Soil that doesn’t drain properly can lead to major frustration along with struggling or dying plants. Re-grading the entire area is one option. Drainage can be improved by installing weeping tile, dumping quantities of sand and gravel, or building raised beds. These methods are not inexpensive in terms of materials or labour but a more practical solution would involve working with the condition and not against it. Many plants will tolerate dampness and thrive beautifully; just choose wisely.

Shade Trees

• If a large specimen tree is required, consider the London Plane Tree (Platanus acerifolia ‘Bloodgood’).
• Native trees like Hackberry (Celtis occidentalis), Pin Oak (Quercus palustris), or Red Maple (Acer rubrum) are particularly adaptable as they are used to fending for themselves in natural areas.
• Golden Weeping Willow (Salix Alba tristis) is certainly elegant and provides great winter interest with its bare yellow branches but it grows to an enormous size (15 m/48’ high and wide) and has roots that travel far beyond its crown. Plant it only if you have a very large property and it can be positioned well away from foundation walls, swimming pools, driveways, plantings and septic systems.

Evergreens

• Cedars (Thuja) grow very well in moist soil.
• Bareroot Hedging Cedars are often referred to as “swamp” cedars. Several upright or pyramidal forms are available growing anywhere from 3 m (10’) to 8 m (26’) tall depending on the cultivar.
• Emerald Cedar is probably the most popular with its vivid green colour in all seasons, and appealing texture.
• Globe Cedars fit in anywhere and can be pruned to maintain a tight, round shape.
• The Larch (Larix) and Dawn-Redwood (Metasequoia glyptostroboides) are two deciduous conifers that add great character to any garden. Both have soft foliage that turns golden-yellow in fall before the needles drop.
• Dwarf Bog-Rosemary (Andromeda polifolia) is a low, creeping broadleaf evergreen with blue grey leaves. It has small, pink, urn-shaped flowers in May. It also prefers acidic soil and can be planted at the base of the Evergreens described above.

Deciduous Shrubs

There are many shrubs that can grow in damp conditions.

• Native shrubs such as Arrowwood (Viburnum dentatum), Serviceberry (Amelanchier canadensis), American Elder (Sambucus canadensis), Red Osier Dogwood (Cornus sericea), Bayberry (Myrica pensylvanica), and St. John’s Wort (Hypericum kalmianum) are the most tolerant.
• If you want a tall shrub that will provide screening, consider Winterberry (Ilex verticillata), Bottlebrush Buckeye (Aesculus parviflora), Pussy willow (Salix caprea), European Highbush Cranberry (Viburnum opulus), or Brilliant Red Chokeberry (Aronia arbutifolius ‘Brilliantissima’).
•  If you want a shrub on a smaller scale, consider the old-fashioned Bridalwreath Spirea (Spiraea vanhouttei) which appears to grow just about anywhere including shade. • Summersweet (Clethra alnifolia) is very attractive in the summer garden and also attracts butterflies and hummingbirds.
• Hydrangeas provide interest with their white, pink, blue, or mauve flowers. They’re can be versatile in sun or shade but will droop without an adequate water supply.
• Dappled Willow (Salix integra ‘Hakuro-Nishiki’) is appealing spring through fall with narrow leaves that are green, white, and pink. It’s also available as a small standard tree.

Perennials for Sun, Partial Shade

Many perennials flourish in damp gardens. Consider any of the following:

• Gooseneck Loosestrife
• Great Blue Lobelia
• Cardinal Flower
• Sneezeweed
• Spiderwort
• Primrose
• Turtlehead
• Beebalm
• Aster
• Obedient Plant
• Goatsbeard
• Meadow Rue
• Globeflower
• Bergenia
• Bugbane
• Knotweed
• Daylily
• Siberian Iris
• Joe-Pyeweed

Perennials for Shade

• Virginia Bluebell
• Trillium,
• Foamflower
• Primrose
• Bleedingheart
• Astilbe
• Monkshood
• Ferns
• Toadlily 
• Ligularia
• Rodgersia

All of the above selections  withstand moisture and low light. Certain varieties of Hosta such as Frances Williams, Royal Standard, Krossa Regal, Lancifolia, and Sieboldiana ‘Elegans’ are appropriate considerations also.

Perennials for Bog Gardens

• These perennials can actually survive in shallow water and are often referred to as “marginals” or “bog plants”.
• Corkscrew Rush (Juncus effusus ‘Spiralis’) is very unusual with its bizarre coiled foliage.
• Make a large statement with Meadowsweet and Ornamental Rhubarb. These are tall and impressive.
• Blue Water Iris, Yellow Water Iris, and Japanese Iris flower beautifully.
• Marshmarigold is a spring treat with yellow, buttercup like blooms.
• Chameleon Plant and Ribbon grass are two perennials that spread rather quickly. To contain their lateral growth plant them in a deep, bottomless container.

For more suggestions on hardy perennials for wet sites, visit the Water Gardening section of a Sheridan Nurseries Garden
Centre near you.