Home » Gardening Information » Garden Design
Chapter 3: Freshwater Wetlands of North America
If you have ever seen the vast marshlands of South Dakota's prairie potholes covered in a sea of ice, paddled through a foggy marsh at sunrise or listened to the throaty call of a bullfrog, you will no doubt agree that wetlands harbor a still serenity that makes them truly remarkable places—far different from their reputation as mosquito-ridden, malaria-infested, mucky, murky mires. This common misperception has led to their widespread demise. Until very recently, wetlands were drained or filled, farmed or paved over. Of the 215 million acres of wetlands that existed in the contiguous forty-eight states a couple of hundred years ago, only 99 million acres remain.
Despite their widespread devastation, you still can find freshwater wetlands in every region of this continent. Inland marshes, the most widely and evenly distributed, are characterized by predominantly herbaceous sun-loving plants and a few shrubs. They range from the sawgrass marshes of Florida's Everglades (the largest marsh complex in the United States) to the northern marshes of New England, home to great blue herons, moose and muskrats. The largest concentration of inland marshes is found in the prairie pothole region, extending from the north-central United States into south-central Canada. These vast grasslands are peppered with thousands of depressions formed 10,000 years ago, during the last Ice Age.
Glacial lakes, kettleholes and bogs are common in the northern states and Canada.
Peatlands—wetlands where organic matter decomposes more slowly than it is produced—occur most commonly in the northern U.S. and Canada. Peatlands include bogs, which often are blanketed with soft, spongy sphagnum mosses and receive moisture mainly through precipitation, and fens, seepage sites with an internal flow of groundwater, which are dominated by sedges and shrubs and commonly host wildflowers such as white lady slipper, shrubby cinquefoil and fringed gentian. The northern or boreal peatlands are most widespread in Canada and Alaska. In fact, Canada has the highest concentration of peatlands in the world, more than 600,000 square miles. These boreal wetlands also occur regularly throughout Minnesota and Maine, with smaller pockets in the Pacific Northwest, the western mountains and the Appalachian Mountains in West Virginia.
Swamps—wetlands with shady canopies of trees or shrubs—include the tupelo and Spanish moss-laden cypress swamps of the South; the floodplain swamps of the Mississippi Valley; the towering pine pocosins of the Southeast; the red maple swamps of the East; and the black spruce, tamarack and cedar swamps of the northern U.S. and Canada.