August Nature Vignettes

Herein lie a series of mid-summer encounters with nature in Princeton. 

At the Barden in Herrontown Woods, where artistic photos of native plants ring the gazebo, a tiger swallowtail butterfly was caught imitating art imitating nature. Each of the 30 some wire cages harbors a different native wildflower. This one is clustered mountain mint, which is a magnet for pollinators.

Up near Veblen House, sawfly larvae chowing down on a young hazelnut's leaves adopted an S-shaped balletic pose when disturbed. Imagine everyone in a cafeteria standing up and adopting the same yoga position as you entered. With 9 pairs of prolegs, the sawfly larvae are not true caterpillars, which are defined as having only 6 pairs.

The sawflies' choreographed response is similar to that of a real caterpillar called a contracted Datana seen three years ago on lowbush blueberries also growing at Herrontown Woods. 

If you see the top of a lovely young eastern white pine suddenly turn brown, chances are that white pine weevils have paid a visit. The adults overwinter in the leaf litter, then emerge in spring. The females lay eggs in the central stem of the white pine, the larvae then eat the inner bark of the pine, cutting off the flow of nutrients to the terminal stem. 

In late July and early August, the adults emerge via small holes in the bark. The weevils are native, and the pine survives by using one of its lateral shoots to continue upward growth. Evidence of past attacks by weevils can be seen in a pine tree's crooked stem. 

Why is this gangly weed being left to grow in an otherwise groomed suburban lawn? It's a chicory that has worked its way into the heart of the homeowner by fielding an array of attractive flowers through most of the summer. The blooms of the homeowner's frontyard roses and Rose of Sharon shrubs come and go, but the chicory keeps delivering.

The flowers have a delightful shade of blue that lifts the spirit. There's a fun post about a chicory that grew gloriously out of what looked like pure concrete six years ago at a busy intersection, drawing photographers, including me. 

Liking the plant, I'd like to think it "plays well with others", that is, does not become invasive and exclusionary of other plants in the manner of mugwort or Chinese bushclover. But while traveling recently in southern Wisconsin, I did see it thickly established along a lengthy stretch of country road. But a road embankment is an altered soil that often becomes colonized by nonnatives that aren't necessarily invasive in a prairie.

I was impressed to see that this gardener on Valley Road had vanquished the Canada thistle that had pushed up through the mulch earlier in the spring. (See Weeds That Launch an Underground Insurgency.) A garden tells little of the past battles waged to create this gentle scene of coneflowers and black-eyed susans. 

A meadow needs to be weeded like any garden. Sometimes, the process of weeding, by getting us out there, leads to discoveries and a deeper appreciation of the area being weeded. Scott Sillars and I were weeding the meadow next to Veblen House recently, pulling every Chinese bushclover we could find before they could bloom and go to seed, when I discovered a plant not previously known to bloom there. 

Rose Pink (Sabatia angularis) is a biennial in the gentian family. I had been content to call it Meadow Beauty until I took a closer look and realized it has five petals instead of four. 

Another small treasure, found while cutting invasive wisteria vines in a thicket of privet shrubs near Veblen House, was an antler. It's said that shed antlers are rarely encountered because their minerals make for good gnawing by mice and other animals. This one, however, was in good shape long after being shed over the winter. 

When rains are plentiful, sensitive fern can form robust, expansionist stands that make the name seem a misnomer. But the plant lived up, or down, to its name when this summer's drought turned lush green leaves dry and brittle. 

Jewelweed is another example of a native plant that can be robust in wet weather, then get laid low by drought. A couple years ago, there were so scarce in the Barden at Herrontown Woods that we thought of helping them to spread. But the few specimens cast their spring-loaded seeds far and wide, leading to current abundance.

A lot of native wildflowers have "weed" in their common name, despite their positive attributes. Jewelweed is a good example, with its tubular orange flower that attracts hummingbirds, yet its capacity to become prolific can turn it into a weed in our perceptions.

Pokeweed is another native that can overgrow its welcome, looking sometimes elegant, sometimes gangly. More about pokeweed elsewhere on this blog, including its close relative in Argentina that looks like a tree but isn't. 

