Friday, May 20, 2016

Winter Wren

The symphony of spring grows richer every day. Stepping out my front door this morning, a blast of birdsong overwhelmed my senses. The translucent, glowing greens and pinks of newborn leaves were muted by low, gray skies, but the warblers’ songs lit up my brain with a rainbow of synesthesia.

The upward buzz of the northern parula, who just arrived on May 12, (four days later than in 2015) sounds blue-gray with yellow and orange highlights. The sweet warble of a Blackburnian warbler sounds blaze orange as it ends in a high pitch I can barely hear. The “I, am, black-and-green” song of the black-throated green warbler sounds (what else?) like alternating dashes of black and olive.

Ok, so maybe I don’t have synesthesia, maybe it’s only that the bird songs trigger their photos in my mind, but the dreary morning felt decidedly colorful with the addition of so many perky songs.

These warblers are not known for being quiet. And yet, when the winter wren chimed in with his ringing, clear stream of tinkling notes, the other songs faded into a background jumble. This four-inch-long, one-half-ounce, drab-brown bird of the forest floor can sing with 10 times more power than a crowing rooster per unit weight. He’s been singing here for weeks now (only needing to migrate from the southern U.S.), and—although I’m excited for the new arrivals—his song still gives me a thrill.

Partly, I (and the lady wrens) am drawn to him by the power of his song, which can last up to 8 seconds as he bellows notes while both exhaling and inhaling. Party, I’m intrigued by the mystique of this tiny, well-camouflaged bird that spends his time scurrying through the underbrush with mouse-like hops. The scientific name of the winter wren (Troglodytes hiemalis) means winter-loving cave-dweller, but their caves are hollows and cavities in dead and fallen trees.

What do they look like?  A little brown blur that sometimes congeals into a short, perky, twitching tail. Only through the patience of photographers do I know that they have tiny, white checkers on their brown background, a white eyebrow, and light-brown legs.

My favorite birds are the ones who kept me company during my transient years, when I worked back and forth across the county from California to Maine. I didn’t grow up hearing winter wrens in Iowa (house wrens are more common there). I first knowingly heard one in the Boundary Waters of northern Minnesota, which automatically endeared them to my heart. On still mornings, their energetic songs would resound across glassy lakes.

When I moved to the redwoods of California, my morning jogging route took me right past the territory of a wren near a tiny stream. They love riparian areas with tangled underbrush. It was exciting—in such a drastically different forest—to hear a bird I recognized easily. I was also thrilled to hear the familiar voices of song sparrows while we took kids tide-pooling along the ocean.

The song sparrows didn’t sound quite like the ones I was used to back east, although their tone and cadence were quite identifiable. It’s well known that many birds, like people, have regional variations in their songs. A Minnesota friend who recently headed to West Virginia for a birding trip joked that she’d be hearing warblers with southern accents.

The winter wren song sounds like such a jumble to me that I can’t hear the regional variation. The lady wrens can hear it, though. Several years ago, a couple scientists set out to study the variations in several subspecies of winter wrens across the country. Birders had already noted that the wrens in the eastern U.S. sound more like wrens in England, and the western wrens share more characteristics with their colleagues from Siberia. They are a widely distributed species!

Or are they? Where the eastern and western types meet in eastern British Columbia, they hold neighboring territories. The males will respond to any wren’s song with territorial aggression, but the females only mate with males who sing the appropriate song. I’ve tried to hear the difference, but the nuances are lost on me. Only by looking at sonograms (technological synesthesia!) can I be as discerning as those lady wrens. You can see them for yourself, and read an excellent summary of the research at: www.slybird.blogspot.com/2008/07/winter-wren-is-multiple-species.html.

The discriminating taste of those female wrens seems to be all that’s keeping the two types from hybridizing. Scientists call this a “prezygotic barrier to gene flow,” because it prevents mating in the first place. Mating would actually result in fertile offspring, should it occur. This seems tenuous, but it is a strong enough divide that in 2010, scientists classified the birds as separate species: the Pacific wren and our winter wren. England and Europe also get their own species of winter wren, which, as the only wren outside of North America, they just call a “wren.”

