any that were missed the first time through.

Though many people are intimidated by the thought of distinguishing one grass from another, it's possible to get quite good at it over time. Below are some plants that can be mistaken for stiltgrass.

Carpgrass is another nonnative annual grass, shorter, with wavy leaves, and less common than stiltgrass but similarly invasive. 

Virginia whitegrass (Leersia virginica) is a native with narrower, longer leaves. It flowers earlier and lacks the white stripe down the leaf. As with most native plants, this species "plays well with others," growing here and there without dominating.

I'm calling this one Heller's Rosettegrass, Dichanthelium oligosanthes. It's sometimes recommended for native lawns, but shows up in woods around Princeton.

Various other native Dichantheliums make life interesting. These native grasses tend to be perennials, and so better rooted and more resistant when you accidentally pull at one.

Various smartweeds can also look somewhat like stiltgrass. Smartweeds can be rambunctious, whether native or nonnative. 

Though I've despaired at the sight of stiltgrass rising in late summer like an indomitable sea in some areas, I've also been surprised and gratified to find many areas that remain free of it, and could continue to be if people act strategically year after year. 

Related posts:

Stiltgrass Reaches Michigan

Last Chance to Pull Stiltgrass -- 2023

A Video Tour of the Veblen Circle of Native Wildflowers

Here's a video tour of the circle of wildflowers we planted in honor of Oswald and Elizabeth Veblen, whose generosity and love of nature led to Princeton's first nature preserve, Herrontown Woods.

Most woods are largely silent, flower-wise, in late summer, but in the woodland opening of the Barden, where scattered trees allow sunlight to reach the ground, sun-loving native wildflowers of summer can prosper. The video was shot during a pop-up May's Cafe hosted by the Friends of Herrontown Woods.

The Barden is home to more than 150 species of native trees, shrubs, grasses, and wildflowers 

The PHS Ecolab Wetland Begins its Third Life

They say that cats have nine lives. How many lives can a wetland have? The Princeton High School Ecolab Wetland is now beginning its third. Lush and verdant in June, it was stripped bare of vegetation for the second time in its 17 year history at the beginning of July. The first time this radical change happened, in the fall of 2022, took me and environmental teaching staff completely by surprise. This time, the lines of communication were open, and the reasoning fully understood.

On June 12th, the wetland--a brick-lined detention basin squeezed between the science and performing arts wings of the school on Walnut Street--looked like this. The elderberries were abloomin' along the edges of lush sweeps of sedges, rushes, and wildflowers that thrive in full sun and ground magically kept moist by sump pump water.

There were also cattails, lots of cattails--narrowleaf and broadleaf. Cattails, with their vertical hotdog-shaped stalks raised high, are the iconic wetland plant. But when I see cattails in a wetland that I'm taking care of, my reaction is "oh, oh." You may see cattails being overwhelmed by the tall invasive reed Phragmitis in the ditches along freeways, but in a sunny wetland like the high school Ecolab, cattails themselves can play the bully, spreading aggressively with the thick rhizomes they send out in all directions.

Thus, when I stopped by the Ecolab less than a month later, on July 7, and saw all that lush, beautiful native vegetation stripped bare, I grieved the loss, but I also saw a potential silver lining.

The reason for the transformation was the need to replace two of the basin's walls. The blocks originally used to make the wall had become corroded by salt used to de-ice the adjacent walkways in winter. Replacing the blocks required complete demolition and rebuilding. The large tubes in the photo conveyed the frequent discharges of sump pump water away from the work area. 

During the repair phase, I was in ongoing communication with the contractor, Patrick, and environmental science teacher Jim Smirk. I wanted to make sure that the hydraulic conditions so favorable to diverse wetland plant growth--the combination of some higher ground with a series of three pools to transport the sump pump water slowly towards the drain--would be restored. Though I was out of town on a band tour in Michigan, Patrick was very accommodating and even sent a photo to make sure he had reformed the ground the way we wanted.

