Wildflowers of August

Sound the trumpets! The main course of summer's feast of flowers is underway. Time to gather them into one big blogpost bouquet.  This collection is gathered from my backyard and from the botanical garden at Herrontown Woods.

Rose mallow hibiscus (Hibiscus moscheutos)

Wild senna (Senna hebecarpa)

Cup Plant (Silphium perfoliatum)

Joe Pye Weed (Eupatorium sp) in the background, boneset (Eupatorium perfoliatum) in the foreground.

Cutleaf coneflower (Ratibida laciniata)

Jewelweed (Impatiens capensis)

Ironweed (Vernonia novaboracensis)

Purple coneflower (Echinacea purpurea), with some bottlebrush grass on the left.

Woolgrass (Scirpus cyperinus) -- a sedge that grows taller and matures later than most native sedges

 Groundnut (Apios americana)

Cardboard Quells the Chaos--Renovating a Garden Bed

When plants aren't "playing well with others," sometimes one has to lay down the law. That's what happened in an area of the garden that got away from us. While we were off living our lives, Lizard's Tail, sunflower, and a common goldenrod were quietly sending their rhizomes out in all directions. Ground ivy and mock strawberry were overwhelmingly undertaking relentless stoloniferous expansions. And the once endearing, highly edible blue violets were pushing their way into every nook and cranny.

Some nature writers congratulate themselves on their tolerance for all living things, but that tolerant pose somehow doesn't extend to species that threaten people, e.g. COVID-19. A lot of the love gardeners feel for the plant world is expressed, ironically, by killing some plants that are threatening others. I may love red oaks, and can see that even poison ivy has an ecological role, but that doesn't mean I'm going to let a thousand seedlings take over a garden bed.

In extreme cases, where the desired and undesired become hopelessly entwined, or a garden path disappears in a sea of "way-too-much-of-a-good-thing" overgrowth, it's time to bring in the cardboard.

Yes, cardboard. Given all the negative forces in the world, cardboard stands out as a beneficent presence, rivaling that of chickens, or perhaps peanut butter, outstanding in its inborn capacity to do good with very little downside. Occupying a niche somewhere between wood and paper, cardboard can take myriad shapes to serve myriad purposes, whether keeping stuff together in a basement or rising into high art at a museum or on a stage.

In a garden, cardboard serves in a sprawled state, depriving weeds of sunlight, and creating a barrier that's strong and lasting enough that weeds can't push through. Some people use landscape fabric, but over time soil begins accumulating over the fabric, weeds grow on top, and the buried fabric then becomes a nuisance that needs to be pulled out and thrown away. Cardboard serves as a barrier for a season or two as it slowly decomposes, leaving no trace.

Here's the legacy of neglect, with path stones retrieved from the chaos,

and a tangle of way too aggressive sunflowers and violets. All are beautiful in their way, but hard to keep in balance with everything else.

Before laying down the cardboard, a few beebalms and lizards tail were retrieved from the mess with the intention of planting them elsewhere.

A variety of sizes of cardboard are useful. I put a few desired plants in--the sort that don't spread but instead grow in bunches--like ironweed, boneset, hibiscus, culver's root, tall meadow rue, cutleaf coneflower--then surround them with overlapping pieces of cardboard. More plants can be put in along the seams or by punching a hole in the cardboard. The walkway stones were put back in place, and other stones used to keep the cardboard in place until we can cover it with mulch.

Here, for instance, we're using cardboard as a base for a walkway around the "Veblen Circle" of native plants at the botanical garden next to the Herrontown Woods parking lot. A stone border is laid along one edge of the cardboard, and chips are placed on top, completely disguising the cardboard. The result is a weed-free path for a year or two. That's a whole lot easier than pulling each individual weed.

A Pettable Blue-Winged Wasp's Mating Frenzy on Princeton Campus

This post gives a demonstration of wasp petting, and describes a funny thing that happened while helping our younger daughter move into her college dorm.

There's a wasp that's both pretty and pretty harmless. It's named after its wings, which reflect blue in the sunlight, and is easily identified by the rusty orange abdomen with two yellow spots. Scolia dubia, as it's called in latin, is a frequent visitor to the boneset in our backyard garden, more methodical in its nectar drinking than many other wasps.

It's understandable that people are afraid of wasps, given the stings most of us have endured after accidentally stepping on a yellow jacket's nest out in the field. But not all wasps are social like a yellow jacket, or even have nests. A female blue-winged wasp (males cannot sting) has no nest to defend, but rather digs down to lay its egg on an underground grub, then leaves the egg to hatch, consume the conveniently paralyzed grub (usually a larva of the June bug or the Japanese beetle), and emerge on its own as an adult.

Here's an example of how docile these creatures are as they peacefully sip nectar.



This year's visits seemed less frequent than in previous years, leading me to wonder how the species is faring, given all the talk of pollinators being in trouble.

