How Bog Gardens Work


Creating a bog in your yard is hard work, but with a little dedication you can maintain one that looks natural.
Creating a bog in your yard is hard work, but with a little dedication you can maintain one that looks natural.
Matt Cardy/Getty Images

In the air is the hum and buzz of mayflies and midges, followed by a heron's sudden rush to flight. It's sunnier than you'd think, here in the bog. Water peeks through clumps of evergreen shrubs. A startling red salamander darts across a bed of moss. A carnivorous pitcher plant snaps shut on an unsuspecting fly.

Bogs and other types of inland wetlands appeal to a lot of different people. The gothic among us, dark romantics and fans of the epic legend "Beowulf," are drawn to creepy stories of bodies with skin and internal organs still intact, preserved for centuries in the acidic soil of bogs [source: Tyson]. Mystics and the spiritually inclined are attracted to the elemental nature of bogs. The way they purify and preserve and sometimes even burn can fascinate. Conservationists and environmental activists probably count themselves as the biggest fans of bogs and other types of wetlands.

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A bog's fragile and interconnected ecosystem performs a multitude of essential and too often overlooked functions. Bogs are vital in controlling flooding, for instance. Countless animal populations rely on them as a habitat for themselves or for other populations upon whom they're dependent. And finally, wetlands are home to many rare and exotic plant species, including the carnivorous sundew and the northern pitcher plant [source: Environmental Protection Agency].

A natural bog can take hundreds -- sometimes thousands -- of years to form. A committed gardener, on the other hand, can create a truly stunning bog garden with only a month or so of careful planning and hard work. Take a look at the next section to see how a little slice of the bog might work in your own backyard.

A Bog in the Garden?

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.

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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.

Dig In: Excavating and Choosing a Pond Liner

Bog gardens work best in sunny, low-lying spots. A difficult, soggy area in your yard where water collects is ready-made for bog gardening. The bottom of a slope or an area near your house where the bog could catch runoff from the roof would also work well. Bogs are often cultivated along one or more sides of a pond to create soft edges that transition naturally into the landscape. You wouldn't want to put a bog on a hillside or in full shade.

Bog gardens require quite a bit of work at the outset. The first step is to dig out a trench with a flat bottom and slightly sloping sides, setting aside the excavated soil on a tarp. The bigger and deeper the hole, the less maintenance the bog garden will require -- at least in terms of watering. A depth of 18 to 30 inches (45.7 to 76.2 centimeters) ought to do the trick [source: Burrell]. If you happen to have a pond, give it soft, natural looking edges by connecting either an independent or an attached bog garden [source: Fisher].

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  • To make an independent bog garden, leave a dam of hard-packed soil higher than water level along one edge between the bog and the pond. This prevents water in the pond from seeping into the bog and vice versa.
  • Create an attached bog garden that waters itself by taking moisture from a pond. Leave a hard-packed dam a little lower than the pond's water level, and top it with a semi-permeable substance such as sod or stone.

By far the cheapest and easiest way to line a bog garden is with an artificial membrane. Just calculate the size you need, lay it evenly inside the trench and hide the edges under rocks or cascading ground cover. You could also use a hard shell liner or even a plastic pool. If you hit clay during the excavation process and don't mind a lot of extra work, you can remove some of it and use it to create a watertight basin for your bog garden. Mix the clay with a little water until it is malleable, and then smooth it over the bottom and sides of your trench, using a rammer or a heavy tamping tool to pack it down [source: Perry]. You could also use concrete to line your bog garden; however, if you go this route, consult with your local garden center, since some sources suggest blending the cement mixture with other substances such as sand or washed shingles.

Now that you've seen what sort of vessel it takes to house an in-ground bog garden, let's fill it with soil and talk about how to keep it watered.

Drainage, Water and Soil for Bog Gardens

Many gardeners use several varieties of moss for their bogs.
Many gardeners use several varieties of moss for their bogs.
Chris Hepburn/Getty Images

The bottom of a bog should be watertight. However, the top foot of a bog requires a bit of drainage. Simply poke or drill small holes through the liner at regular intervals along all sides of the top 12 inches (30.5 centimeters) of the trench. This will keep a bog's topsoil relatively dry and ensure that the crowns of plants don't freeze or rot [source: Burrell].