And, seeing as how I wouldn’t last a minute trying to be a discerning lady wren, I will just call him a lovely sign of spring.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” is now open.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

Winter wrens are tiny, energetic birds of the forest floor. Ounce for ounce, they produce more sound than a rooster!  Photo by Paul Stein, Creative Commons

Friday, May 13, 2016

Spring Phenology

Birdsong and sunshine poured through open windows this morning, wafted in on a warm breeze. It was the distinctive call of a black-throated green warbler that finally lured me outside. “Zee-zee-zee zoot-zee” he shouted. “This is my territory and don’t forget it!” “Welcome home!” I felt like yelling back.

Several other melodies joined his refrain: the trill of a yellow-rumped warbler (a song I’ve been hearing for a few weeks already); the “Hey Sweetie” of a black-capped chickadee (I’ve been hearing that since January); and the tinkling stream of clear notes bellowed out by a winter wren with incredible breath control and no desire to let you get a word in edgewise. A pair of phoebes, and a few other mystery birds, also contributed their verses to the epic ballad of spring.

As I scanned the treetops to catch a glimpse of the feathered minstrels, I noticed with dismay that the maple trees were glowing brightly with tiny, translucent baby leaves among big clusters of dangling flowers. New life is beautiful, but leaf-out makes birding that much harder. I also heaved a sigh at the swarm of freshly-hatched black flies vying for my blood. Some signs of spring are not so pleasant.

It’s good for the migrating warblers, though, that the insects (and food for the insects) the birds need to eat are hatched and/or growing. When the long-distance migrant birds react to changing day length in South America and start their journey north, they have no way of knowing what weather will await them on the next continent. If we have an early spring up here, they can’t get bumped up to an earlier flight. If we have a late spring, they don’t get a text notifying them that their flight has been delayed.

These long-distance migrants tend to arrive like clockwork each spring, with very little change in their arrival dates. What variability occurs is mediated by the weather. As the birds head toward their breeding grounds, storms and lack of food will slow them down in a late spring, while favorable conditions will encourage steady progress north in an early spring.

While the weather this spring has been lovely for a few weeks now, this is the first morning I’ve heard the black-throated green warbler, who started its journey in Central America. The yellow-rumped warblers (here for a while now) may have only been wintering in the southern U.S. The blackburnian warbler (a striking, bright-orange firecracker) is still on its even longer journey from South America. It will probably arrive on about the same day it did in 2013 (May 15) even though that was the year I went cross-country skiing for my 50th day of the year on May 4.

In the meantime, the plants (who can’t go south for the winter) are controlled more closely by spring temperatures—although some regulation by day length plays a role in protecting them from blooming during a January thaw. I just photographed a plethora of spring flowers at St. Peter’s Dome. On Mother’s Day weekend 2013, I was snowed on while searching out a few spikes of furled leaves just emerging along that trail.

2013 was a great year for birding, though, because the birds came back all at once before the trees had a chance to leaf out. Visibility was amazing! Food-finding was probably a challenge for the birds, though, since local insects are also more responsive to temperature than day length.

Spring weather is always variable, but as climate change strengthens, the variability will trend earlier. Short-distance migrants might be able to shift their patterns and stay in sync with plants and insects on their breeding grounds. Researchers have found that the adaptation doesn’t happen within individuals, though. Individual birds arrive at the same time, year after year. Instead, natural selection favors the birds that are programmed to arrive earlier. They have more babies with similar, early genes, while the genes of their late-arriving peers go back to the dust.

I’ve seen a similar sentiment in a political meme floating around the internet right now, a quote by Arturo Albergati: "People don't change their minds. They die, and are replaced by people with different opinions.” While this seems a little morbid as I stand surrounded by glowing, singing, flowering, buzzing life in the most vivid season of the year, that adaptation through natural selection is actually a key to the future of life.