It may look like a moonscape, but already some of the old vegetation is beginning to reemerge from whatever roots are still intact. We may need to do some replanting, but after 17 years, the soil should be packed with native seed ready to sprout over the coming year.

Now is a critical time for the Ecolab's future. That first stripping of vegetation in fall 2022 had been prompted by willow trees that had grown too big for the site. As vegetation rebounded, I assiduously removed the sprouts of willows and any other trees with the potential to grow too large. This time, it's the cattails that pose a danger.

What plant species are going to feed off of all that wonderful sun and cool sump pump water from the high school's basement? If we let the cattails reestablish, the Ecolab will eventually become stuffed with cattails and little else. If instead we remove all sprouting cattails and encourage native species that are less aggressive, then it will be much easier to sustain biodiversity over time. As with the growth and development of people, intervention early on in a wetland's rebirth can determine longterm fate. 

Related posts:

A Wet Meadow is Born -- We used a similar strategy of early and ongoing intervention when a detention basin was replanted with native species in Princeton's Smoyer Park 9 years ago. That wet meadow is now thriving, with very few weeds and lots of native diversity.

The Work Behind a Natural-looking Meadow--a more recent post about the Smoyer Park wet meadow.

Summer Roadside Weeds in the Midwest

Many roadside weeds common in the midwest have yet to make it in any numbers to eastern locales like Princeton, NJ. Unless differences in climate or soil are limiting these nonnative weeds' rampancy in the east, a trip to the midwest can feel like prelude for what eastern roadsides could look like decades from now. Even if they can't compete with tough customers in NJ like the nonnative mugwort and Japanese knotweed, their behavior along midwestern roadsides shows what those first few popping up in Princeton could turn into over time. 

Here's a display of roadside weeds collected on the hood of my rental car at a rest stop. This was in Ohio, though the same roadside weeds are found in Wisconsin, Michigan, and likely other midwestern states as well. The row of blue flowers on the left are chicory. The delicate white disk of Queen Anne's lace--the wild version of the carrots we eat--is in the upper right. Yellow sweet clover--there's also a white version--is in the lower right, and the pink flower in the middle is spotted knapweed.

All of these, which seem so modest when they first show up, can ultimately form dense stands along roadsides in the midwest, as can other non-natives like the tall, dramatically shaped teasel, 

and the Canada thistle whose tops become thick with fluffy seeds this time of year (see photo). 

Less common are the tall yellow spires of wooly mullein, which in most patches appear less exclusionary in their growth habit.

One super-invasive found along roadsides in both the east and the midwest is Phragmitis--the towering "common reed" with large plumes on top that forms dense stands in ditches, displacing the native cattails. Driving on I-94 around Ann Arbor, MI, I noticed dead stands of Phragmitis--evidence they have been sprayed to save the patches of cattails the Phrag was invading. That's the first evidence I've ever seen of selective use of herbicide for restorative purposes along a freeway. 

Another nonnative I keep an eye out for, both in Princeton and the midwest, is birdsfoot trefoil. Mostly it appears as small patches of yellow in a lawn or along a roadside, but I found one instance in Ohio that shows its potential to spread and dominate, coating a large area, much like crown vetch has done where it was extensively planted for erosion control along freeways in Pennsylvania. 

What grows along roadsides can spread to grasslands being actively managed for native species. We were pulling spotted knapweed out of prairies in Ann Arbor in the 1980s. I once witnessed birdsfoot trefoil being assiduously pulled before it could spread across a prairie packed with native diversity at Kishwauketoe--a nature preserve in my home town in Wisconsin. The botanist there knew that a little can quickly turn into a lot, so better to catch those weeds early. 

The vast majority of drivers are oblivious to these roadside dramas, where a pretty flower can become too much of a good thing. For me, a drive through Ohio provides useful guidance for deciding what to weed out of a meadow in Princeton. 

Related post: Stiltgrass Reaches Michigan -- While midwestern weeds are moving east, eastern uber-invasives like lesser celandine and stiltgrass are just starting to pop up in Michigan.

