Last Chance to Pull Stiltgrass

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

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

More on Stiltgrass, and a Success Story

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

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

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

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

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

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

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

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

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

Last Chance to Pull Stiltgrass

Late August and early September mark the last opportunity to pull Japanese stiltgrass before it goes to seed. An annual grass that was introduced from Asia, and which wildlife show no interest in eating, stiltgrass has taken over large swaths of the forest understory in Princeton, as well as many yards.  We called it bamboo grass when we first noticed it in the 1990s, back when I was living in the piedmont of North Carolina. It was also called packing grass, because it had in the past been used to pack porcelain coming from Asia. That's probably how it got a foothold in the U.S. 

The stiltgrass name fits when it extends it seedheads this time of year, appearing to climb up and over other vegetation, as if on stilts. Height tends to be around 2-4 feet, though it can even spread into lawns and somehow survive and reproduce as a miniature version a few inches high.

In late summer in the forest, it looks like this, ready to flower, bear abundant seed, then die. This is actually one of the smaller patches. In some invaded areas, stiltgrass extends through the forest as far as the eye can see.

In late summer, stiltgrass can form monocultures along wooded roadsides, thriving on the extra runoff from the pavement. 

Many people assume that since stiltgrass is so widespread, nothing can be done other than to wait a few hundred or thousand years for something to evolve to prey upon it and bring its numbers into balance with all the other kinds of plants currently drowning beneath this inedible green wave of supergrowth.

But there are many areas of Princeton where stiltgrass is just beginning to invade. Many yards still don't have it, or have small enough amounts to pull. Being an annual with weak roots, it is very easy to pull, and satisfying progress can be made if you have a small patch or many hands.

My strategy is to pick my spots, preferably pull it by late August, before it begins to flower, and just leave it on the ground to dry out. But even in September it can be pulled before the seeds begin to fall off. If it is already blooming and forming seeds, then either bag the pullings for the trash or, if you don't want to add to the landfill, pile it in one spot where any seedlings next year will be concentrated and easily dealt with.

We have made considerable progress in diminishing its presence at the Botanical Art Garden in Herrontown Woods, simply through persistent pulling to markedly reduce the production of seed. 

A friend at the NC Botanical Garden has found that large patches of stiltgrass can be treated effectively, before seed production, with a very dilute (0.5 %) solution of herbicide. Annual plants don't invest much in roots, and stiltgrass's weak root structure makes it more susceptible to systemic herbicide than perennial plants that may be interspersed. 

Here's what it looks like when it's going to seed. Stiltgrass seedheads look a bit like crabgrass, which is also an introduced annual that gets a late start in the spring and then seeds in late summer. What makes stiltgrass an aggressive invader of woodlands is its capacity to thrive both in sun and shade. 

On a recent walk along the Princeton ridge in Herrontown Woods, I found stiltgrass fairly early in its invasion, just beginning to form sizable patches.  Interspersed was a native grass with similar appearance--Virginia cutgrass--and it's interesting to note that the native grass, while common, does not form the large, exclusionary patches that the introduced species does. 

It's a challenge to tell the two apart. Most homeowner's yards won't have the native Virginia cutgrass, but it's interesting to compare. Here is Japanese stiltgrass, which also goes by the latin name Microstegium vimineum.

Here is Virginia cutgrass (Leersia virginica), with its longer, narrower leaves and more spread-out seedhead. 

Stiltgrass leaves often have a stripe down the middle.

Virginia cutgrass does not.

Once you start taking a closer look at the grasses along the ridge, you may notice the subtle differences between one species and another. Here's a native grass that I haven't learned the name of as yet. You can see that it has dense clusters of short leaves, in contrast to the others.

A look-alike homeowners are more likely to see is a nonnative smartweed called "lady's thumb," which has a cluster of pink flowers at the end. This photo shows lady's thumb at the bottom and stiltgrass growing up and to the left. Both are easy to pull.