Observing seasonal events is also known as phenology. Come visit the Museum’s brand-new exhibit about phenology: “Nature’s Calendar: Signs of the Seasons” to learn more! Check our Calendar of Events for phenology journaling programs to inspire you to record seasonal events from year to year.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” is now open.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

Birders are often torn in spring. We want the migrants to have enough food when they pass through or arrive on territories, but we also prefer to be out with the woods unaccompanied by the birds' food source: black flies and mosquitoes. In addition, once tree leaves expand, birds become harder to see. Photo by Emily Stone. 
(I think this is a house finch. What do you think?)

Yellow-rumped warblers have been vocal and visible for several weeks already. He's so handsome!!! Photo by Emily Stone -- from a moving canoe!



Friday, May 6, 2016

False Morels

A birch twig tinkled musically in my spokes as I cruised along a mountain bike trail on opening day. Winter winds had sprinkled debris liberally over the ground, and one stick or another was caught noisily in my wheel for most of the ride. Peepers and chorus frogs rounded out this aria of the Symphony of Spring.

This particular twig wasn’t falling out on its own, so I stopped briefly to help it on its way. As I planted my toe on the ground for balance, an odd, brain-like shape next to it caught my eye. The brownish lump would have perfectly matched the “burnt sienna” crayon in my 96-color set from third grade. I always loved that color.

As an identification started to coalesce in my subconscious, I picked up the mass. Just as I expected, the cool, smooth, mushroom cap crumbled in my grasp. The convoluted undulations of the cap became shards on the ground, and I was left holding the stouter, paler stem.

While most mushroom fanatics rave over the spring crop of morels, and even novices who don’t pay attention to any other mushroom sauté that holy grail in butter and garlic, all I ever find are these false morels. These early spring mushrooms (sometimes sprouting under melting snow) grow on sandy soil under pine trees and seem to prefer disturbed places, such as trailsides.

I know there are true morels near Cable—but I’ve never seen one. (And no one will tell me where to find them, either!)

While the convoluted cap of this imposter looks superficially like morels, it is easy (and important) to tell them apart. For one, the lumps on the caps of false morels bulge outward. On true morels, the texture is formed by pits sinking inward. When sliced in half, one discovers that the cap of a true morel is fused along the entire length of a hollow stem. In contrast, the cap of a false morel is attached only at the top of the stem, and the stem itself is filled with either mushroom flesh or cottony mycelia.

I know how tempting it is to make a “hopeful” identification when you really want to find a particular species. A few years ago, I saw a lumpy mushroom cap hiding among spring flowers, and exclaimed “morel!” before looking more closely. Luckily I didn’t continue to trick myself into believing in a wrong ID. Once I pulled apart the loosely attached cap and non-hollow stem, its true identity was obvious. With any wild edibles, hopeful IDs can be dangerous.

While many people have eaten false morels, they are associated with two to four per cent of all mushroom fatalities in Europe. Reportedly, their toxins can be removed by a stringent regimen of drying, boiling, rinsing, and boiling again, and they are considered a delicacy in Finland, Bulgaria and Spain. I know a Russian who eats them regularly! In contrast, Germany, Sweden, and Switzerland restrict the sales of false morels.

One of the hazards of consuming false morels is that the toxin levels vary widely among populations of mushrooms. Some areas seem to grow “safer” mushrooms than others. Nobody knows how toxic any false morel will be in any location. While the false morel in North America is also known as Gyromitra esculenta, it may not even be the same species as the European false morel.

So was I touching poison when I crumbled that lump along the mountain bike trail?
Well, no. Touching a false morel won’t hurt you. The problem comes when you eat it, or inhale the steam from cooking. Their active toxin is called gyromitrin, and your body metabolizes it into monomethylhydrazine, a chemical found in rocket fuel. That is not something you want in your stomach.

Boiling will begin to evaporate the gyromitrin, which smells chocolaty, but is not good to inhale. Gyromitrin destroys red blood cells. It damages your liver and gut. And it doesn’t take effect immediately. It takes 6 to 12 hours to develop symptoms. But by the time the nausea, cramps, vomiting, diarrhea, and fever begin, there’s not much you can do. Most people receive supportive care and recover after several days of illness. In other cases, convulsions lead to a coma and death.