That question was answered in the most unexpected way. Helping our younger daughter move into a dorm for her first year at Princeton University, I noticed one of these blue-winged wasps on a flower near the entryway. Then, on the third or fourth trip in with stuff, I happened to look over at the lawn in the courtyard, and noticed that hundreds of the wasps--let's call it an even thousand--were roaming in zig-zaggy patterns just above the grass. It wasn't at all obvious what they were doing. They looked lost, each flying around and back and forth in its own orbit. Perhaps the grounds crew had blocked their nest, leaving them to search in vain for the entrance. One passerby joked that the wasps were a metaphor for incoming freshmen. Another suggested that the University should take action on what seemed like a threat to the students.

My sense was that any danger was more perceived than real. Having spent many hours this summer photographing the various pollinators visiting the backyard boneset, seeing how harmless are the various bees and wasps when preoccupied with other matters, I waded out into the fray to have a closer look. Were they in fact lost? Or hunting? Or mating? There was no sign of prey, and if they were mating, then why was there so little interaction?

The first clue came only after watching them for awhile. Every now and then, some 20 or 30 of the wasps would suddenly converge on one location in what appeared to be a mad scramble in the grass. It's not easy to photograph wasps zipping around your ankles, but I did manage this photo.

And also this video of one of the sudden convergences. If they were fighting, it appeared brief. If they were mating, it looked pretty clumsy.



Some internet research made it clear that the goal of this mass, planar mingling of wasps was to mate. Some websites state that the males and females do a figure eight-shaped mating dance. Others suggest that those cruising the grass are males waiting for a newly mature female to emerge from the ground. They then converge on the female and compete for a chance to mate. If one's heart can go out to a wasp, my heart went out to the hapless female who, having just emerged as an adult from its underground birthplace, must immediately deal with a frenzied crowd of males seeking to pass along their genes to the next generation. If that is true, though, the sheer numbers and intensity of the gathering suggest that a whole lot of hatching was going on that day, and might the males have also just emerged from the ground? The explanations weren't quite making sense.

I did manage to get up close and personal with one of the convergences, close enough for a voyeuristic view of a male and female taking a tumble amidst the grass blades, clearly mating, with another male up next to them, bending its abdomen and probing in vain. What was surprising was how quickly most males gave up on the project, quickly returning to their holding patterns above the grass.

Here's the online description that best fits what I saw, in a 2016 paper entitled "The Scramble Competition Mating System of Scolia dubia" 

Males of the wasp Scolia dubia search for emerging females by flying low over the ground in areas, such as lawns, that contain the immature scarab beetles upon which the grubs feed. When an adult female emerges and is discovered by a searching male, other males often join the discoverer, forming a frenzied ball of males around the female. When captured along with these males by an observer, a freshly emerged female continues to attract males even after she has mated, presumably because her scent continues to be detected by other males. Some males of S. dubia also search for mates in shrubs and trees encircling a lawn as shown by the sexual response of these males to a frozen but thawed female placed in a shrub or tree known to be visited by flying males. Male flight activity peaks around midday but then diminishes as the afternoon proceeds. 

It was in fact late morning, sunny, warm, and some of the wasps were flying about the branches of the evergreen tree in the middle of the field. But there are many lingering questions. Do these gatherings happen only once per year, or multiple times in the summer? Was this lawn special in some way, or does this happen all over town? And how did these rituals play out before lawn mowers were invented?

One thing is clear. These docile wasps do us a favor by preying on a notorious garden pest--the Japanese beetle. Maybe some September, walking home from the Dinky station, you'll cut through campus and some late-flowering thoroughworts will catch your eye. There, in the clouds of white flowers, blue-winged wasps will be busy living their quiet lives, minding their own business while doing good deeds, their solitary pursuit of nectar giving no clue as to the elaborate choreography that brings them into being.

Attracting Pollinators With Boneset and Thoroughwort

Many people sing the praises of mountain mint and goldenrod for attracting pollinators, but my two favorites are a duo that produce large disks of small white flowers for a long stretch in mid to late summer.

This has been a banner year for boneset and its more numerous but lesser known sidekick, late-flowering thoroughwort.

With a name that spreads like the pagoda-shaped stems that carry its flowers, late-flowering thoroughwort adorns the sides of roads and railroads this time of year. I've seen it cover a whole abandoned field in Montgomery,

and there's a lone specimen blooming at the end of the track at the Dinky station.

It could be called a successful weed, and sometimes it can look a little ragged, perhaps influenced by how much rain comes. But this year it was the most elegant plant in the garden, its loose clusters of flowers like delicate hands reaching out to pollinators.

Late-flowering thoroughwort (left in this photo at the Westminster parking lot raingardens I care for) blooms just as boneset (right) is fading, which this year made for a seamless handoff between the two. Though boneset is comparatively rare in the landscape, it will make seedlings to increase its numbers when planted in a garden.

The two species can easily be told apart by checking the leaves. Boneset has pairs of leaves that are "perfoliate", which is to say they fuse to wrap around the stem. Thus the latin name Eupatorium perfoliatum.