Previous post on this subject: Stiltgrass's Annual Trillion Seed Initiative.

Porcelainberry: the Vine that Ate Princeton

Here it's Friday of National Invasive Species Awareness Week, and nary a post about invasive species!

First, readers should be aware that there are contrarians out there, writing books, articles and opeds, trying to deny that invasive species are a big problem. It's fascinating to analyze their mental gymnastics and deceptions, which are similar to those used to deny the reality and danger of climate change. I've picked apart their faulty logic in posts that can be found at this link.

Now, on to our porcelainberry tour of Princeton. You won't find it in shady areas, where other invasives like stiltgrass, garlic mustard and winged euonymus thrive. Rather, porcelainberry threatens to smother all of those sunny openings and edges that shade-intolerant plants depend on for survival. Porcelainberry is related to our wild grape, but much more aggressive. Your first impression will be, "What lovely multicolored berries!"

Your second impression, as it climbs up the stems of your shrubs, like this elderberry, might be, "Oh, a little rambunctious, but those berries are so pretty!"

Your third impression, as it turns your yard or park into a monocultural topiary, will be more along the lines of, "OMG! HELP!" No, this is not kudzu growing along a freeway down south. This is porcelainberry winning a modern day Battle of Princeton, with stealth and persistence far beyond anything we distracted humans might muster.

This is what a nearby patch looks like in December, just down the road from the Princeton Battlefield, along Quaker Rd between Mercer and 206. Invasive vines and shrubs can seem less overwhelming in winter, which is actually a good time to remove them. In spring and summer, though, all that growth energy can be intimidating.

And this is what porcelainberry is doing to the sunnier portions of our lovely nature trail off the DR Canal Towpath near Harrison Street. The blackbirds may say hello to the berries, but it's bye bye to the diversity of native wildflowers underneath that foliar blanket.

Turns out porcelainberry's a soccer fan. Here it is in the cheap seats at Princeton University's Roberts Stadium, at one end of the field,

and at the other.

Here it is (light blue and pink berries) in that "second impression" stage, climbing over a honeysuckle shrub (red berries) at Quarry Park. Give it a few years and it may reach the "OMG" stage.

I haven't seen much of it in eastern Princeton yet, but we'd be smart to keep an eye out and remove it before the berries mature.

Otherwise, sunny edges everywhere will look like these hapless flowering dogwoods, planted at Princeton Battlefield in 1976 for the nation's bicentenial, and now struggling to survive beneath a spreading blanket of porcelainberry.

Note: You can help liberate the dogwoods from the porcelainberry and other vines on Saturday, April 1 at 1pm. I've been collaborating with the Princeton Battlefield Society on invasive species work for the past several years, and will be leading a group to preserve the dogwoods that line the field on the north side of Mercer Street.

Another group of volunteers will be continuing the multi-year effort to reduce the bamboo clones near the Clark House, which we're actually having considerable success without herbicide. 

For purposes of identification, here are a couple closeups of porcelainberry. The berries are distinctive, with different shades of blue, red and white.

The leaves are easily confused with wild grape. This photo shows how variable is the shape.

I hope everyone's having a happy National Invasive Species Awareness Week. We'll end with a short Q and A:

• Are all nonnative plants invasive? No. Nonnative refers to origin. Invasive refers to behavior.
• Why are invasive plants invasive? Oftentimes, it's because the native insects/deer, etc don't eat them, giving them a competitive advantage. To regain the balance we lost by introducing species that evolved elsewhere, people end up having to be the herbivores, wielding saws and loppers.
• One nice thing about invasives? They get us out in the woods for workdays. 

Encountering Old (Plant) Friends at Fairchild Tropical Botanical Garden

Among the many surprising encounters we had during a visit to the Fairchild Tropical Botanical Garden--during a holiday spent in Coconut Grove, more than a year ago now--was the opportunity to sit down and have a chat with the celebrated writer and conservationist Marjory Stoneman Douglas. She's aging well. After a brief bout with death in 1998, by which time she had reached the age of 108, she still looks to be going strong 25 years later. Sitting alone on a bench, she looked like she wanted company, perhaps to tell me about her seminal book, The Everglades: River of Grass, and how she helped found the Fairchild Gardens.