Even if you don’t get sick from eating a single helping of false morels the next batch might be more toxic, and repeated exposure to the toxin causes cancer in mice, and maybe us, too.

All that drama is contained in a small, lumpy packet colored a beautiful shade of brown.

Musical twig removed, I continued pedaling down the trail. Before I could swerve, two more false morels appeared in the center of the trail, and then shattered under my tires into a burnt sienna mess.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” is now open.


Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

False morel mushrooms look only superficially like the edible true morels. It is important to look closely, because an incorrect identification could make you uncomfortable. Nonetheless, they are fun to see in early spring!
Photo by Emily Stone.

Friday, April 29, 2016

Queens of Spring

The gentle sound of waves lapping at the shore tugged me toward the lake. Finally, the last sheets of ice in my little bay had melted away under the persistent caress of a warm breeze. Late afternoon sunshine prickled the back of my neck. A dead branch lay across the trail, nestled in the moldering leaf litter, victim of the winter winds. As I stooped to pick it up, a bit of color caught my eye. Zooming low above the moss was a big, fuzzy, bumble bee.

I didn’t react quick enough to stop my momentum, so the flying branch scared off the flying bee. I did get a brief glimpse of a bright orange stripe in the middle of the classic black and yellow body.

I’ve seen a bee like this before, as it was wallowing in the bounty of summer on a dazzling prairie blazing star flower. Somehow I came to identify it as Bombus ternarius, a tri-colored bumble bee. The landscape on this April day, although warm and sprouting, was a far cry from that flower-filled August field. Most bees don’t fly this late in the day, even in summer.

Bumble bees, I knew, are able to fly at colder temperatures than many other insects. Flight muscles don’t work when they’re too cold, but the limits of bumble bee flight are lower than most. In addition, they raise their body temperature above the ambient temperature using a few neat tricks.

First, bumble bees readily absorb what little sunshine peeks through the spring clouds. Then they generate their own heat by shivering muscles without flapping their wings. It can take 5 minutes of shivering to raise their muscle temperature to the required 86 degrees when the air temperature is 55. Finally, the thick fuzz that covers their bodies insulates and helps retain their hard-earned heat.

All these adaptations mean that bumble bees can be active earlier in the spring, earlier and later in the day, and in more adverse weather conditions than honey bees and other not-quite-so-hairy bees.

Still, this early in the season, I must have been in the presence of a queen. Each fall the old queen bumble bees and all the male bees die in the cold, while newly fertilized queens find a safe, underground place to overwinter.  When they emerge in the spring, the queens are on their own for at least 5 weeks, until the eggs they lay become their  hard-working colony.

While you may imagine that all bees nest in a hive or hollow tree like the European honey bees we use to pollinate our crops, our native bumble bees tend to house their colonies in abandoned mouse nests or other underground burrows. The burrows are sheltered from the weather and pre-insulated with grass, thistle-down, and mouse fur. Many other types of native bees are solitary and don’t form colonies at all.

It takes a lot of fuel to keep a big bumble bee buzzing, so the queens will often try to locate their nest near a food source. Near this lakeshore, the only flowers I’d seen were on willows, but elsewhere, patches of Dutchman’s breeches are said to be a draw. These oddly-shaped white flowers are consistently some of the first blooms I spot in the woods.

Not just any insect has the strength and tongue length to forage for nectar in these little pantaloon-shaped flowers, though. The queen bee grabs onto one of the white flowers, and the one next to it too, for stability. Then she’ll burrow her tongue first and then her head into the flower and angle toward one of the nectar spurs. Throughout this process, the flower’s anthers brush pollen onto her head, thorax, and forelegs. Smaller bees can’t quite pry open the petals to access the juice bar inside and they sometimes cheat by chewing a hole in the nectar spurs.