By contrast, the leaves of late-flowering thoroughwort have petioles that extend the leaf away from the stem. The "serotinum" in its latin name, Eupatorium serotinum, means late summer. We could call it the serotinal thoroughwort, but we don't. In the common name, the word "wort" means plant, and if there's anything thorough about a thoroughwort, it's the copious blooms.

Both these wildflower species rise each year to the perfect height for viewing all the varied insect life they attract. Spend some time in that honey-scented space around the flowers and you'll discover an ecosystem in miniature, the flowers being a stage where the protagonists not only feed on nectar, but also look for mates, and sometimes put their lives on the line.

You might think it dangerous to be in proximity to the many kinds of bees and wasps that frequent this floral saloon, but I have never been stung in all my hours immersed in quiet observation.

I've even taken to petting the more docile creatures, like this "solitary" blue-winged wasp. Knowledge can cut through fear. It helps that the more aggressive insects, such as "social" wasps like yellow jackets, spend their summers elsewhere.

If anything, the pollinators are at much greater risk than I, with an occasional preying mantis showing up to snare a fly,

or a brilliantly disguised ambush bug lying in wait for a bumble bee.

Here's the ambush bug that was hiding in that previous photo.

Each plant has a time-release approach to flowering, with some clusters of flowers opening just as others are fading. Week after week in the summer, working in tandem, boneset and late-flowering thoroughwort continue to play host to a shifting cast of insect characters--each with its own traits, backstory and motivations--all the while adding ornament to the garden.

Visits By Butterflies

One perk for us stay-in-Princeton types in the summer is the fabulous display of native flowers--the tall, lanky sort that are like slo-mo fireworks, growing, growing, then bursting forth with a show of color. My backyard is filled with them, and I make a point of going out there not only to appreciate their extraordinary work, but also to see what sorts of insects they attract. Achieve a certain stillness, forget all the other things left undone, and a whole new world may open up. In its own miniature way, insect life can be as surprising and compelling as a trip to exotic lands.

Butterflies are a good entry point. Mimi, a friend of this blog, sent me an email, excited about having seen a common wood nymph. She didn't have a camera the first time, but it returned and she was able to get a photo with her phone. Thanks, Mimi! She noted that it was hanging out around the black-eyed susans, morning glories and beebalm, and that the host plant is purple top, a common native grass in our fields.

I haven't seen a wood nymph, but have had visits from a common buckeye, maybe because we have bottlebrush buckeyes in the garden. This one's visiting a boneset, a plant that hosts a whole ecosystem of insects and spiders this time of year.

The upswing in monarch numbers has created more opportunities for magical moments. (This one's visiting ironweed.) Their flight is extraordinary to watch. There's the strength, speed and agility they display when chasing each other, and then there's the way they navigate a garden. A couple evenings ago, one came and stayed awhile. The garden surrounds our patch of grass, so to stand on the lawn and watch a monarch weaving in and out and over the flowered landscape, seeming to check out every plant yet rarely landing and then just for a sip, is like standing at the center of a merry go round. There's a whimsical, carnival ride quality to its flight, as it darts, then coasts, then darts again, changing direction on a dime. It flies with extraordinary confidence, yet seems unsure where it wants to go. This may simply be a matter of my not understanding its motivations. Whatever its aims, there's a feeling of blessing when a monarch comes to the garden. It lives up to its name, for long with the whimsy is a regal, ambassadorial quality, as it graces each plant with its presence before moving quickly on to the next.

Maybe this year I will finally learn the different sorts of swallowtails. This one appears to be a male two-tailed swallowtail, visiting a giant cup-plant in our backyard.

From the link, it looks that females have more blue.

Another magical moment this summer came unexpectedly while clearing trails at Herrontown Woods of debris. Deep in the woods, I lifted a stick and up flew what seemed like a large moth, the size of a monarch but white, pale like a luna moth but squarish in overall shape. It flew up into the canopy and disappeared. Its presence was reassuring, a sign that something of nature's depth persists in our altered world.

August's Peak Bloom of Native Wildflowers

It's been gratifying lately to hear testimonials from friends and acquaintances about the joy they've found in replacing some of their lawn with wildflowers. Though we have a few non-native flowers in the garden, there's a predominance of local genotypes of native wildflowers found growing wild in Princeton. The ones shown here are well adapted for wet ground, so have flourished in this summer's consistently recurrent rains. Here are some photos from the peak bloom in August, when the garden was positively rocking with flowers.

Autumn Helenium - Helenium autumnale

Front to back: Cutleaf coneflower, jewelweed, wild senna, Joe Pye Weed

Front to back: Boneset, rosemallow hibiscus, Joe Pye Weed, boneset, wild senna

Ironweed (Vernonia noveboracensis), Boneset (Eupatorium perfoliatum)

A mix of Joe Pye Weed and cutleaf coneflower (Rudbeckia laciniata)

RoseMallow Hibiscus (Hibiscus moscheutos)

Wild senna (Senna hebecarpa)

Hibiscus and cutleaf coneflower

Cutleaf coneflower, Hibiscus moscheutos, Joe Pye Weed

Boneset, Hibiscus, Joe Pye Weed