Getting Bogged Down

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Oh, my aching muscles...

Enjoy plants that thrive in marshy conditions

By ML Dehm
We are living in a time when our prized native wetlands are disappearing in spite our efforts to save them. The loss of the wetlands means a reduction in habitat for many native plants and animals. It is fortunate that the new awareness of water gardening and the availability of plants and materials now make it easy and affordable to keep your own bit of wetland habitat.
Commonly referred to as bog gardening, the creation of a place for moisture-loving plants is by no means new. Many ancient cultures maintained bog gardens.

In the Pacific Northwest, the importance of the wetland garden cannot be discounted. Native amphibians, the gardener’s friends, are finding their breeding grounds disappearing as the land is drained and new housing tracts are built.

Plants such as the native Skunk Cabbage (Lysichitum americanum) commands a premium price in Britain for its unique appearance — but is bulldozed here without consideration. Today’s home gardener now has the opportunity to be like their ancient counterpart and create a little oasis in a sea of construction.

Bog gardens are not as popular as the traditional pond, yet they are relatively simple to install and one can maintain many of the same plants as are kept in a pond setting. Unlike the structure of a pond — in which the goal is to maintain a constant water level — the bog merely requires a reduction of drainage.

While you certainly can go out and purchase expensive liners specifically made for water gardening, it is as effective and more affordable to use plastic sheeting. Used plastic sheeting and tarpaulins can be recycled in this way. Be sure they were not previously exposed to paint or chemicals which could hurt your plants. The bog liner also does not need to be padded or completely free of small holes or tears. Keep in mind however that the more holes and tears in the material, the more often you will need to water your soil.

Location is just as vital with the bog garden as it is with the pond. Many native wetland plants are shade tolerant, but some attractive choices are not. Browse your local nursery or water garden center before selecting your site and get a feel for the type of plants you prefer and discover their requirements.

As in pond construction, you will want to site your bog garden in a location where an overflow would cause no damage. If this is an impossibility you will need to build an overflow channel for possible runoff. Your bog will also be exuding more moisture into the surrounding ground than usual. Be sure that any nearby trees are tolerant of damp feet. Some trees that do well in damp soil are Coastal Redwood, Dawn Redwood, Maple, Birch, Willow and Spruce.

You can put the bog garden under overhanging foliage if desired, as the falling leaves will help to add needed nutrients and organic debris. Avoid planting under deciduous trees with excessive foliage drop such as the Big-leaf Maple. Raking a wetland can be a smelly business!

After choosing the site of your bog garden, outline the desired shape and excavate down 18 to 24 inches, saving the soil to one side. Put in your liner or plastic sheeting. Now you are ready to refill the hole.

There are conflicting opinions as to the type of amendment, if any, which need to be done to the soil before refilling your excavation. Some authorities suggest peat moss but others declare it too acid and recommend compost as an additive. If you have good quality garden soil it should be adequate for most bog plants without additives. Play it safe and make your final decision based on your local soil type and the requirements of the bog plants you’ve selected. Your nurseryman can help you here.

Return the soil, amended or otherwise, back into the lined hole until you’ve reached a few inches from the top. At this point it is good to start filling the bog with water, allowing soil and liner to fully settle. When the bog garden is fully soaked leaving a shiny film of water on top of the saturated soil, trim the excess liner leaving a lip of plastic up over the edge of the hole. Use the remaining soil to cover the exposed plastic and provide a slope down into the center of the bog.

It is time to plant—but in doing so, be very careful when digging not to cut through the liner with your trowel. You will also need a board to kneel on, laid out over the area you intend to plant. You have just made soil as mucky as quicksand.

Pacific Northwest natives for your bog are widely available at nurseries. Please don’t collect wild plants unless it is an area scheduled for draining and you have permission! Desirable native plants include the aforementioned Skunk Cabbage which is getting more recognition now due to its overseas popularity. Despite the name, this plant’s odor is only very strong if it is damaged.

Native sedges and rushes can add a lush appearance to the bog. Native bulrushes are too enthusiastic for a home garden but “mini” varieties provide for the same effect. The most popular flowers for a bog garden are one of the many species of iris.

Of the nonnative plants, the Gunnera manicata has spectacular enormous foliage. The pickerel rush (Pontederia cordata) is desirable for its long blooming season. You can even grow your own watercress — but be warned that this plant drinks a lot of water. You will need to water your bog frequently. Daring bamboo fans can select tall screen-like water bamboo. A special liner will be required to prevent the spread of its invasive roots. Bamboo liners can be obtained through bamboo specialists,
Bog garden upkeep is fairly simple. Excessive amounts of leaves need to be removed before they become sodden and decay. Weeds should be picked while small. Avoid disturbing the soil too much, as gases created by the anaerobic bacteria in the bog are likely to have an unpleasant smell. To prevent mosquitoes from breeding in your bog, look for a product that kills mosquito larvae without harming other insects or plants. It is in the form of a ring or pellet and is widely available in garden centers.

The most exciting part of having your own little wetland, is seeing the migration of wildlife to your yard. Birds are attracted to the damp ground, in search of insects and sips of water. You may find a fat, mottled, Pacific Giant Salamander under a rock or piece of wood (instead of slugs!) Possibly the best part of the bog garden is listening to the chirping of the tree frogs in the early evening and the contentment of knowing that you’re doing something to help the environment—and it looks great too!

NWGN archive published September 1998

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