Today is the International Day of Forests which means it’s the perfect day to celebrate the trees of the BWCA. The Boundary Waters are a unique mosaic of forests born out of wildfire, windstorms, logging, and the passage of time. Despite the history of disturbance, the Boundary Waters contain the largest tracts of old growth forest left in the state of Minnesota. It is also one of the last semi-intact fire regimes anywhere east of the Mississippi. As a child taking my first trips, I remember being fascinated with the trees. As my dad tried his best to keep our stern-heavy canoe straight, he would find himself bombarded with questions about every tree. “Why is that cedar leaning?” “How old are those pines?” “Why did this big pine tree blow over?” And on and on it went. And as an adult, the trees of the BWCA still fascinate me. Each species and, in fact, every individual has a story to tell of adversity and challenges overcome. Trees cannot run away from their problems the way animals or people can and, because of that, trees can actually be some of the best story tellers for those who have learned how to “listen.” They bear the scars of the world they live in. Want to know when the last fire was? Go to the trees. Want to learn stories about droughts and floods over one-hundred years ago? A tree can tell you. Want to learn about storms, heavy snowfall, strong winds, glacial deposits, soil-moisture content, wildlife populations, or how cold the winters are even if you haven’t experienced these things for yourself? To some degree, trees preserve the stories about all these things and, to the studious observer, lend a perspective of the wild world that is rich and invaluable. For this article, we’ll be covering fifteen species of trees one can find in the BWCA, some of their characteristics, which of these stories they can tell us, and where you can see some of these majestic trees for yourself. This is not an all-inclusive list. Seek out those other species for their unique contributions to the ecosystem.
Jack Pine: No species in canoe country is as directly entwined with fire as the jack pine. It has a special adaptation called serotinous cones specially adapted to only open in the heat of an intense wildfire. When a fire clears the canopy, the cones open in full sun and jack pine can completely take over the barren landscape. Simply paddle some of the areas affected by the big fires like Ham, Cavity, or Pagami and you will see the wispy tops of jack pines shooting up by 3 or 4 feet in height every year. With time, the jack pine start dying off, somewhere just past the 100 year mark. It starts with a few, maybe a wind storm topples a few rotted trees here or a drought finishes off a few there. Then they really begin aging out of the stand. By the 140-150 year mark, the majority of the jack pine have been replaced by whichever shade-tolerant species have followed. Because of the rich history of fires in this region, jack pine do remarkably well in the BWCA. In fact, the largest jack pine in the United States was found in the BWCA just a few years ago. As far as story telling goes, because they are so intimately tied to fire, they give a great estimate of when the last fire visited a specific parcel of forest. If you can estimate how old a jack pine is, or have tree rings from inside the trunk to count, you can get within twenty years or so of when a fire ripped through the landscape.
The Poplars: Like jack pine, the aspen/poplar trees of the BWCA are often connected with fire. Just take a paddle down Seagull Lake, for instance, and look for their bright green leaves shaking in the wind on fire-scoured ridge tops. When a fire scorches the canopy, the aspen are ready to grow back. The roots of an aspen tree, insulated by soil, have been tested to survive temperatures close to 1400 degrees so long as the bark doesn’t scorch. When the fire has passed, aspen can regenerate from their roots shooting up into the new open space. This adaptation also comes in handy against one of the BWCA’s other forest-killers: windstorms. Look closely at some of the stands impacted by the 1999 Fourth of Juluy blowdown in places like Kekekabic or Brule and you’ll see plenty of aspen trees filling in the gaps. Aspen trees are pretty intolerant of the shade of other trees; they prefer complete sun. But whenever you see stands full of aspen trees in the BWCA, you can be pretty assured that they are clones of each other off of one massive root system below. In fact, one of the heaviest organisms on this planet, known as Pando, is a single clonal colony of aspen in Utah which covers over 100 acres. When larger trees like white pine start shading them out, or wind topples the larger aspen trunks above, the root system below is waiting to grow new trunks in whatever open patches of sunlight are available. Poplars are capable of spreading by seed also which does allow them to spread out beyond their root-system constraints. There are three species of poplar in the BWCA: Quaking Aspen, Big-Toothed Aspen, and Balsam Poplar. Quaking Aspen is the most common of the three in the BWCA. Look for their smooth, white bark the next time you’re in canoe country. It will not take you long to find them!