Fuel Tank Raingarden, Lost to Weeds, Receives Reboot

Well, it finally happened. After five years of letting weeds get the upper hand, a maintenance crew declared defeat and tore most everything out of the raingarden next to the town fuel tank on Witherspoon Street. 

The trajectory from first year splendor to decline and fall (see links below) is a familiar one. For thirty years, in three different towns and cities, I've been watching how complex landscape plantings prosper or decline. By complex, I mean any planting containing more than three intended species.

One could talk about how maintenance is undervalued in our society. People talk about planting a tree, but few talk about the followup care--the watering and weeding that determine whether that tree survives. Good maintenance is invisible. People notice when things go wrong, not when things are kept right. This is true whether it be a well maintained raingarden or a well-run government. Both go underappreciated, at their peril. 

And we could talk about pervasive plant blindness--the scarcity of people who can distinguish one plant from another. We expect medical staff to be knowledgeable about the human body and its afflictions. A raingarden also requires expertise to keep it healthy. To weed with confidence, the landscape crew needs to be able to identify not only the intended plants but also the myriad weeds that invariably move in.

Here, in the foreground of this photo, you can see the main culprit. Though there are many other weeds, mugwort is the most aggressive non-native weed in a raingarden. Unchecked, it spreads quickly, soon leading to a sense of despair. 

Also working against success is the typical scheduling used in a maintenance department. What if the two visits per year coincide with dry conditions? Weeding is best done when the ground has been softened by rain, and before the weeds have a chance to set seed. For a raingarden to be low-maintenance, intervention needs to be strategic and well-timed. That won't happen with a rigid schedule. 

And sometimes I wonder, in this era of toxic masculinity when empathy is criticized as a weakness, whether a raingarden for some is too feminine, too complex or too hippie-like, and so ultimately yields to the masculine need to dominate with a mowing machine rather than nurture with a trowel. For whatever reason, the simplified, close-groomed look of a lawn tends to win out.

Turns out, though, that the fuel tank raingarden wasn't converted to turf out of frustration, but was instead replanted, probably at considerable cost. This suggests a commitment to maintaining the raingarden as a garden.

And yet, at the bottom of this photo, you can see the mugwort has not completely gone away. 

Like our own immune systems, constantly quelling potential riots of pathogens lurking inside our bodies, a raingarden needs someone skilled in quelling the quiet riot of weeds lurking in the soil. With vigilance and timely intervention, the job gets easier and easier and the raingarden will flourish as originally intended. A skilled caretaker would spot these weeds and pull them out before they have a chance to gain momentum.

 

Just for comparison and to show what's possible, here is a thriving raingarden in Hopewell, in front of the Peasant Grill. It remains a low-maintenance, attractive planting year after year, surely because someone with knowledge acts quickly to pull weeds before they can get established. This is the informed, timely intervention we expect for ourselves in good medical care.

But even in that well-tended planting in Hopewell, a few pesky mugwort are ready to become many if there's no skilled caretaker to spot them quickly and pull them out. Sustaining peace, beauty, and harmony requires ongoing vigilance.

Another example is the wet meadow I take care of at Smoyer Park--essentially a detention basin planted with native wildflowers and grasses. It is fed by runoff from the main parking lot.

Below are annual posts that have tracked the fate of the fuel tank raingarden, from bare ground to freshly planted splendor, followed by increasingly weedy chaos and this year's reboot. 

2020 Princeton Fuel Tank Raingarden Wannabe

2021 Princeton Finally Plants its Fuel Tank Raingarden

2022 Weeding Princeton's Fuel Tank Raingarden

2023 Fuel Tank Raingarden Threatened by Lack of Early Intervention

2024 Fuel Tank Raingarden Losing Out to Weeds

A Great Video about Pollinators on Mountain Mint

Some wildflowers are much better at attracting pollinators than others. The two champions in my book are clustered mountain mint and boneset. Back in 2008, I started documenting the many kinds of insects and other creatures drawn to the boneset growing in my backyard. Little did I know that an entomologist friend I hadn't seen since Ann Arbor college days, David Cappaert, had been inspired to do the same, 200 miles away, with the mountain mint growing in a Hartford, CT schoolyard. 

