Common Butterwort Eats Bugs

I met a new friend this spring, and I’ve been heading up north to visit them every chance I get. We didn’t meet online exactly, but I did use an app to figure out their location. You see, I read about them over the winter, and just had to find out more about their life! They are a little odd – they supplement their diet with insects and make an unusual kind of yogurt – and they may not be hanging out this far south for very much longer.

Being a botany nerd, I call this new friend of mine Pinguicula vulgaris, a plant also known as Common Butterwort.

I first encountered butterwort in a wonderful book called North Shore: A Natural History of Minnesota's Superior Coast, by Chel Anderson and Adelheid Fischer. Although I bought the book at an author talk when it first came out in 2015, I’m still not quite finished. Yet every time I sit down to read, I discover something new! This book was the first place I learned that the leaves of a pitcher plant cradle an entire community of life, which I’ve now written and taught about too many times to count.

“Defying the ravages of waves and ice to this day are such rare prizes as butterworts, whose pinwheels of pale green leaves cling like glistening starfish to the wet faces of the bedrock shore,” Anderson and Fischer wrote. Amazing! Now this was someone I had to meet. “Find butterwort” appeared in bold text on my mental bucket list.

I put down the book and picked up my phone. Using the “Explore” tab in my iNaturalist app, I quickly pulled up a map with little green pins dotting the shore of Lake Superior from Two Harbors up to Grand Portage, all around the Canadian North Shore, and over into Michigan as well. Zooming even farther out (iNaturalist data is global!!!) I discovered even more pins – locations where other naturalists have made observations of this same plant – throughout Washington, Alaska, Canada, Greenland, Iceland, the United Kingdom, and all over Europe. Common Butterwort is circumboreal, and occurs all around the top of the globe. Northern Minnesota and Wisconsin are just beyond the southern edge of this ecoregion.

iNaturalist map of Common Butterwort observations. inaturalist.org

On a late May trip to Grand Marais, MN, I poked around on the bedrock trails of Artist’s Point to see what I could find. 

Artist's Point, Grand Marais, MN

The first rare plants to catch my eye were Bird’s Eye Primrose, a species I’d first admired in Alaska. Nestled into the mosses nearby were the small rosettes of roundly triangular, chartreuse leaves of butterwort. Sweet! I knew it was too early for flowers, but I was excited to see deep purple buds rising on little stalks from the center of many of the rosettes.

I also noticed a smattering of tiny bugs stuck to the leaves. Take that, mosquitoes!

Looking closely, you can see several unfortunate insects who have become mired in the stick excretions of this Common Butterwort leaf. They will be digested and their nutrients absorbed through special pores. Photos by Emily Stone

Like pitcher plants, Common Butterwort is carnivorous. Their leaves are covered with little stalks, each tipped with a tiny drop of sticky liquid, not unlike the leaves of sundew, another carnivorous plant. Small insects get stuck on these drops, and their struggles stimulate the leaf to curl in on itself and release digestive enzymes. To prevent the insects from rotting – i.e. getting eaten by bacteria – while they are being digested by the plant, butterwort also releases antibacterial chemicals.

Although the name butterwort comes from the greasy look the sticky glands give to their leaves, the enzymes on their leaves are able to curdle milk. What? A plant who can make cheese? But it makes sense. Rennet, a key component of cheesemaking, is sourced from the stomachs of young cows, sheep, or goats. These carnivorous leaves are essentially exposed stomachs. The Swedes use butterwort leaves to make filmjölk, a breakfast food similar to yogurt.

In order to absorb the nitrogen and phosphorous they need from their insect prey, butterworts must open pores on their leaf surfaces. This puts them in danger of drying out, which is why butterworts grow in cool, humid places, and why they occur only in a few specialized habitats this far south.

Two weeks later, in early June, I returned to Artist’s Point on one of those cool, damp days so typical of Grand Marais. Just as I’d hoped, the buds had opened to reveal lovely purple flowers – similar to violets – with long nectar spurs and hairy white tongues. Only large insects could get past the hairs to reach the nectar, so the bees, butterflies, and moths who might be pollinators are also strong enough to escape death-by-leaf should they accidentally land on one.

Common Butterwort flowers have hairs guarding their long nectar spurs. This means that their pollinators can only be insects who are too big and strong to get caught on their sticky leaves. Photo by Emily Stone.

As I approached one of the neatest pockets of moss, sedges, primrose, and butterwort in a little bedrock terrarium, I was surprised to find a white square of PVC surrounding the bouquet, and a person looking intently at the plot, notebook in hand. While I didn’t know this person, I knew the type: scientist!

Someday soon I’ll tell you more about why both of these new friends were at Artist’s Point that day!