Balsam Fir: If poplar and jack pine are the signs of a forest rejuvenating itself, the balsam fir is the reset button. They are content to grow in the understory of bigger trees, but as soon as a big blowdown comes through and opens the canopy, the balsams take off. Balsam fir is a weedy tree which often grows in dense thickets of other fir after a big event like a blowdown. They are not a particularly hardy tree and have a bad habit of seemingly dying in a single year from droughts or pests such as the spruce budworm. Look for large swaths of dead forest after a bad drought year, and it’s a pretty good chance that balsam fir have something to do with it. When they die, balsam become the perfect fuel for hot, fast moving fires. As a smaller tree, balsam’s also act as ladders for fire to climb into the canopies of fire-resistant species like white and red pine. Balsam do not come back well after wildfires, so it may be a century or more after a fire before balsam really start filling in the understory again. When enough dead balsam clog the forest floor, the recipe is ready for another fire to come through and reset the forest. Look for dense stands of balsam anywhere the ’99 blowdown or the ’16 blowdown impacted the landscape.
White Pine: The queen of the eastern forest is less happy with the shallow soils of northern Minnesota than further south along the river valleys. That said, most people’s memories of the BWCA would be incomplete without it. The whine pine is fully capable of growing large and living a long life here, sometimes over three-hundred years if given the chance. It plays an important roll as a large, long-lived tree that’s beneficial to numerous species of wildlife including the bald eagle who prefers the white pine as a nesting tree. Seeing white pine here is usually indicative of a stand of trees which has escaped fire long enough for white pine to supersede the jack pine and aspen. To see truly ancient pines here, they have to either have avoided a fire for a long time or they have to have survived whichever fire has come through. White pine have thick enough bark to survive ground fires, but when smaller trees like balsam fir allow the fire to climb into the canopy, white pine lose their crowns and die. A great example of pines surviving a raging wildfire is found partway up the Gunflint Trail. No, I don’t mean the famous trees found right along the roadway, I mean a small stand just before Trail Center. Off the south side of the road are a collection of scraggly looking giant pines. To me, as a person familiar with trees, I can spot the tell-tale signs of their story from a mile away. Look at all the dead branches, look at the flattened tops indicative of trees who have not grown for a long while. Something is causing those trees to be unhealthy, and the reason stems back to a wildfire which burned through in the late 1800s and every old tree still bears scars from that event. When the fire was forced to jump the bog to the south, it likely landed on the ground and ignited a ground fire consuming brush and scarring the pines, before heading across what is now the Gunflint Trail. Because those trees survive, we have essentially a written record of a fire none of us were there to witness. Another great example sits along the popular Eagle Mountain trail. As discussed above, jack pine tell a history of fires across this landscape. The first part of the trail runs beneath an even-aged stand of jack pine descended from the 1929 Camp 3 Fire. As a person walks along, there is a single tree off the side of the trail that likely goes un-noticed by the average passerby since this gnarled white pine is actually shorter than the jack pine around it. Upon closer inspection though, this white pine has a massive scar from the 1929 fire which it survived. That scar weakened the tree which has struggled to survive and grow ever since. When wildfires go to the crowns of white pine though, it’s a different story. Near the portage from Winchell to Gaskin was a stand of trees Miron Heinselman had core-dated to germinating in the 1600s. For perspective, that means at the time of death, some of these trees were over 300 years of age. Then came 2006 and the Red Eye lake fire. The Red Eye fire was a small one as wildfires go, less than a mile wide when it crested the high ridge on Winchell. But as it jumped the lake, it scorched right through the ancient stand. A few of the twisted skeletons of these ancient pines can still be seen standing on the Gaskin side. As a lover of old-forests, it can be sad, but they also tell the story of this landscape and the important role that fire has in shaping and renewing this ecosystem.