Walking the paved trails that wind through 83 acres, I felt suffused with a bloom of happiness. Maybe I was empathizing with all the happy plants. In Princeton, things can be bleak in winter, but even in summer there is evidence everywhere of trees dying back due to introduced insects and diseases. This patch of Florida is by comparison exuberantly florid. 

Or maybe it was the endearing mix of impeccable and casual, which perhaps reflects the Garden's varied founders, who range from an accountant/businessman to a worldwide explorer to environmental advocates like Douglas. The grounds are at once formal and informal. Paved trails have imprints of leaves and fruits. Encountering no clear route from the parking lot to the visitors' center, we ducked through a shrub border. The lawns are manicured, and yet the plant labels are low-key, well-aged and aging well. 

Structures range from  a sophisticated greenhouse hosting tropical plants and myriad butterflies to this authentic-looking thatched roof pavilion. 

Along the winding paths, there were old friends, like this thriving ombu. Lacking true wood, it is really an overgrown forb masquerading as a tree. I first encountered it in Argentina, where stories tell of it giving shelter to gauchos out on the pampas. Its latin name, Phytolacca dioica, shows it to be in the same genus as our pokeweed. If you saw it blooming, as I did once in a park in the Recoleta neighborhood of Buenos Aires, you might think you're looking at a pokeweed 50 feet high.

How often do we get to see a baobab tree, and a massive one at that? 

Witnessing this assemblage of plants from around the world stirred all sorts of memories of past travels. This tree reminded me of a hike up into the hills outside Medellin, Columbia, in 1974, where a patchwork of hand-cultivated onion fields gave way to small hilltop forests of tree ferns and hummingbirds. 

Petrified wood triggered memories of visiting a petrified forest during a long drive through Argentine Patagonia.

And this swollen trunk brought the name "palo borracho" to mind, a name that translates to "drunken stick", in reference to the bottle-shape of the trunk. They are common along the streets of Buenos Aires. I think this one is Ceibe speciosa, the silk floss tree, closely related to the kapok tree.

The Garden's 83 acres were donated by an accountant and businessman named Robert Montgomery, who counted among his friends the globetrotting plant collector David Fairchild, who lived next door and supplied many of the plants. The garden's website describes how Fairchild "visited every continent in the world (except Antarctica) and brought back hundreds of important plants, including mangos, alfalfa, nectarines, dates, cotton, soybeans, bamboos and the flowering cherry trees that grace Washington D.C." 

The National Tropical Botanical Garden goes even farther in describing Fairchild's legacy: 

"Avocado, mango, kale, quinoa, dates, hops, pistachios, nectarines, pomegranates, myriad citrus, Egyptian cotton, soybeans, and bamboo are just a few of the thousands, if not hundreds of thousands of plants Fairchild introduced to the United States."

The desire to import plants that could prove useful for food, fiber, and other uses dates at least back to George Washington and Thomas Jefferson, but gained intensity during the golden age of travel--the late 19th century when Fairchild began his career. Plants were considered so important to the economy and security of the nation that the U.S. Botanic Garden--a particular passion of George Washington's--was placed next door to the Capitol building. That's it down in the lower left of this map. 

To 21st or even 20th century eyes, the proximity of a botanical garden to the nation's center of legislative power feels odd in the extreme. Plants are more likely now to be viewed as quaint decoration to soften the edges of our hardened world. When I visited the U.S. Botanic Garden, probably in the 1990s, the conservatory looked a bit down in the mouth, largely serving as a refuge for the homeless. More respect for George Washington's dream has been shown since then. 