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is open with our brand-new exhibit: “Anaamaagon: Under the Snow.” Our Fall Calendar will open for registration on August 1! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

Spilled Pennies

“You’re in charge, Keir,” said Mary Ann Feist, a curator from the Wisconsin State Herbarium and organizer of the Peatland Field Course. “Ok, then I’m just going to walk in until I can’t stand it anymore,” replied Keir Wefferling, a botanist from UW-Green Bay. He began picking his way over the gnarled trunks of fallen cedars and around black pools of unknown depth. We, a group of about 20 professional and amateur botanists, followed him gingerly into the dark forest, not knowing what to expect.

Keir Wefferling, botanist and curator from the University of Wisconsin-Green Bay, center, explains moss diversity to a group in the middle of a white cedar swamp. Photo by Emily Stone.

After only about 20 feet, Keir called out, “I can’t stand it! There’s incredible diversity right here, we have to stop!” We all gathered in a loose circle, shifting our feet to find solid ground among hummocks of rotten and less-rotten wood and mysterious wet hollows. Each of these surfaces was plush with a carpet of moss.

Keir, who specializes in moss, passed around tuft after tuft of green Dr. Seussian inventions. The scientific names he gave with each sample slipped through my brain in a fog of unspellable syllables. I admired each one eagerly, though, in awe of the kaleidoscope of leaf shapes, textures, patterns, and colors.

I was crouched down, admiring the round, glistening leaves of a unique moss sprinkled in a thick jumble across a small bowl between cedar roots, when Keir finally spoke words I recognized. “And here’s some spilled penny moss…” I couldn’t even see the specimen he held up, but I knew he’d just named my lovely, shiny friend.

Spilled penny moss has distinctive round leaves. We found this beauty growing in a shallow pool of water under cedar trees. Photo by Emily Stone

It's amazing close-up, too!

A few minutes later, from a different wet spot, Keir lifted another moss with a fun common name: drowned kitten moss. The scientific name of this one is Sphagnum cuspidatum, he lectured. The sphagnum part is easy for me to remember, because sphagnum mosses are common in bogs and fens. They have a particular look about them, with a fuzzy head of compact leaves, and then a long stem with drooping leaves. When they are all packed together in a mat, they look quite soft and inviting.

Except for drowned kitten moss. They grow in the lowest, wettest spots and look as bedraggled as their name suggests, especially when you lift them out of the water. Sad as they may appear, this is their preferred habitat – their happy place, if you will – with just the right mix of water, acid, nutrients, sun, and shade. Their dust-like, windborne spores allow them to grow in wet spots around the world. They are found in Great Britain, Norway, Sweden, Colombia, and the Northeastern United States.

Drown kitten moss, a species of Sphagnum, has a very memorable common name. 

Photo by Emily Stone.

It took a while for the group to make our way back out of this Northern Wisconsin cedar swamp. Northern white cedars grow where cold, clean groundwater flows horizontally near the soil surface, and plants often create quite a thicket. The trees have the advantage of not needing to travel through their own tangled habitat. We all held up forearms to guard our eyes against sharp twigs; several people put a leg through a rotting log; others cautiously found different routes; and then there were the mosses, and flowers, and shrubs, and spiders, and bumblebees, to distract us, too!

After supper, lovingly prepared by a team of Cable Natural History Museum volunteers, and served at the Gatehouse at the Forest Lodge Educational Campus where the course was based, we gathered in the Great Hall to look more closely at the moss samples collected from our field sites.

Keir used a razor blade to cut tiny slices of moss leaves, then placed them onto a microscope slide. Once he brought the specimen into focus, I removed the microscope’s eyepiece and replaced it with a tiny camera hooked up to my computer. Instantly, the delicate line of leaf cells Keir had been looking at popped up on the big screen at the front of the room. We gasped in awe at the delicate beauty.

This delicate chain is one layer of moss cells sliced from a tiny leaf and viewed through a microscope. Photo by Emily Stone and Keir Wefferling.

A chain of clear, round cells was strung on a thread of green. The clear cells were dead, and their job was to soak up water. The green cells were full of chloroplasts, the photosynthesizing, sugar-producing organs of the mosses.

A moss leaf viewed through a microscope. Photo by Emily Stone and Keir Wefferling.

We oohed and ahhhed at the macramé-like patterns of moss cells illuminated on the screen. For one species, we zoomed and zoomed in again with the microscope until we could see that the cell walls were lined with tiny protrusions, like goosebumps on your skin.

The interconnected mesh of moss cells was reminiscent of the bigger ecological web that these little beings inhabit. The glacial history shaped the landscape; our current cool, wet climate provides the water; and the cedar trees protect the mosses with their deep shade. Pools of water in between the cedars’ roots shape an even smaller landscape and microclimate.

A moss leaf viewed through a microscope. Photo by Emily Stone and Keir Wefferling.