Red Pine: Red pine thrive on the dry, shallow soil of ridge tops in the BWCA. Like white pine, they can grow back after fire, though likely not in the dense thickets like jack pine or poplar. They can naturally form mono-culture type stands if the conditions are right, with routine fires keeping the brush down. A healthy red-pine stand consistently managed by frequent ground-level fires is pretty special. Mature trees survive the fire which kills off less-tolerant species like balsam fir, clearing room for red pine seedlings to begin growing. For a young example of this, take the beautiful portage from Crab into Clark west of Burntside. A small control burn took off on a rampage north into the BWCA. It didn’t get too far, but did burn some acreage. Along the portage is a spectacular example of varying intensities of fire from total mortality of the red pine overstory, deep scarring on surviving trees, and some areas where the trees are just minorly charred. It’s a really cool example of fire working in a healthy way on a landscape. If it can avoid and survive fire long enough, red pine can live for close to 400 years in the right conditions such as the 1595 germinated red pine Heinselman found on Three-Mile Island (Seagull Lake.) Red pine also have a close connection with human history on the landscape. Certain pines on Saganaga, for instance, have scars from Native American axes peeling bark to harvest pitch from inside. Their survival carries on this fascinating piece of history. Other red pine were planted in rowed plantations after logging, something many people are familiar with. A close view of the air photos uncovers evidence of these stands still growing in the BWCA. Areas around the old Forest Center (Isabella Lake) show plenty of these “straight row formations” on the air photos, even still evident after Pagami Creek burned through. One can also see these stands west of Burntside in areas logged through the 60s and 70s. Whether growing as ancient, gnarled trees or as planted reminders of the past, look for the graceful crowns and pinkish bark of red pine the next time you visit the BWCA!
Paper Birch: Paper birch is another species often connected with blowdowns and fires. It is related to the yellow birch which sporadically is found in the BWCA, but is more common closer to Superior. Though related, they fill different ecological roles. The paper birch is closely connected to fire and the yellow birch thrives in old, rich stands with deeper soil. The thin bark of a paper birch can protect them from some rot, but anyone who has built a campfire around here knows it will not protect the tree from fire! The bark has a naturally occurring oil, which helps the bark to avoid decay, that makes it incredible flammable. Apart from fire, as long as the bark remains intact (such as no one pealing all the bark off the trees in a campsite) the tree remains intact. The wood in birch is pretty light though and as soon as the bark is gone, the tree begins to decay. They are not a long-lived species in any occasion, but they do have a secret weapon. Have you seen a cluster of birch growing close together somewhere in canoe country? They tell a story. Dead birch are capable of sprouting back from the stump if conditions are right. These sprouts often form around the perimeter of old stumps and, as they mature, form what we call a “fairy ring” or a circle of trees. With the old stump rotted away, the average person may never notice anything other than a closely clustered group of birch trees. Birch are also good at re-seeding after severe fires. Birch prefer mineral soil (the soil underneath the leaf-litter, rotting wood, and other organic material found at the surface.) This takes a very hot fire! If a fire is hot enough, and all the organic material burns away, it exposes the mineral soil which is perfect for sprouting lots of birch seedlings. In a grove of trees post-fire, look for the orange trunks of young birch to help distinguish them from the rapidly-growing, white-barked poplars nearby.
White Spruce: White spruce rarely dominate the landscape, but they are a long-lived large tree that can often be found growing alongside the pines in the centuries after the last wildfire. Their narrow crowns do not take up that much space, but they create a deep shade which can out-compete other trees below. They are capable of growing quite tall if given the opportunity. White spruce are an important food source for a wide-variety of wildlife including birds, squirrels, deer, and porcupine. Their thin bark is not fire resistant, so they don’t often survive fires. They can survive if growing in a sheltered spot such as by the lakeshore or in a valley so sometimes a young spruce can be seen peaking out a few feet above the re-generated jack pine, a sign that the young spruce survived the fire and had a head start on filling in the canopy. Spruce can be susceptible to a variety of diseases which can kill branches or the whole tree. Their dense canopies can also be susceptible to wind which topples trees with some ease in the BWCA where no deep soil is available for deep root systems.