While the plant’s goal for the pollen for is for it to travel to the female parts of another flower, the queen bee uses some of it—and nectar, too—to fill a tiny honey pot inside her burrow. This food will sustain her while she broods her nest. When the pantry is stocked, she lays her eggs. After four days the eggs hatch and she feeds the larvae on more nectar and pollen while they grow. After two weeks as larvae and two more as pupae, the queen’s hard work pays off when her daughters emerge as adults—full grown and ready to work.

Queen bumble bees are especially important pollinators in early spring, but throughout the year, Wisconsin’s thirteen species of native bumble bees contribute mightily by pollinating native plants as well as crops like tomatoes, peppers, squash, cranberries, and blueberries. Their capacity to fly in cooler temperatures and ability to muscle into certain flowers make them invaluable.

But bumble bees face the same threats as honey bees: parasites, pathogens, pesticides, invasive species, climate change, and habitat loss, among others. There’s quite a buzz around bees these days, and when you learn about them, it’s not hard to understand why. They are truly the queens of spring.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” will open May 1, 2016.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.


Tricoloured bumble bees are a brightly colored and easily recognizable native bumble bee. This time of year, until at least May, if you see one you can be sure that she’s a queen. Later in the summer you’ll mostly like see her worker bee daughters gathering provisions for the nest (like this one on a prairie blazing star flower). Male bees gather nectar for themselves, but don’t help provision the nest. Photo by Emily Stone.

Friday, April 22, 2016

The Symphony of Spring

A big truck rumbled by as I squeezed the brake levers and guided my bike onto the shoulder. The wonderfully warm, sunny afternoon had lured me out on an adventure, and my first stop was this small, roadside wetland. With a southwest exposure, this marsh thaws a day or too sooner than the one by my house, and I head here each spring to listen for the first frogs.

As the truck’s noise faded, silence fell over the forest. Peaceful, yes, but not what I’d hoped for. Could the wood frogs still be waking up? It does take them a little while to recover from being frozen all winter. With the arrival of warm temperatures, wood frogs thaw from the inside out.

Recovery is relatively rapid—especially considering what they’ve been through—but not instant. The frog’s heart starts beating before they are fully thawed. Breathing resumes soon after, and circulation begins as soon as their blood melts. That doesn’t mean the frog is ready to hop off into the sunset, however. It takes more than five hours for their leg muscles to regain some function and up to 24 hours for the frogs to exhibit normal body postures and coordinated muscle functions.

A couple days later, their mating drive kicks in. That’s what I stood there hoping for, in the silent woods. Then, from the back corner of the wetland came a soft quack. And another. Then a second frog called softly from another shore, and a third chimed in tentatively from near the road. From there, the chorus crescendoed until a cacophony of quacks, chuckles, and clucks echoed through the woods.

For the next few weeks, this wood frog choir will continue their performance whenever the temperature rises near 50 degrees and above. It is mostly males who call, and the impassioned sound serves to attract females to their pond. The more females their calling can attract, the better chance each male has of finding a mate.

As frogs arrive at the pond and mill around, eager males will search for a mate. They can’t see or smell a difference between females and other males, though. Instead, a male frog hugs another frog from behind and around its waist. Fellow males, identified by their slim waist, give a loud croak and are released. A slender female, who has already released her eggs, also gets a pass. But when a male frog grips a plump female—chock full of eggs—he hooks his thumbs around in front of her and doesn’t let go. This is called “amplexus.”

From there, the female deposits her eggs in a floating mass and he fertilizes them as they emerge from her body. Many wood frogs in a pool may lay their eggs together. The earliest breeders benefit from their eggs being in the center of the mass where they absorb heat, develop faster, and gain protection from predators. Each individual’s 10 cm diameter egg mass contains from 1000 to 3000 eggs.

Eggs laid now, in the cold infancy of spring, will mature slowly, over the course of a month. Later in the spring, when the water has warmed, the eggs may hatch in only 10 to 14 days. The amphibious parents have completed their responsibilities, though. They don’t stick around to provide care, cheer at baseball games, pay for dance lessons…

…Or teach their little tadpoles to ride a bike. Thankfully, I’m human!

