It's easy to recognize potential bog garden sites. Since water runs downhill, look for boggy areas at the base of hills and in natural depressions. These will be the places where the yard never quite dries out and the soil ranges from a bit squishy to downright soggy. The topsoil might appear dry at times, but the root zone should always be moist.
Unlike a rain garden, which is designed to handle brief inundations after a downpour but then drain to nearly dry, a bog garden is best suited to a water-retentive site that will always (or nearly always) be wet. Standing water is not necessary, but many bog plants will not thrive unless their roots have access to near-constant moisture. Set bog plants directly into the ground. Or plant into sunken terra-cotta pots, which allow moisture to reach the roots but keep aggressive spreaders in check and make it easier to relocate tender perennials to warmer winter quarters.
Try several of the plants described here—or experiment with other bog-loving plants, often sold as marginal plants for water gardens—and watch as a once-avoided area of muck and mud becomes a garden to admire and enjoy.
Start with Structure
Every landscape needs vertical structure, whether tall and towering or short and spikey. Plants in the Cyperus genus offer excellent structure for boggy areas. Umbrella palm (C. alternifolius) stands 4 to 6 feet tall and carries an "umbrella" of narrow leaves that can reach 2 feet in diameter. Papyrus (C. papyrus) stands even taller–5 to 12 feet-while dwarf papyrus (C. isocladus) barely exceeds 12 inches. Most Cyperus species are tropical perennials and will overwinter in USDA Plant Hardiness Zones 8 to 11, but umbrella palm tolerates Zone 7. In colder climates, bring plants indoors in winter.
Foliage plants offer a fine contrast for other garden plants. Constant favorites for bog and pond gardens are the various elephant ears (Colocasia esculenta), which range in color from deep green to near-black. 'Mojito', for example, combines dark purple freckles and flecks on rich medium green leaves. Other favorites include deep purple 'Black Magic' and the unusual 'Coffee Cups', which forms 6-foot-tall clumps of deeply cupped olive green leaves. All do best in the shade, and most will overwinter in Zones 7 to 11. In colder climates, bring the plants indoors for the winter, or mulch heavily. When purchasing, look for large, fresh bulbs, as these will reliably produce the best foliage.
Accent with Flowers
North American bog gardeners are lucky to have numerous hardy and attractive natives to choose from. Deep red cardinal flower (Lobelia cardinalis), for example, is nearly indestructible (and quite rampageous). It is a hardy perennial (Zones 2 to 8) that thrives in sun to shade and blooms from late summer through fall. Swamp milkweed (Asclepias incarnata)–hardy in Zones 3 to 9–has summer-blooming pink flowers that hummingbirds and butterflies can't resist.
Finish with Groundcovers
Low-growing plants prevent erosion, hide mud, and preserve soil moisture for other bog plants. Many groundcovers also produce masses of flowers. Moneywort (Bacopa mon-nieri) spreads across boggy soil and shallow water, and is almost constantly covered in white flowers with pink and blue accents. Native moneywort handles light foot traffic and thrives in sun or shade. Hardy in Zones 6 to 10.