Black Spruce: In canoe country, the black spruce is the king of the bog. In saturated, low-oxygen, acidic soils where all other trees barely scrape by or cannot survive, the black spruce reigns supreme. It can grow out of sphagnum mats floating on former lakes or in the forest alongside other trees. Because it is not the fastest growing tree, the bog is where it most often thrives where competition from other species is limited. The black spruce can often resemble a “doctor seuss tree” where the only living branches are found right at the tip-top. It also has a tendency for its branches to curve more than its white spruce kin, and can sport large plates of bark on its trunk. The black spruce can be a slow growing tree, but in the bog that doesn’t matter. Other trees aren’t competing for space and fires are less common in the rich, wet landscape. Some black spruces only ten or twenty feet tall can be a century old at times, just slowly living life in one of the harshest landscapes that canoe country has to offer.
Tamarack: The tamarack is another tree which loves to have its feet wet, though it isn’t quite as tolerant as the black spruce to full-time soaking. Though the tamarack is often found in the bogs alongside black spruce, it is also quite common along river banks in the BWCA. It has the distinction of having one of the largest native ranges of any tree in North America growing from Maine to Alaska. It is also special as Minnesota’s only native deciduous conifer meaning it has needles and cones like firs, spruces, and pines, but it sheds its needles every fall in a dazzling display of bright gold. Though tamarack can grow to some pretty large sizes and live a long while, it can be hampered by pests such as the larch sawfly and is pretty intolerant of drought. In the summer, look for a tree with the softest needles in the forest which have a distinctly blueish tint compared to the other conifers. A great place to see tamarack is along the Little Indian Sioux and Moose rivers in the western BWCA.
Northern White Cedar: If a jack pine’s strategy is to grow fast and respond quickly after fire, and a red pine’s strategy is to grow big and endure, the northern white cedar’s strategy is to outlast every other tree on the landscape. The northern white cedar is a long-lived tree if given the chance, reportedly 1000 years in some instances. They cannot grow as fast as a poplar or as tall as a pine, so how does the northern white cedar survive? On the landscape of canoe country, the northern white cedar has two growing strategies. First is to grow where no other tree wants to. The most common place to see cedars in the BWCA is along the shore growing along the water and often straight out of cracks in the bedrock. This is where they live the longest as sometimes wildfires miss the trees growing out on a rocky point. These trees often do not get very big as the limited space in bedrock cracks minimizes their nutrients and stunts their growth. They have another strategy, which is where we see them truly live up to their potential. Northern white cedar, being a shade-tolerant, long-lived tree, can simply wait out other trees in the understory. When the larger trees die, the healthy cedars take over the canopy. They create one of the deepest, densest shades of any tree in Minnesota, so dense that other trees struggle to grow beneath them. Once they have control of the overstory, their seedlings are one of the few species which happily grow in the dense shade, and the cedars can begin taking over a valley. That said, cedars are not fire tolerant. Their papery, oily bark is easily flammable. This is where their choice of growing conditions comes in handy again. A cedar’s favorite place to grow is in deep, shady river valleys. Some perfect examples in the BWCA are Eddy Falls, Johnson Falls, or the Hanson portage. In these deep, sheltered ravines, the trees get lots of nutrients, lots of water, and sometimes fires miss the steep valleys, jumping over them for dried-out forests on the other side. They can be susceptible to being uprooted by wind events, but another of a cedar’s adaptations comes in handy here. One of the northern white cedar’s other names is arborvitae, translated to tree of life, the name more commonly used in cultivation. It indicates the many medicinal uses for cedar and its role in the landscape, but I like to think it also represents its tenacity to cling to life whether from the seemingly barren cliff face or from the valley. When a cedar tips over, its life is not over. If just one or two major roots stay in the ground, a cedar will usually keep growing, turning its crown upwards against gravity. The massive trunk laying on the ground provides the perfect gathering spot for organic debris. When that debris breaks down into soil, young cedars have the opportunity to begin growing on top of the down log (which we now call a nursery log.) In this way, cedar stands can become a jumbled mess of different generations of cedars growing around, on top of, and underneath each other, creating one of the richest and most magical forest types in canoe country.