Because a bog needs to stay evenly moist at all times, it's important to integrate a method of watering into the bog design. Here are three simple ways to keep a bog garden moist:

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  • Install perforated PVC piping at each corner of your trench, leaving a couple of inches sticking up above the surface. Place your hose, rain barrel siphon or other water source into the above-ground end. Plug the buried end of the pipe, and water will seep out slowly and evenly from the perforations.
  • If you need an even more subtle watering method, place a smaller perforated pipe inside a larger one and fill the space between with gravel. This reduces flow to a bare trickle. Remember to plug the buried end.
  • Run rigid perforated piping horizontally along the bottom of the trench and connect it with an elbow to one of the two types of vertical perforated piping as described above. Cover the horizontal pipe with gravel to keep the drainage holes from becoming clogged with soil, and make sure to plug the buried end [source: Burrell].

Many true bog plants are adapted to thrive in poor, nutrient-deprived soil; standard compost is generally too rich for them. If you want to cultivate bog-adapted plants, most sources suggest filling the bog with a mixture of peat moss and sand [source: Fisher]. However, a wide array of non-specialized bulbs, perennials and shrubs can also thrive in constantly moist conditions. If these are the plants you want to grow, fill your bog garden with a mixture of 50 percent excavated soil and 50 percent compost [source: Burrell].

The type of soil you choose will depend on the kinds of plants your bog will support. In the next section, we'll explore different kinds of plants that work well in bog gardens.

Bog Plants: From Flowering to Flesh-eating

Sphagnum moss is one of the most common plants found in bog gardens.
Sphagnum moss is one of the most common plants found in bog gardens.
Kathy Collins/Getty Images

Here are a few of the more popular plants that thrive in bogs:

Sun-loving bog perennials

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  • Day Lily: Hemerocallis, or day lilies, are the stalwarts of bog gardening. Their height depends on the species, and they bloom from May to September in a multitude of colors.
  • Heather: Erica, or heather, is a tailor-made ground cover for bogs. E. tetralix, or "bog heather," produces pink flowers all summer long [source: Perry].

Shade-tolerant bog perennials

  • Monkshood/Wolf's bane: Aconitum. These blue-purple flowering plants are hardy in a variety of temperatures. They bloom in summer, and grow 3 to 5 feet (.9144 - 1.524 meters) tall and their roots are poisonous.
  • Yellow Waxbells: Kirengeshoma. This showy plant flowers in early autumn, after many other bog plants have shed their colors. Its bright yellow cone-shaped flowers adorn deep purple stalks and grow 2 to 4 feet (.6096 - 1.2192 meters) tall [source: Perry].

Carnivorous and specialized bog plants

Unscrupulous plant vendors sometimes gather these species from the wild, damaging their fragile habitat. Make sure to verify that your carnivorous and specialized bog plants were propagated in a nursery.

  • Pitcher Plants: Sarracenia. These insectivores feature clumps of upward-turning trumpets that collect rainwater and send insects to their watery deaths. The "Ladies in Waiting" and "Dixie Lace" hybrids were developed especially for home gardeners and will grow to zone 5 with some protection in the winter [source: Fisher].
  • Venus Flytrap: Dionaea muscipula. The shell-shaped leaves of this famous carnivore are tipped with spikes and snap shut to trap unsuspecting insects. Venus Flytraps grow to 18 inches (45.7 centimeters) tall and are a must-have for carnivorous plant collectors [source: Fisher].
  • Sphagnum Moss: This is the foundation for any true bog garden. Fill your bog with water and let a layer of living moss float on top. As the mat grows and decays, it will deposit peat into your bog. Over time, the moss will become thick enough to support plants, shrubs and even trees [source: Burrell].

Other bog plants

A huge variety of plants, bulbs, grasses, trees and shrubs have adapted to grow in moist conditions. Bog maple, bog cypress, bog rosemary and varieties of lily, daffodil and narcissus are but a few of the many other bog plants worth exploring.

Now that your bog is planted, check out the next section for information about maintenance and creating container bog gardens.

Bog Garden Maintenance and Container Bog Gardens

The type of maintenance your bog garden requires will be heavily dependent on the sort of bog garden you have. A non-specialized bog is fairly simple to maintain. If you have created specialized bog garden, however, the maintenance is a bit more involved.