Dave had the advantage of 1) being an excellent photographer and 2) actually knowing the creatures' names. He created a remarkable video entitled "Mountain mint, one day in August," in which he documents 52 species he found on one stand of mountain mint. For its first 8 minutes, the video is a parade of colorful creatures with colorful names like bee wolf, wedge shaped beetle, stinkbug, ambush bug, jumping spider, freeloader fly, and orb weaver. 

Then, at 8:20 in the video, Dave begins describing the many interrelationships between the pollinators and their predators and parasites--a wonderfully complex food web, all "fueled by the nectar of the mountain mint." Check it out, and if you don't have any mountain mint growing in your yard, come to the Botanical Art Garden at Herrontown Woods, where in early July it's just starting to bloom. 

 

Note: We also have another kind of mountain mint growing in the Botanical Art Garden: what I've been calling narrow-leaved mountain mint (Pycnanthem tenuifolium), which is the more common species found growing naturally around Princeton, but clustered mountain mint (Pycnanthemum muticum) is the champ when it comes to pollinators. Being a mint, it also spreads quickly underground, so be careful where you plant it.

Learning and Stewardship on Princeton High School Grounds

Detention basins don't call attention to themselves, but this one found its way onto the front page of the Town Topics a few weeks ago. Located between the Performing Arts Center and the athletic fields at Princeton High School, its flora and fauna have become an object of study and stewardship for environmental science students. 

The main purpose of a detention basin is to catch runoff, in this case from tennis courts and a parking lot, and slowly release it to reduce downstream flooding and pollution. Most basins are mowed, but they can also be turned into meadows full of diverse native plants. 

Last year, the Princeton Public Schools hired the Friends of Herrontown Woods (FOHW) to oversee stewardship of native plants in two PHS basins, and to work with teachers and students. A student writeup in the Princeton Public Schools District News describes FOHW's collaboration with PHS Environmental Science students and teacher Jim Smirk to turn the basin into a native wet meadow. 

Journalist Don Gilpin followed up on that with a front page article in the Town Topics about the project. During eight sessions this spring, students combined the physical and the intellectual. Along with collecting data in the basin, the students are weeding out invasive species and planting natives. Our "Iwo Jima" photo shows the students lifting a tool shed into place that will also collect rainwater for watering plants. The shed was built from scavenged materials by FOHW volunteer Robert Chong. The rainbarrels were donated by Jenny Ludmer of Sustainable Princeton. 

The students divided the basin into a grid, with each student adopting one of the units. Each student then used a 3' square quadrat to study plant diversity within each unit. 

The sessions provided a rare opportunity for students to focus in on the individual plants that comprise our green world and begin to distinguish one plant from another. 

The cool, wet weather was perfect for planting and weeding. For some, this may have been their first encounter with a shovel, and the combination of grit and finesse required to give a plant a new home in the earth.

It was easy to identify the abundant native beardtongue blooming in the basin, harder to distinguish plants without flowers. Using the pattern of leaf veins as a clue, students learned to confidently weed out the non-native narrow-leaved plantain in their plots while leaving the beardtongue to grow. 

The outdoor learning the students are getting, ranging from applied analytical skills to plant identification, including how to safely and effectively use garden tools, will serve them well in life. As I said in the Town Topics article, many of them will have their own homes and yards someday, and if they become familiar with complex native habitats on school grounds, maybe they’ll dig up some of the lawn in those yards and plant natives.

Seven Native Shrubs Offer a Progression of White Blooms in Spring

Why do gardens and nature diversify over time?  Since most flowers last only a week or two, any gardener seeking a steady progression of blooms will naturally seek out new additions to fill the gaps. This spring, I noticed a different sort of steady progression: of blooming trees and shrubs in nature's garden at Herrontown Woods. No gardener put this steady progression together.

