Bog gardening makes use of previously unsuitable landscape areas. Places with seep springs, a high water table or a low spot with poor drainage can be made attractive with a wide variety of plants adapted to these conditions. Bog gardens can also be constructed as an adjunct to a pond or to grow rare and unusual species of moisture-loving plants that will not thrive elsewhere in the garden. Plants for the bog garden have unique foliage shapes, striking coloration and are easy to care for.
Acorus calamus "Variegata" (Variegated Sweet Flag) has iris-like foliage banded in pale yellow and dark green. It looks particularly striking mixed with plants that have purple foliage, such as some types of canna. "Variegata" will grow in sun or part shade. Reaching 3 feet tall, this plant will spread gradually to form a large clump. Hardy to growing zone 3.
Acorus gramineus (Japanese Sweet Flag) has grass-like foliage that is vibrant yellow in color. It stands out well in shaded areas and planted against a darker colored background. Acorus gramineus is much smaller than other calamus varieties, slowly growing into a clump a foot wide and tall. It is slightly less hardy than "Variegata," surviving to zone 6.
Cannas thrive in very rich, wet soil. They should be given their own space in the bog garden, not only due to their large eventual size, but their high nitrogen requirements as well. Soil should be composted chicken or steer manure mixed with peat moss to hold moisture. As much as they love summer water, winter wetness will kill them. In zones 7 and south, cannas may be left in the ground over winter. In northern zones, dig them up in the fall and store in a cool place that never gets below freezing.
Of all the bog garden plants, cannas have the most widely varied foliage and flower color. Varieties such as "Australia" have leaves that are deep purple with black tones. "Pretoria" and "Stuttgart" display variegated foliage. For a truly shocking effect, plant "Phaison," with its loud striped leaf colors of purple, orange and red.
Gunnera manicata (Giant Rhubarb) will attain huge proportions in the bog garden. Rough textured leaves will grow 4 feet in diameter, with the mature height and spread of the plant reaching 10 feet or more. This is a good selection for damp, partially shaded areas of the garden where nothing else wants to grow. High summer temperatures can cause wilting and leaf loss if adequate moisture cannot be maintained. Winter cold tolerance can be increased by heavily mulching the crown of the plant. Hardy in zones 6 through 9. Survival in zone 5 is possible with deep mulch and a plastic covering to prevent moisture reaching the crown of the plant and freezing. Cover the plastic with a few layers of burlap to further insulate the plant and prevent the plastic from overheating.
Petasites japonicus "Nishiki Buki" (Japanese Coltsfoot) has round leaves up to 2 feet wide, liberally splashed with shades of yellow and cream. Although petasites can be invasive in some areas, it can be easily controlled by withholding water or planting in a submerged tub. Soil should be fertile but this plant will even tolerate clay. This variety will grow in either full or partial shade. Flowers emerge in a fragrant white cluster in early spring. Hardy in zones 5 through 9.
Sarracenia purpurea (Purple Pitcher Plant) is an odd looking but attractive addition to the bog garden. Short, bulbous purple pitchers appear in early spring, radiating outward from a central clump. Sarracenias will not do well in very rich or high nitrogen soil. They do best in a mixture of peat moss and sand. This means they will have to be planted in an area separate from other bog plants with different soil requirements. Sarracenia purpurea will grow in partial shade, and is extremely hardy, surviving temperatures down to -15 F. Pitcher plants are carnivorous, attracting insects which crawl into the tubular body of the plant and cannot escape. Feeding insects to the plant is not recommended.