 

If you like pokeweed but find it gets way too big, you can cut it down in midsummmer, then watch it regrow in a smaller version of itself that might fit the allotted space better. This works with other tall native perennials as well.

Those who leave Princeton in August are missing out on bur season. If you find your leg covered with burs, it could be that you just walked by some stickweed. 

Here's a better photo. It's one of the plants written more about in a post called Deceptive Weeds. 

White avens is another weed that produces burs. 

If you get tired of watching paint dry, you can always drive down Route 206 towards Montgomery and watch Phragmitis reed slowly eat the road. 

You could also watch the condensate drain away from air conditioning units. Water can be pretty exciting to a gardener in the middle of a drought. Air conditioners pull moisture out of the inside air and release it outdoors. The trick is to take advantage of this water and direct it towards plants that desperately need it during hot, dry days when air conditioners are running the most.

One advantage of composting your food scraps in your yard is the surprise plants that sometimes appear among the moldering banana peels and crushed egg shells. This is a volunteer avocado growing in a Wishing the Earth Well composter.  

A friend of mine potted up one of his compost pile avocados and it's now almost too big to get out the door after a winter spent indoors.

There are a lot of native plants that show their beauty in midsummer when many people are out of town. One favorite of mine is woolgrass, which really should be called brown wool sedge, because it's a sedge, not a grass. You can call it Scirpus cyperinus if you want to sound impressive. Most sedges mature in the cool months of spring, but woodgrass develops more slowly, sending up a tall inflorescence that is attractive at all stages on its way to looking wooly.

It's been a great year for wild senna, a legume that folds up its leaves at night.

When many of the midsummer native wildflowers are looking spent, autumn Helenium unveils an array of attractive yellow flowers.

Fig Buttercup Alert--Little Flower, Big Problem

Yes, spring can be lovely, with some cheery displays of daffodils, and magnolia trees in their glory. But it's also an all too good time of year to witness with dismay and alarm the ongoing and accelerating invasion of the Princeton area by fig buttercup. Also known as lesser celandine, it's a small spring ephemeral that seduces with its pretty flower, then takes over your yard and garden.

It has already radically changed the spring landscape over in the Pettoranello Gardens and Mountain Avenue area, and I've watched it spreading from yard to yard over the past five years in my neighborhood near Hamilton Ave and Harrison Street.

These photos are from Maple Street just down from Nassau Street, where a still localized infestation is radiating out from one of the yards. A yard will have one or two plants the first year, dozens the next, quickly multiplying to hundreds and thousands. It's pretty easy to see whose yard was first by the density and extent of the invasion.

Across the street, the fig buttercup is taking over the lawn and flower beds.

The next door neighbor has an invasion in its earlier stages.

Why be concerned? There are many degrees and styles of invasiveness. I'll compare fig buttercup with other aggressive plants below, but here are the essentials: Fig buttercup is an introduced species that has escaped any limiting factors that may have been present where it evolved. It's poisonous, so nothing eats it. The seeds and the abundant underground tubers allow it to spread rapidly. It can grow in the sun or shade, garden or nature preserve.

Some gardeners may feel relief that, like other spring ephemerals, it will fade back into the ground after a couple months. But that seems small consolation as it increasingly displaces other plants that might otherwise grow.

By comparison, myrtle is a groundcover that people plant and may later regret as it takes over flower beds. But it doesn't spread down the street to ultimately pave the local watershed. It merely vexes the gardener who planted it.

By the same token, wisteria vine poses a much smaller threat than porcelainberry. Though an abandoned wisteria vine can spread over an acre or more, weakening trees and suppressing all other growth, it doesn't spread by seed, so remains localized. Porcelainberry is a vine that not only smothers all other vegetation, including trees, but also spreads to new locales by seed.

Most pesky weeds of the lawn--wild garlic, dandelion, false strawberry, ground ivy, etc--have not become problems in nature preserves because they are either edible to wildlife or intolerant of shade.

That's what makes invasives like fig buttercup and stiltgrass stand out as major threats. They spread rapidly, tolerate shade and a variety of soils, and nothing eats them. Since fig buttercup dominates in spring, and stiltgrass dominates in summer and fall, they represent a one-two punch that dominates the landscape visually, and leaves little chance for other herbaceous species to prosper. Since both are not eaten, yards and preserves become increasingly inedible for wildlife.