Flowering dogwood (Cornus florida) put on a show in late April.

Blackhaw viburnums (Viburnum prunifolium) dotted the understory with white pompoms for the first few days of May, their period of bloom shortened by the heat.

Alternate-leaved dogwood (Cornus alternifolia) followed in the second week of May, with scattered blooms in the shade,

and abundant blooms in the sun.

Arrowwood Viburnum (Viburnum dentatum) in the lowlands sustained flowers through cool days in the second half of May, 

along with maple-leaved Viburnum (Viburnum acerifolium) up on the ridge.

In the last week of May, abundant disks of elderberry (Sambucus canadensis) flowers began an extended residency.

Still to come is silky dogwood (Cornus amomum), 

which will look remarkably like its predecessors when it blooms.

There are many examples of how native plants that have co-evolved behave in an egalitarian way. Though there are exceptions, they tend to "play well with others," sharing the ground rather than bullying their way to dominance. Might this sharing have a collective advantage that benefits them all?

People trying to understand why invasive species can be detrimental will rightly point out that many invasive plants provide abundant flowers for pollinators. But if one species comes to dominate, its week or two of blooms will be preceded and followed by precious few flowers, leaving pollinators little to sustain them through the season.

An interesting experiment would be to monitor what sorts of insects pollinate the progression of blooms generated by native dogwoods and Viburnums. Have their visually similar blooms evolved to attract the same sorts of pollinators? If so, they could be thought of as a sort of tag team, collectively sustaining the needed pollinators through the season. 

Springtime Chow Down on Local Flora

Springtime, and the woods is full of fresh green foliage. With such tenderness and delectability in abundance, it's not surprising that very hungry caterpillars and other insects respond by chowing down. 

Earlier this spring, the tent caterpillars got busy in the Barden at Herrontown Woods defoliating the  black cherry trees. In the photo are one of many new "tents," and the brown, droopy remains of the previous year's.

Last year's black cherry chow down was particularly extravagant, resulting in near total defoliation that ultimately extended to the neighboring pin oak. In the process, the caterpillars built lavish highways of silk, the better to navigate over the cherry's rough "black potato chip" bark. Once the communal caterpillars had had their way with the trees, they individually wandered off to pupate, and the trees grew a second set of leaves. This relationship seems to keep the black cherry trees perpetually stunted, but still healthy enough to grace the Barden grounds. 

Another woody plant burdened by the overwrought appetites of native caterpillars is the Hearts a Bustin (Euonymus americanus). Because deer browse was preventing this native shrub from growing to maturity in the wild, we transplanted some into cages in the Barden at Herrontown Woods. For years, they thrived, but this year the webworm larvae of the American ermine moth (Yponomeuta multipunctella) showed up to chow down. As with the black cherry trees, the Hearts a'Bustin' shrubs are having to be way more generous than seems fair. 

Interestingly, the Hearts 'a Bustin' we have growing in sunnier locations are thus far sustaining less damage from the insects. Perhaps the extra sunlight strengthens their defenses.

More modest in their appetites are caterpillars found on ferns. Deer tend to avoid eating ferns, and insects may find them less edible as well.

Early in the process of creating what became the Barden, we discovered a pussy willow growing there. This spring, some of its leaves were getting "windowpaned" by larvae of the imported willow leaf beetle (Plagiodera versicolora). Like kids that won't eat the crust of bread, the larvae leave the leaf veins uneaten.

Oaks sustain a tremendous variety of insects, among them the wasp Callirhytis seminator. The wasp lays its egg on the oak, simultaneously injecting a chemical that causes the oak to create a growth called a Strawberry Oak Gall, or Wooly Sower Gall. The gall conveniently provides food for the wasp larva.

These are but a few examples of the varied ways plants support the local insect population, which in turn provides sustenance for birds.

Related post: Balance and Imbalance in Nature