Red Maple: The red maple is never at its best this far north. For that, look for it in the rich river valleys of central Wisconsin! Here, it fills a niche as a never-common but often present component of the forest. The maples often seed in some decades after a fire as they are not fire resistant. They are usually good indicators of soil quality, with healthy trees growing from deeper, more organic soil and twisted, cracked, and stunted trees growing from shallower, mineral soil. Given the right conditions, the forest can be full of them, but that isn’t particularly common here. One stand I can think of sits near Saganaga between its shore and the shores of Lone Lake where a sizable tract of land is dominated by red maple. This is possible because it’s a large, flat valley with a creek winding through. The soil is not eroding quickly from the landscape and is tending to stay relatively moist, a good recipe for healthy maples. They can be unassuming in the summer because of their usual stunted nature, and shouldn’t be confused with the smaller moose maple which usually remains a shrub. The easiest time to see them is the fall when their flame-red hues pop out against the greens and yellows which fill the forest.
Black Ash: The stubborn, sturdy trunks of ash trees grow some of the heaviest timber in canoe country. They are pretty much constrained to deep, moist valleys where rich soil allows them to prosper. They grow incredibly slowly at times here, sometimes only a few inches a century. In the best of circumstances, they can grow into large trees fueled by available nutrients and plenty of water. A threat on the horizon, the emerald ash borer, has been working its way north since people seem to be incapable of not transporting infected firewood. Duluth is being hit hard, and places further south and east have been decimated by this invasive pest. It remains to be seen how quickly EAB will make it to canoe country, either by flight from Duluth or, more likely, a cabin-goers ignorance. However it arrives, it will have a detrimental impact on the future of ash trees in the BWCA. What remains to be seen is how the spread out nature of the stands and the future harshness of our winters impacts the invader. Look for marvelous ash trees near Johnson Falls, Cattyman Falls, or in the swamps along the Moose River.
Willows: Willows thrive in many of the same places as ashes and tamaracks. They love rich, moist soils. Most of the willows in canoe country stay as shrubs, though the diamond willow can occasionally last long enough to grow into a tree form and the occasional black willow can persist this far north. The diamond willow in particular has a lasting legacy as one of the preferred woods for crafts and some styles of furniture making. The willows of canoe country rarely grow large enough to dominate the landscape, and do not often form dense thickets here in the same way alder does. Look for isolated pockets of willow along streams and in marshy valley bottoms.
The Elms: The elms are another species from further south that do play a small role in the BWCA. Similarly to what is currently befalling the ashes, an introduced pest known as Dutch Elm Disease decimated elms in Minnesota through the 60s on, dramatically hampering the roll elms play in the lowlands. In the BWCA, elms are restricted to a handful of valleys where they continue to persist. Since elm have practically no adaptations against fire, they are pretty well confined to the valleys. Since elms do not root sucker, and are not high on the ridges for the wind to carry their seeds far-and-wide, in canoe country, their seeds are often moved by water or spread short distances by wind. Because of this, one can be pretty assured that anywhere one encounters elm in the BWCA, elm trees have existed for a reasonably long time. A couple places to see elm in the BWCA are the Long Portage (growing alongside ash, cedar, and yellow birch) and there are some very nice elm along the first stretch of the Sioux Hustler Trail.
The Oaks: Oaks are another group of species with a mixed history in the BWCA. On one hand, oaks do have a limited natural presence here, mainly on the top of dry ridges. I have often seen red oak growing this way and occasionally bur oak and pin oak. I have not personally encountered white oak in the BWCA, but I wouldn’t rule it out either. The oaks which do exist in canoe country are usually stunted, barely a large shrub, with lots of die back from overly intense winters without sufficient soil for them to stay healthy. Oaks are also closely tied to human history on the landscape. There are stories of the voyageurs planting oak trees as navigational tools since they easily stood out on the landscape. There is no documentation that I have found confirming specific sites, but the oaks on the Saganaga/Swamp portage would make a lot of sense in this role. There are also oak trees planted on old resort and cabin sites like some of the oak trees on Basswood or on Missionary. It’s hard to tell, specifically on Newton Lake and the Back Bay of Basswood, what is natural and what has persisted from historic planting. Regardless, the oaks through that stretch of Basswood are some of the healthiest I have seen anywhere in canoe country.