Sometimes, the mind-boggling diversity of our world makes my brain feel a little like a drowned kitten. More often I feel like I’ve discovered a world glittering with uncountable pennies that some giant spilled across the landscape in a colossal bumble, sending the tiny treasures rolling into every nook, cranny, hummock, pool, and inside every leaf of moss. Add up all these spilled pennies, and we find ourselves so surrounded by the wealth of wonder that we can hardly stand it.

Close-up of Sphagnum squarrosum. Photo by Emily Stone.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is open with our brand-new exhibit: “Anaamaagon: Under the Snow.” Our Summer Calendar of Events is open for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

Avian Anglers

Birdsong emanated from every alder thicket and treetop as we floated down the Namekagon River. The natural habitat here, protected by the National Park Service as part of the St. Croix National Scenic Riverway, is teeming with life. Although we could admire the colorful flowers and damselflies, the little singers stayed hidden in the brush. In between songs they were probably hunting caterpillars to feed to their chicks.

Far more visible were the bigger birds. The skew of a startled green heron alerted us to their presence, and we looked up in time to watch them land in a tree with their bright orange legs. With our eyes in the air, we spotted an osprey disappearing around the river bend. A kingfisher made a single rattling cry as he swooped from branch to branch in his powder-blue tux. And as I looked up from photographing damselflies, an eagle materialized in a distant white pine. No caterpillars gleaned from dense leaves would satisfy these birds. They were looking for fish.

I pretty much stopped fishing after my dad stopped untangling my line and tying my hook. The few times I’ve tried as an adult, I’ve come up empty-handed. So I have the utmost respect for osprey, who catch at least one fish for every four dives. How do they do it? Osprey, eagles, kingfishers, and green herons have adaptations that make them excellent anglers.

First, all these birds have excellent eyesight, and a third set of clear eyelids, called nictitating membranes, that close like goggles when they dive. But water is weird, and visual acuity isn’t enough. Have you ever looked at a drinking straw through a clear glass of water? To our eyes, the straw seems to kick off to one side at the surface, because the denser water bends light differently than air. This refraction makes it difficult for a human to accurately reach for something below the water surface. Somehow, these birds can compensate for refraction and aim correctly.

For kingfishers, scientists have figured out a special mechanism. Two focal points in their eyes allow kingfishers to adjust for the change in refraction between air and water as they dive after a fish. The position of these two foveae gives kingfishers monocular vision in the air (each eye is used separately) and binocular vision underwater (which allows them to judge distance).

Belted Kingfisher male, photo by Larry Stone

To hunt, ospreys, eagles, and kingfishers may perch on an overhanging branch, or hover directly above the water. Herons prefer to do their stalk-and-stab routine while standing on the ground.

Seeing below the surface doesn’t mean any of these birds want to dive super deep. They all hunt in shallow water – although shallow to an osprey is 3 feet, while shallow to a heron is 3 inches. All of their relatively short, broad tails aid them in soaring, while not getting in the way when they dive.

Eagles and ospreys, being raptors, have strong talons. Additionally, spines on their toes help them grip fish. Powerful wings allow them to lift off even when carrying several pounds of dinner.

Bald Eagle, photo by Emily Stone

The abundance of white feathers on the underside of an osprey makes it easy for us to distinguish them from eagles, and makes it harder for a fish to notice them against the bright sky. Once an osprey spots a fish, they tuck their wings and dive head-first toward the water, switching to feet first as they close in. Osprey’s longs legs mean that they don’t always go under when plunging for a fish, but if they do, their nostrils close, and oil on their feathers keep them from getting waterlogged.

Two juvenile osprey with a fish at their nest platform. Photo by Emily Stone.

As the osprey grabs hold, their outer toes reverse. This allows the osprey to grip a fish facing forward, aerodynamically, with an equal number of toes on each side of the body. Most of the fish they catch are six to thirteen inches in length, and weigh around half a pound. Their long wings beat powerfully to lift both bird and prey from the water. And then, they use their hooked beak – a trait they share with eagles and other raptors – to tear the fish into bite size pieces. Of all the raptors, ospreys are the only ones who eat almost 100% live fish.

While not raptors, kingfishers also plunge in for their prey. Unlike ospreys, their conical beak hits the water first, and pushes it aside with minimal impact or splash. Instead of tearing fish into bite-sized pieces, the kingfisher carries the perch to a perch and whacks them dead, then swallows them whole. Kingfishers, who are thirteen inches long at most, have been known to eat fish up to seven inches long. Their trick? They leave part of the fish hanging out of their beak until stomach juices digest enough of the fish that it can slide in all the way.