Those must have been heady times, early in the 20th century, when Fairchild oversaw the import of more than 100,000 species of plants from around the world. Their utility and beauty promised to enrich our country by diversifying our farms, gardens and kitchens. Few, including Fairchild, wanted to think about the downside, as some of these imports escaped gardens and ran wild over the landscape, displacing native species. A botanical enrichment has contributed over time to an ecological degradation. 

I looked into whether David Fairchild ever came to terms with the potential for introduced species to run amok, and plan to write about it in a separate post. He was aware that some nonnatives like kudzu and lebbek were spreading aggressively, but there is no verifiable evidence as yet that he sounded a warning. 

It's heartening to see that the Fairchild Tropical Botanical Garden itself has evolved to take the threat of invasive species very seriously. According to multiple sources, it monitors closely its collection of exotic plants and takes action to prevent spread beyond the Garden's borders. I want very much to believe all this is true and will continue to be true, the better to enjoy the memory of my visit there, encountering so many old (plant) friends from my earlier travels around the world. 

Strangler Figs: Airborne Roots and Flying Buttresses

Coconut Grove, FL, where I was fortunate to spend a week with family for the holidays, is named after its palm trees, but the tree that will catch your eye more than any other is the strangler fig. 

How silly we are, these extraordinary trees seem to say, to think that trees should start life on the ground, have only one trunk, make their flowers seen and keep their roots tidily hidden. 

The strangler fig's logic is clever. How can a new tree survive in a tropical forest where existing trees cast deep shade and have a lock on soil nutrients? It starts its life as if on stilts, as an epiphyte high in the canopy, sprouting on the trunk of another tree. Oftentimes, the seeds, freshly digested by a bird, catch in the rough bark of a live oak, or a cabbage palm. Declaring itself improbably independent of nutrition from mother earth, it lives at first on air and rain, growing stems skyward and roots earthwards. When the roots reach the ground, the strangler fig's growth accelerates. The above ground portions turn into multiple trunks that envelope the host tree. That embrace can ultimately prove lethal, providing the strangler fig with a convenient supply of additional nutrients as the host tree rots away. 

 

More and more roots are sent downward, each one turning into yet another trunk when the roots reach the ground. Surely if one trunk is good, then many must be much better. The result brings to mind a cathedral replete with flying buttresses. 

The result of all this free-thinking, or if not thinking, then free-doing, is a tree you can walk through. 

This old beech tree in the Institute Woods in Princeton achieves a somewhat similar effect, though it's just one trunk that has rotted through. A closer equivalent in our forests is achieved in a more covert fashion. Trees like beech, sassafras, pawpaw, black locust, aspen, and the blackhaw Viburnum sprout new trunks as their roots spread underground, creating what appears to be a grove of trees that is in fact one individual.

Wikipedia lists 13 different species of strangler fig around the world. This one at Barnacle Historic State Park is the native Ficus aurea, whose fruits the sign says are edible. 

I'm guessing that many of the other strangler figs--those with myriad trunks like this impressive specimen at the University of Miami--are banyan trees from India.

On the left in this photo you can see some aerial roots growing towards the ground. 

Here's a closeup of a cluster of soil-seeking roots growing downward from a limb--another tree trunk in the making.

What little bamboo I saw in Coconut Grove paled in comparison to the expansionist aims of strangler figs. 

This fig appears ready to eat the pavement, 

while others drape themselves over walls, 

or probe the local infrastructure.

This strangler fig was so bold as to break into a tiger's cage.

Fortunately, there's no tiger living there now, just a couple of chickens. 

I forgot to mention the hidden flowers, which are borne inside the fruit and accessed only by a tiny wasp. Each species of fig has its own specialized species of fig wasp to fertilize it. For more reading, and some cool photos of just how tiny those wasps are, here's an interesting post. This Forest Service post describes the mutualistic relationship between the wasp and the tree, and says the U.S. has only two species of native fig. 

For anyone headed down Florida way, a good example of a banyan tree can be found at the Marjory Stoneman Douglas Minipark, named after the famed activist and author of The Everglades: River of Grass.