As the frog chorus reverberated, I swung back onto my bike and continued around the lake. Wood frogs were only the beginning.

Not far from where I’d recently seen two otters on the ice, I spotted a sleek pair of loons in open water. With my ears now tuned in, the jingle bell chorus of spring peepers became apparent everywhere. Three stunning, black-and-white osprey perched on top of their nest platform (three!?) and swooped into flight as I approached. A bright orange fox with sleek new fur bounded through the ditch. As I slowed to look for more loons from a short bridge, the clear whistle of a song sparrow reached my ears.

All along the road, frogs croaked and peeped, robins whinnied, juncos trilled, and geese honked. Silence has gone out of style. Let the symphony of spring commence!

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” will open May 1, 2016.


Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

These remarkably terrestrial frogs spend most of the year in the woods, but wood frogs migrate short distances to woodland pools for mating in the spring. They are distinguished by their rakish black mask. 
Photo by Emily Stone.

Friday, April 15, 2016

Out on a Limb

Broken branches littered the road from a thrashing wind and rain storm the previous night. I paused occasionally from my walk to pull the bigger ones out of the way so they wouldn’t surprise unsuspecting drivers on the winding gravel road. After dragging a red maple branch—replete with swelling, crimson buds—to the shoulder, I noticed that the soggy gravel was still covered with the brightly-colored clusters.

Had all these buds been knocked off in the storm, too? But why would they remain united in their twig-tip clusters? I picked one up to examine it more closely. Two rings of buds encircled the tiny shoot, and the twig showed a neatly-clipped end. Something had bitten the twig off of the tree. The buds looked intact, though. Why would some creature go to so much effort, and then let it all fall to the ground?

I, too, dropped the cluster as I continued on my walk, but the problem still bugged me. Porcupines often feed on “nip twigs” like this—snipping a branch, then turning it around to access the edible parts—but a porcupine would have nibbled the buds off. Plus, I recently learned that porcupines almost never eat red maples because the plant contains too many acidic tannins as a defense. I’ve seen squirrels feeding on hemlock and spruce buds in this manner, too. But each little spikey green nip twig I recover from that snacking technique is missing its nutrient-packed terminal buds.

When the loop of my walk brought me back to the patch of maple buds on the road, I decided to look more closely. I’m glad I did. Although the buds looked undamaged from afar, when I looked closer, I could see that most of the buds had been gutted. The outer bud scales—bright red with white margins—were still mostly intact, but a single hole in the bud led to a hollow center. Perhaps the muncher was avoiding toxic tannins by only eating the tender embryonic leaves and flowers, and not their tough, protective covering.

A quick internet search revealed that yes; red squirrels, gray squirrels, flying squirrels, and fox squirrels all will eat red maple buds in the spring. No source mentioned that they hollow out the buds, but that’s I observed, and it makes sense as a technique to avoid excess tannins. If that’s true, then I would guess that squirrels have an advantage over porcupines in exploiting this niche—while squirrel teeth might be small enough to scoop the sweet centers out of tiny buds, porcupine teeth most likely are not.

Squirrels must be crafty in this is a hungry time of year, when their supply of fall nuts and seeds has run low, they need energy for breeding season, and extended cold has slowed the arrival of a spring bonanza. Soon (we hope) they will have more food in form of willow and aspen catkins, maple flowers, maple seeds, and even baby birds. Until then, I guess we’re all on the same boat…er, branch…waiting anxiously for spring.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” will open May 3, 2016.


Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

These nipped-off clusters of red maple buds present a mystery to curious naturalists. My guess is that squirrels scooped out the tasty baby leaves inside the tough bud scales. Have you ever seen the culprit at work? Photo by Emily Stone.

Friday, April 8, 2016

Slushy Cold and Palm Trees

Slushy cold drink in hand, I took a deep breath and looked up from my book. Rows and rows of beach chairs stretched out in front of the one I had claimed, their geometric arrangement accented by regularly spaced palm trees. Through the trunks, past the white sand, and between brightly colored bathing suits, turquoise waves sparkled in the sun.

