Serving Northern St. Louis County, Minnesota

Deep Green

Marshall Helmberger
Posted 6/22/16

Cool, damp, dark, and oh, so green. That’s the quickest way I’d describe a visit to a mature black spruce bog. If you’ve walked through one of these before, you know exactly what I mean. …

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Deep Green

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Cool, damp, dark, and oh, so green. That’s the quickest way I’d describe a visit to a mature black spruce bog. If you’ve walked through one of these before, you know exactly what I mean.

The dense canopy of black spruce keeps the spongy surface of the bog in deep shade throughout the year. The ground, such as it is, lies buried beneath a thick layer of soft sphagnum moss that seems to absorb sound as much as water.

These are quiet places, where the silence is usually broken only by the high-pitched, jumbling call of a kinglet, or the staccato of a Cape May warbler. Other birds, like gray jays and spruce grouse, live here, as well, but the jays mostly skulk like silent ghosts and the grouse can usually be heard only when the males put on their elaborate breeding display in the spring.

Look down and you’ll see only a handful of different plants here in the bog, since relatively few can survive in the deep shade and the endless wetness. Pink ladyslippers grow here, sometimes in abundance. You’ll find bunchberry, a member of the dogwood family that seems to thrive in the deep shade. Indian pipe, a flowering plant without chlorophyll that derives its food from decaying vegetation much like a fungus, can often be found here as well. This is a plant that can survive in total darkness, so the dense shade of the spruce bog offers no challenge to its survival.

Labrador tea, Ledum groenlandicum, a member of the heath family, is probably the most abundant understory plant in spruce bogs. Its tough, leathery leaves are evergreen and when steeped in hot water, make a mild, earthy tea. Their showy white flower clusters, which appear in June, are now a bit past their prime for this season.

Spruce bogs are just one of several wetland types associated with northern peatlands, which are complex wetland systems common in cold parts of the world. Northern Minnesota is home to millions of acres of peatlands, far more than found in the rest of the Lower 48 states combined. They range from open fens, dominated by sedges, to the spruce bogs. Peatlands are constantly changing, it’s just that the change happens slowly, on a scale of hundreds of years, too slow for most humans to notice. The peatlands in Minnesota began as open water, ranging from ponds to virtual inland seas, like Lake Agassiz. Over time, they fill in with vegetation, and the vegetation eventually dominates to the point where the open water all but disappears and the vegetation begins to approximate a spongy version of “land.”

In the vegetation stew that lies underneath the surface of these disappearing lakes, oxygen is often depleted. Add cold temperatures and the natural acids that build up from the steeping of so much plant matter in water and the process of decomposition begins to break down. It’s why pickles will last nearly forever in the fridge.

Over time, the slowing of decomposition leads to the accumulation of peat, which is essentially un-decayed vegetation. Where the process of peat accumulation is still relatively young, peatlands tend to be wetter and vegetation is limited to things like sedges and low heaths. As peat begins to fill in, you’ll start to see a few stunted trees showing up, mostly black spruce or tamarack. As the process continues, the accumulation of peat becomes substantial enough that bigger trees can grow, and that’s when the black spruce start to take over in a northern Minnesota peatland. Once they do, they eventually form a dense forest and the plants that dominated when the peatland was more open soon disappear, leaving only the most shade tolerant of species growing under the canopy.

So much shade at ground level limits the growth of the understory, making the ground level surprisingly open. Thick sphagnum moss may carpet the ground, but because the peat in a spruce bog is relatively thick, the ground has a solid feel compared to other parts of the peatland and the walking is relatively easy. Here, the forest floor is still always wet, the morning mist can linger all day, and frogs lie in wait for the mosquitoes. And come mid-summer, the mushrooms can be amazing.

If you haven’t explored a spruce bog before… what are you waiting for?

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