A naturally occurring bog forms in a couple of different ways. Sphagnum moss may creep over the surface of a lake or pond and slowly fill it over hundreds of years. Or moss can smother a low-lying area of dry land, preventing surface moisture from evaporating. No matter which way a naturally occurring bog forms, the end result is a very specialized type of wetland characterized by an extremely inhospitable soil that's highly acidic and nutrient-poor [source: Environmental Protection Agency]. Since true bogs have to be watered with either distilled water or rain water, and because their finicky pH levels must be maintained within narrow margins, only the most dedicated gardener or conservationist would attempt to recreate a true bog in the garden. Therefore, the term "bog garden" refers more broadly to any marshy or soggy area whose soil is constantly moist, but never flooded [source: Burrell].
In a water garden, plants grow in standing water. Bog-adapted plants, however, do best with moist roots and dry crowns, leaves and flowers. Many bog plants are also sun-loving. A bog garden can require up to six hours of good sunlight to really thrive [source: Fisher]. And while the proliferation of bogs in places like Ireland and Finland may lead people to think of them as cold, damp places, bog gardens can also thrive in hot, humid climates. On the other hand, people in dry, arid climates might prefer to try their hands at bog gardening in containers, since the effort and expense of maintaining the water level in a larger bog garden will likely outweigh the pleasures of creating one.
Bog gardens work best when they're developed with a plan in mind. Tossing some moisture-loving bulbs into a soggy area of your yard does not constitute a proper bog garden. Some of the most gorgeous bog gardens are created in order to give an adjacent pond soft, natural looking edges that blend into the landscape. Other bogs exist as opportunities for adventurous botanists to cultivate rare, exotic and even carnivorous plants. Still other bog gardens serve a practical purpose by turning a soggy, problematic area of a yard into a fascinating and functional habitat.
Once you've selected an approach, it's time to grab a shovel and start digging. See the next section to see how excavating a bog garden works.