I was grateful for the shade of the palms (I think they were coconut palms), since the warm afternoon sun would have surely boiled my winter-thickened blood and crisped my pale skin to crimson. But the trees bothered me, too. Usually on vacation (usually in the Boundary Waters), I contemplate the tenacity of gnarled jack pines whose resolute  roots find the ingredients for life wedged deep inside bedrock cracks. How did the resort ever get palms to grow in pure, salty sand?

While my vacation in Playa del Carmen, Mexico, was filled with all the usual activities, I also experienced a fair amount of frustration. With little prior knowledge of tropical natural history (I tend to head north for trips), and no nature guides (paper or human) on hand, I felt lost. Next time I’ll do it differently, I resolved, but this time I still had to deal with the unusual experience of not understanding my environment.

Arriving home to internet access, I had many questions, but the problem of palm trees stood out. I knew they weren’t like maples or oaks, but why and how?

The essential difference is that maples, and many flowering plants that we’re used to, are dicots. When their seeds sprout, they produce a tiny pair of baby leaves, or cotyledons. Palms are monocots, and along with grasses, lilies, and asparagus, they only produce one cotyledon when their seeds sprout. The number of seed leaves is just the beginning—an easily visible character that actually indicates much deeper differences.

For one, the roots of palm trees don’t go deep. Instead of a sturdy taproot and woody lateral roots gripping deep into the bedrock crack, palm trees have a mass of small, non-woody roots that begin low on their trunk in the “root initiation zone” and extend to form a dense mat in the upper foot of soil. Instead of tapering toward the end, the roots of a palm stay the same diameter throughout their length. The roots visible around the lower trunk of many trees reminded me of a bowl of thick spaghetti noodles.

As it turns out, this root structure makes palm trees relatively easy to transplant, which explains how the resort could build itself a ready-made shade structure of mature trees. Not only are the root mats easy to manage, the trees have their own insurance against transplant shock.

Every year I cross my fingers when my tomatoes droop for their first days in the garden, as they struggle to get roots to water and restore turgor pressure to their cells. Palm trees can live off the water and carbohydrates stored in their trunks while the roots regrow.

That palm trunk arises from a single apical meristem, or cluster of undifferentiated cells where growth can take place. In a maple tree, meristems allow for branching, twig growth, and much more. A palm tree has no capacity for branching, and grows straight up, with its leaves also originating from the single meristem at the top of the stem. Old leaf bases cluster around the meristem in a bristly beard, which offers it some protection against cold, disease, trauma. If the apical meristem is damaged, the whole tree will die.

Maple trees also have a lateral meristem—the cambium—which grows new cells around the stem each year, thickening the trunk and forming the tree rings we know so well. Though stiff and sturdy, palm trunks aren’t truly made of wood, and the cells aren’t arranged in rings. Instead, its vascular system of xylem and phloem bundles is dispersed throughout the stem with no ring-like structure. The stem grows slightly wider and stronger, mostly through the thickening and strengthening of these cells as they age.

Because of the dispersed nature of palm trees’ vascular systems, they aren’t susceptible to girdling. In a maple tree, the vascular system is just under the bark, and if you cut it all the way around, water can’t flow, and the tree dies. With dispersed vascular bundles, water would simply continue to flow elsewhere inside the palm’s trunk. The tree might die of disease from such an injury, though. Palm trees don’t have the ability to grow scar tissue or repair damages, so any break in the bark-like cortex may allow in disease. In contrast, as maple sugaring operations prepare to pull their taps, the operators know that this year’s hole will soon fade under a healing scar.

The differences between sunny Mexico and spring in Wisconsin are extensive, and fun to think about. I’m glad to be home, but I do wish that the slush would stay placidly in my cup instead of falling from the sky.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” will open May 1, 2016.


Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

Palm trees provide shade just like our maple trees, but they grow very differently.
Photo by Emily Stone.