Other than plants intended for the pond, marginalised or oxygenating – species like to dip into moisture but not to sit in it. Lily of the valley, Daylilllies and Hibiscus can all tolerate more than enough moisture.
It is worth understanding then why the area is wet or over saturated. An ill drained area can be altered to improve water runaway so that the area is moist but drains. If the soil is compact this might be the reason for the accumulation of water. It might an option to install land drains or conversely change the consistency of the soil to allow water to penetrate.
Cornus do well in moist areas and provide effective winter colour. Dogwood produces attractive foliage with white flowers so has a purpose all year around. Very easy to keep and most aspects are adapted to. Easy to prune, a couple of inches from base and it comes back up in Spring.
Spring flowering Kalmia do well in these conditions with a good degree of light. As long as the sun is shining on the species, the plant can sit in moisture. It can tolerate partial shade as long as the soil has some drainage and on the acidic side which is why it goes well with Camellia’s and Rhodendrons. Little pruning is necessary but have a tendency to become leggy. A clip to keep its shape but is slow to grow out of control.
Some Salix alpine varieties will cope with some saturation as will Betula pendula, the silver birch, although some drainage is still needed. Hydrangeas are probably one of a few plants that devour H20. However, Hydrangeas cannot sit in it either as to do so would kill them rather quickly. They prefer cool, moist and shaded spots. A smaller water lover is a certain grass, Carex. This is usually in planting combinations with other ornamental grasses so often doesn’t lend itself to a pond location.
There are smaller species like Hostas (a rich and acidic soil for these plants) and Ferns (generally anywhere) that sit well in moist areas but again a crown rot issue can arise if proper care not taken of them. A grass that goes well with Hostas is Hakonechloa macra, it doesn’t mind moist soil but it must be well drained. Monarda – well drained, Rudbeckia – well drained. The problem of moist not wet still resides. Liriope too is resilient of tough conditions and can cope with full shade but not over saturated soil. It still needs to be well drained.
Nothing would be better than probably addressing the problem unless you want to create an actual bog or marsh area for Bull rushes, Gunnera, Irises and alike and even here there needs to be a degree of drainage. Not too much seems to survive in a pool of water.