Fig buttercup can be confused with winter aconite, which also blooms early with a similar flower, but the leaves are much different. Though nonnative, I've never seen winter aconite spread beyond the limits of a yard.

This photo shows the native marsh marigold in the foreground, with leaves much larger than fig buttercup's, which is in the background. (For a closeup comparison of the two species, click on this link.) The marsh marigold, by the way, is very rare. I've seen it only a couple times in the wild. I planted the one in the photo, over at Pettoranello Gardens, purchased from Pinelands Nursery many years ago.

Click here for past posts about fig buttercup (lesser celandine), including a letter I wrote to the Town Topics two years ago that struck a nerve.

What to do? If there are just a few plants, you can dig them up and put them in the trash (not the compost), being careful not to leave any small underground tubers behind. But though I've had organic sympathies all my life, and don't like to use herbicides, the easiest way is to use a squirt of 2% glyphosate on the leaves (Roundup is the most common brand, but more generic forms are available), or else some herbicide more specific to broadleaf plants. We take medicines, and when used responsibly in a targeted manner, herbicide can play a similar role in nature.

Environmentalism has been too caught up in good vs. bad, when the biggest threat to nature and ultimately ourselves, whether it be carbon dioxide or a pretty little flower, is too much of a good thing.

A Sampling of May Flowers

No theme here, just flowers. Red buckeye, for instance, though this one doesn't look very red, a small tree planted occasionally along streets--this one under powerlines where it's small size should prevent it from tangling with the lines in years to come. It's native, though the only time I saw it growing in the wild was in the coastal plains of North Carolina.

Adding to the red end of the spectrum is a Rhododendron at Veblen House. We recently moved a carefully excised portion of the last known and deeply shaded native Rhododendron in Herrontown Woods--an azalea species--to the botanical garden next to the HW parking lot, to see if it might grow, thrive and bloom once again, if given some light and tlc. Native azaleas are said to have been a common sight in the past along the edge of Herrontown Road.

Princess trees are an introduced species often found along interstates. There are several growing at Herrontown Woods that we're leaving to grow for now. They bloom before leafing out.

The Japanese and Chinese wisterias also bloom before leafing out, making for a striking display if contained. If not contained, they become a menace, spreading into woodlands where they smother and weaken trees, and so dominate that nothing else can grow. Fortunately, they don't seem to spread by seed. Otherwise, Princeton would have long since been engulfed. There is a native species of wisteria that grows in the southeastern U.S.. It blooms when the leaves are already developing so is less spectacular. It is less aggressive, but even so must be planted with caution. Other native vines like virgins bower, groundnut, and Virginia creeper may not dominate in the wild, but can be surprisingly aggressive in the less competitive environment of a garden.

Fringe tree is a lovely native shrub, rarely seen in the wild. My one encounter was on some land we preserved in Durham, North Carolina. This fine specimen grows in a carefully tended garden at Franklin and Snowden in Princeton.

A less tended example is in Community Park near 206.

More common than fringe tree are native black locust and black cherry, both of which have white flowers around now. Black locust's flowers are usually high up, but this specimen along Herrontown Rd were low enough to photo. The tree has yellow, rot-resistant wood useful for fenceposts and burns clean and hot in the wood stove. Towering specimens grow near historic houses in the area, which doesn't seem a coincidence.

More whiteness comes from Deutsia, a well-contained shrub sometimes planted as a low hedge. Not native, but doesn't seem to spread into wild areas, or even in the yard.

Everyone knows flowering dogwood, made bright and beautiful by its bracts.

Sad to see many older flowering dogwoods in my neighborhood dying back and ending up as dead wood piled in the street. The loss, either to old age or to an introduced fungus that causes anthracnose, heightens the appreciation of those that survive.

Far more rare and less known than the flowering dogwood is the alternative-leaved dogwood, only two specimens of which I have encountered growing in the wilds of Princeton, at Herrontown Woods.

A World Paved With Fig Buttercup?

