By Gaston Tessier
If your yard has a chronically wet or damp area that you have always considered a curse, don't despair. Poor drainage may be a result of heavy clay soil or a local water table that is too high. However, you can easily turn these drawbacks into assets. By growing plants that thrive in moist places you can transform these problem sites into beautiful bog gardens. This will also provide wonderful habitat for wildlife.
The ideal location would be an area with a bit of shade at the edge of a woodland. However, it would also work in a sunnier site as long as you make sure that it doesn't completely dry up during periods of drought.
If the area is open and bare, you may want to start with trees or shrubs that tolerate boggy soil. This would add structure, provide a natural look, and create a perfect microclimate for moisture-loving plants. Perennials can then be added on the south side of any trees or shrubs so they receive plenty of light. Most plants that grow at the edge of a natural pond will do well in bog gardens.
Bog gardens are among the easiest water features to install and maintain. They are simply beds of moisture-retentive soil spread over a pond liner, which helps the soil retain water. The chosen site should receive at least six hours of direct sunlight per day. To create your bog garden:
- Begin by digging a hole of the desired shape and size to a depth of 6 to 18 inches.
- Spread an inexpensive polyethylene liner over the hole.
- Pierce the liner every three feet or so with a garden fork. (If you find later that the drainage is too slow, you can add additional holes using a pointed stake and mallet.)
- Spread 2-3 inches of pea gravel on top of the liner. The gravel allows the excess moisture to drain from the soil when it is too saturated. (Bog plants need moisture, but they also need some drainage.)
- Trim the plastic so that the edges will be concealed under the soil surface.
- Fill the hole with a high quality, moisture-retentive topsoil mixed with an equal amount of compost. You can also mix in sphagnum peat moss, but use it sparingly.
- Plant moisture-loving species in your new bog and water well.
- Fertilize occasionally using compost - slow-release fertilizers break down too quickly in moist conditions.
- The soil should be kept almost soggy.
- Perennials that thrive in moist conditions tend to multiply rapidly, so they may need to be divided after a few years.
If you wish to create a bog in a very dry area, it might be worth considering an irrigation system before you add the soil. The simplest system is a short length of soaker hose running along the bottom and then to the top of the eventual soil surface. A quick-release hose coupler will allow you to periodically connect it to a garden hose to allow water to seep slowly and evenly into the soil.
A wide variety of plants that thrive in shallow water will also do well in a bog setting. Some suggested plants are: yellow flag (Iris pseudacorus), marsh marigold (Caltha palustris), Siberian iris (Iris sibirica), astilbe (Astilbe spp.), Joe-Pye weed (Eupatorium purpureum), cardinal flower (Lobelia cardinalis), bee-balm (Monarda didyma), goatsbeard (Aruncus dioicus), globeflower (Trollius spp.), and turtlehead (Chelone glabra).
Ferns, aquatic grasses, cattail and other aquatic plants of your choice may be added if space permits. You will have to experiment to see which plants work best in your regional climate. If the roots of your plants show signs of rotting, add more topsoil mixed with vermiculite. The original mixture may have been too rich.