Green herons also employ a dagger-like beak to catch or spear fish, usually while stalking through the shallows. Green herons will place a little bit of bait, such as insects, feathers, sticks, or bread crusts, on the surface and then eat small fish who are lured in. This type of tool use is rare among birds.

Green Heron, photo by Emily Stone

As we rounded yet another bend in the river, a human angler came into view. He was standing in a riffle with his favorite tool – a fly rod – looking happy. Whether you wear feathers or khaki, the Namekagon River is a great place to catch fish!

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is open with our brand-new exhibit: “Anaamaagon: Under the Snow.” Our Summer Calendar of Events is open for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

A River Full of Life

With a quick push from shore, my old green canoe caught the current and we swept downstream on the Namekagon River. The recent rains have filled the river with more water than I’ve seen in a couple of summers, and warm days have filled the river with life.

Within minutes of launching, we surprised a doe and fawn who were feeding on a sandbar. Aquatic vegetation often contains more sodium and iron than plants in the forest. Plus, mosquitoes don’t seem to be as plentiful in the sunny river corridor as under the shady trees. I was much happier to see the deer here than jumping across the road! We cheered the little fawn on as the pair bounded across a riffle and disappeared into the brush.

Steering quickly as the river became braided into several channels, we snaked between islands of vegetation and alders reaching in from the shore. The river didn’t used to be quite so narrow here. These alders haven’t sprung back since the late winter storm a few years ago that turned many trees into archways instead of columns.

When the river widened again, bright yellow caught our eye among the emergent vegetation. Yellow iris were in full bloom! I love their sunny color, but these iris are considered invasive. They can exclude native plants, while providing few resources to our native insects and wildlife. Their dense mats of rhizomes can even trap soil and raise the land level! Plus, all parts of the plants are toxic to animals.

Yellow iris are native to Europe, where they seem to help reduce harmful bacteria and heavy metals in contaminated water. It was even observed by scientists that yellow iris were "one of the few plants flourishing after a nuclear holocaust.”

The flowers have powerful symbolism, too. They are thought to be the basis for the fleur-de-lis, the symbol of the French monarchy. The Boy Scouts of America adopted the three-petaled shape because of its similarity to the north point of a compass, and to represent the three aspects of the Scout Promise: duty to God, responsibility for self, and service to others. It’s not hard to imagine why people introduced this elegant flower into landscaping on this continent as early as the 1700s.

The Boy Scout fleur-de-lis

Just a few more bends down the river, and it was purple that caught our eye. This was the blue flag iris, which is native to the Eastern U.S. and Canada. While this iris is also toxic, and can form dense clumps, their long history in the local ecosystem means that they have relationships with plants and animals that provide habitat value and reduce their ability to take over.

The wide, stiff, leaves of the iris blended with the wide, stiff leaves of giant bur-reed nearby. Bur-reeds are some of my favorite aquatic plants because of their quirky flowers. The round, pom-pom like blossoms turn into spikey, mace-like balls of seeds once pollinated by the wind. Those seeds are food for ducks. In contrast to the two species of iris, this one species of Sparganium is native to both Europe and North America! I wonder if the ducks are responsible for spreading the seeds so widely?

Giant Bur-reed

I’d been admiring all these flowers from afar, until a patch of sparkles poked through the current. With some quick maneuvering, the canoe was soon pointed upstream near the water crowfoot flowers with the stern resting on a hummock of grass. This gave me a chance to fully admire the tiny white-petaled flowers, each with a sunny yellow cluster of pollen-filled stamens. Their leaves – submerged in the river and forming a thick mound – were finely divided and branched. I submerged my camera to capture their underwater beauty.

I couldn’t help but be distracted by all of the damselflies fluttering above the crowfoot and in the alders along the bank. Ebony jewelwings have to be some of the prettiest insects on the planet with their iridescent blue-green bodies and elegant black wings. They flit out from a twig to catch tiny gnats, and then rest demurely with their wings upright and closed. While perched, they sometimes open and close their wings quickly as a notice to other damselflies – whether competition or love interest – that they are present.

Green frogs sang us downstream, with their single, banjo-like “plunk” calls. A few mink frogs added their voices, too, like the knocking together of two marbles. Painted turtles slipped off their sunning logs as we glided past. The skew of a startled green heron alerted us to their presence, and we looked up in time to watch them land in a tree with their bright orange legs. With our eyes in the air, we spotted an osprey disappearing around the river bend. Then a fish jumped right out of the water, and we knew what the osprey had been searching for.

I’m not sure that we’d been searching for anything in particular when we decided to paddle on the Namekagon, but what we found was a river, that, in the words of Mary Oliver, is “touching every life it meets.”

Check our Instagram and Facebook Reels for videos from the day!

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is open with our brand-new exhibit: “Anaamaagon: Under the Snow.” Our Summer Calendar of Events is open for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.