There are many types and degrees of invasive behavior in plants. Dandelions are weedy in lawns but cannot survive in the shade of a forest. Japanese maple and Rose of Sharon may seed prolifically in a garden, but rarely show up in the nearby nature preserve. Bamboo, kudzu and Asian wisteria become like castles in the landscape--formidable, exclusionary, and deeply entrenched but limited in extent. They form dramatic, isolated clones that fortunately leave most of the forest untouched. Stiltgrass by contrast is a frail annual easily pulled, which nonetheless can have a far greater impact, coating the ground of large swaths of forest with billions of plants. It thrives in shade but tolerates sun, spreading into garden beds and lawns.

We, with our big brains and bodies, are built to take on large, distinct foes, yet quickly grow discouraged when faced with a threat that is small but hugely numerous, whether it be an overabundance of carbon dioxide in the atmosphere, plastic in the ocean, those tiny odorous house ants in the kitchen, or a ubiquitous weed in the garden. That pile of papers on the desk falls into this category as well. If the small, numerous thing is a disease pathogen that attacks us directly, we have strong institutions that engage to defend us. But if the small, transformative force represents an indirect threat, impacting our environment--our oceans, landscape or climate--rather than us directly, we lack both sufficient institutions and the will to resist. This can be considered society's achilles heel.

As a local example, our big-little hamlet of Princeton is being gradually paved over by a little plant that is pretty, and seemingly benign, yet is also extraordinarily aggressive, poisonous to wildlife, and overwhelming in its numbers and rate of spread. By mid-summer, it will have faded back into the ground, but in spring it looks like an expanding rash coating the land. It numbers in the billions, and cannot be easily pulled. Even its common name is hard to get a good hold on, with "fig buttercup" having displaced "lesser celandine" because the plant has the buttercup flower and fig-shaped tubers. The scientific name is Ficaria verna, with verna referring to its spring growing habit.

In the photo is an advanced invasion in Pettoranello Gardens that long ago spread downstream to Mountain Lakes Preserve. The more land it covers, the less edible the landscape is for wildlife. Our investment in open space acquisition is undermined as the acreage of functional wildlife habitat continues to shrink due to displacement of natives by introduced species that wildlife won't eat.

Now the fig buttercup is spilling into the nearby neighborhood along Mountain Avenue, spreading down-slope from one yard into the next. This patch spread through the fence, and through the neighbor's yard,

then popped out under the fence on the other side, ready to head further down the street. This species behaves like plastics pollution in that it becomes widely spread for lack of any organism able to eat it. Nature's checks and balances, developed through eons of co-evolution and adaptation, are circumvented when a new species like fig buttercup is introduced from another continent.

Here it is at Elm Court, a few blocks further on, poised to spread into and eventually coat their detention basin.

There used to be some solace in thinking that fig buttercup was limited to low, wet ground, but here it has become established along a slope next to the stage at Pettoranello Gardens. Audience members will slip on it, pick up some of the underground bulbs in the treads of their shoes, and transport the plant to new locales. What will stop it from eventually paving all of Princeton?

For contrast, here is the native marsh marigold, with which the fig buttercup is often confused. It's growing on the edge of the stream in Pettoranello Gardens because I planted it there a few years back. It's bigger and more showy, but doesn't take over like the fig buttercup. This is the classic example of how many landscapes have become dominated by invasive introduced species, while the native plants become rare.

Another attractive native yellow flower in spring is celandine poppy (unrelated to "lesser celandine"). I've never seen it growing naturally in the Princeton area, but it is used in landscaping. It has a nonnative lookalike that can be weedy but not as invasive as stiltgrass or fig buttercup.

Because fig buttercup is so aggressive and so hard to remove manually, careful use of herbicide is really the only means homeowners and preserve managers have to prevent it from getting established and ultimately taking over. Early detection and rapid response are the best recipe for minimizing herbicide use. We can't wait a million years for nature to adapt and re-establish balance, as one of the more bizarre books on invasive species has claimed.

Maybe research could eventually lead to a biological control being introduced to limit the fig buttercup's aggressive spread, but that requires that institutions be in place that can afford to do the many years of research and testing required, with no guarantee of success. In the meantime, fig buttercup continues to pave Princeton, one nature preserve and yard at a time.