Once a non-specialized bog garden is established, it's not all that difficult to maintain. The very conditions that make bog gardens inhospitable to non-adapted plants also make the habitat undesirable for many of the weeds that plague "regular" gardens [source: Burrell]. Give your bog garden the once-over every so often and pluck any weed and tree seedlings before they get established. If freezing is a concern, consult with local professionals about how to winterize your bog garden. Watering is the biggest concern with bog maintenance, so make sure you have a watering plan in place.

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A natural bog forms when sphagnum moss decays, slowly choking a low-lying, soggy area with acidic peat. These are the conditions you'll have to duplicate to create specialized bog garden at home. Because a specialized bog must be watered with distilled or rainwater, be sure to implement a watering design. The depth should be no more than 2 feet (.6096 meters), and it should be filled with a mixture of sand and peat moss. Ideally, you would and top a specialized bog with a layer of living sphagnum moss, which can be difficult to come by. Consult your local garden center for help.

Let your specialized bog settle for at least a month before planting. Failure to do so may damage new plants. You'll also want to wash the roots of your plants before you to install them. Once plants are in, you will begin an ongoing game of cat and mouse with your bog's pH. It must stay highly acidic in order for plants to thrive [source: Burrell].

Bogs are the perfect habitat for egg-laying insects. Some of these, such as butterflies, may be desirable. Others, such as mosquitoes, are a terrible nuisance. Fish in an adjacent pond may help to keep insect populations down. Insectivorous plants will also help rid the garden of pests. Mosquito dunks made with a microbial larvicide like Bacillus thuringiensis israelensis, a bacterium that occurs naturally in soil, are safe and work for up to thirty days [source: Environmental Protection Agency].

Still have questions about how bog gardens work? We answer a few of them in the next section.

Bog Gardens: Things to Consider

Above is an example of a natural bog, located in Jura, France.
Above is an example of a natural bog, located in Jura, France.
Jean-Pierre Pieuchot/Getty Images

Here are just a few of the things you might want to consider before you undertake building a bog garden.

  • Cost -- The biggest cost factor will be the bog's size. Material and plant costs vary, so check with your local hardware store or gardening center to determine the cost of building your bog. Some general materials you'll need in order to get organized are a pond liner, perforated PVC piping, a growth medium and bog plants.
  • Time -- Ideally, plan for a month when building a bog garden. Digging the trench will be time consuming. Sources recommend filling it with soil and then flooding it, letting it settle for about a month to achieve a stable and ideal pH before installing plants. Of course, impatient gardeners can push up the timeline somewhat; however, if the aim is to create a specialized, true bog, it's especially important to wait about a month before planting [source: Burrell].
  • Climate and Weather: Technically, some form of a bog garden could be created and maintained in any climate. However, the constant watering that would be required would be extremely costly, time-consuming and ill-advised in an arid environment. Desert gardeners are advised to make due with a container bog.Weather is also a consideration. Drought is absolutely lethal to a bog garden, but flooding can be a concern, too. It's important to ensure adequate drainage by puncturing holes through the liner in the top 12 inches (30.5 centimenters) of the bog [source: Burrell].Also, true bogs are filled with peat, which can catch fire and burn. If your bog is a true, specialized bog then you should be mindful of when lightening strikes [source: Environmental Protection Agency].

Bogs are one of nature's wonders and they make a great addition to any garden. So grab a shovel, let loose a chorus of "The Rattlin' Bog Song" or another of the many bog-related Irish folk tunes, and dig in.

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Sources

  • Burrell, C. Colston. "The Natural Water Garden." Brooklyn Botanic Garden, Inc. 1997.http://www.bbg.org/gar2/topics/design/handbooks/watergarden/8.html
  • Environmental Protection Agency. "Bogs." Posted dated not published. (10.12.09)http://www.epa.gov/owow/wetlands/types/bog.html
  • Environmental Protection Agency. "Impacts on Quality of Inland Wetlands of the United States." Posted dated not published. (10.12.09)http://www.epa.gov/owow/wetlands/wqual/miv.html
  • Environmental Protection Agency. "Larvicides for Mosquito Control." 04/11/07. (10.12.09)http://www.epa.gov/pesticides/health/mosquitoes/larvicides4mosquitoes.htm
  • Fisher, Kathleen. "Complete Guide to Water Gardens." Creative Homeowner. 2000.
  • Perry, Frances. "The Water Garden." Van Nostrand Rheinhold. 1981.
  • Tyson, Peter. "America's Bog People." Posted date not published. (10.12.09)http://www.pbs.org/wgbh/nova/bog/america.html