If your soil doesn’t meet the well-drained requirement specified for many perennials, don’t allow that to bog down your gardening plans. According to Clemson Cooperative Extension, there are quite a number of plants which don’t mind being all wet!
Perennials for Very Moist Soil
Which perennials you choose will depend on the level of moisture in your soil. If it can be downright mucky at times, look for plants that have “swamp” or “marsh” in their common names -- or their cultivars.
- Swamp milkweed (Asclepias incarnata, U.S. Department of Agriculture hardiness zones 3 through 9) feeds both monarch butterfly larvae and your senses with fragrant pink summertime blossoms atop 2- to 4-foot stalks. Cultivars include the deeper pink 'Soulmate' and white 'Ice Ballet.'
Marsh marigold (Caltha palustris, USDA zones 2 through 9) lights up the spring with shiny heart-shaped leaves and sunny yellow flowers on plants under 1 foot tall. For even more showy blooms, try the double ‘Plena.’
- Swamp rose (Rosa palustris, USDA zones 3 through 8), one of the few roses that doesn't mind getting its feet wet, seldom exceeds 4 feet in height and has 2-inch pink blooms in early summer. The cultivar ‘Scandens,” found in USDA zones 5 through 8, lacks the thorns of the original.
- Swamp sunflower (Helianthus angustifolius, USDA zones 5 through 9), illuminates autumn with 2- to 3-inch golden blooms on 5- to 6-foot maroon stems. For a less leggy look, try the shorter ‘First Light’ or ‘Gold Lace.’
- Swamp rose mallow (Hibiscus moscheutos, zones 4 through 9) happily soaks up excess water to maintain its mammoth, late summer and early autumn, 10- to 12-inch dinner-plate-size pink flowers on 4- to 6-foot plants. Cultivars include the dark-centered pink and white "plates"
of ‘Southern Belle’ and ‘Luna Pink Swirl' -- the latter hardy in USDA zones 5 through 9.
Other splashy plants that don’t mind sogginess, and that are often planted on the edge of water gardens, include the Japanese iris (Iris ensata, USDA zones 4 through 10) and the white arum lily (Zantedeschia aethiopica, USDA zones 8 through 11).
Perennials for Moderately Moist Soil:
If your soil is more evenly moist than mushy, the following perennials should flourish for you. With the exception of the sun-loving aster, you can place these species in partial shade -- full shade for the astilbe -- to help preserve their soil's dampness.
- New England aster (Aster novae-angliae, USDA zones 3 through 8) grows from 4 to 6 feet with narrow-petaled late summer and autumn flowers. Cultivars include the pink ‘Alma Potschke’ and lavender ‘Hella Lacy.’
- Astilbe (Astilbe x arendsii, USDA zones 3 through 9) hybrids generally stand 1 1/2 to 4 feet tall with lacy plumes of blooms in early to mid-summer. Cultivars include the pink ‘Bressingham Beauty’ and white ‘Diamond.’
- Lily of the valley (Convallaria majalis, USDA zones 3 through 9), one of the smallest water lovers, seldom surpasses 1 foot in height with pointy upright leaves and spikes of diminutive white bell-shaped blooms in spring. A colorful variation, var. rosea, offers pink flowers instead.
- Joe Pye weed (Eupatorium spp., USDA zones varying from 4 through 11) can tower 6 to 8 feet tall in the wild with large heads of pinkish-purple flowers in summer through autumn. Fortunately, you can have a similarly lush look with "toddler" cultivars such as dubium ‘Little Joe’ or ‘Baby Joe’ -- both hardy in USDA zones 4 through 9 -- which shouldn’t grow much taller than 3 feet.
- Hydrangea (Hydrangea spp., USDA zones varying from 5 through 10) boasts large leaves and mopheads or lacecaps of flowers, which make it a thirsty plant that is less likely to wilt when planted in soil which doesn't dry out. Shrubby types can grow to 15 feet and climbing types, to 50 feet.