Answer: Although many plants enjoy an evenly moist soil, many will not tolerate "wet feet" or saturated soil. There is also the question of how much light they receive, since many plants also have a preference for that as well.
You might consider some shrubs such as summersweet (Clethra alnifolia), Itea, deciduous winterberry holly (Ilex verticillata), and the shrub dogwoods with colorful twigs (such as Cornus racemosa or C. sericea) and possibly the evergreen Inkberry Holly (Ilex glabra) as these plants will tolerate wet feet and will also tolerate a wide range of light conditions.
Perennials to consider would include the Japanese iris (Iris ensata), cinnamon fern (Matteuccia pensylvanica)and ostrich fern (Osmunda cinnamomea) and Joe-Pye Weed. Astilbe, lily-of-the-valley, English ivy (Hedera helix), Cimicifuga, Ligularia, Monarda and asters are also plants to experiment with.
You might also look into creating a slightly bermed planting area to prevent the plants' crowns from being submerged or flooded in the spring. Sometimes an increase of just a few inches can make the difference in survival rates. Finally, you might also look into fine tuning the grading to divert some of the water, however this type of project probably would require on-site consultation with a landscape architect or similarly trained professional. I hope this gives you some ideas.
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