If you live in the Pacific Northwest and you have an especially soggy area that you'd like to address, you can plant specific things that like "wet feet!" (At least that's the term the nursery uses for plants that can tolerate (or even enjoy) being planted with lots of surrounding water." If you have listened to my podcast, you know that I love to plant things that attract butterflies, bees, hummingbirds and other wildlife when possible!
Assessment
Let's first think about how wet the area is. The key to making your planting combination work begins with understanding your site, its unique characteristics, and the seasonal conditions.
A "soggy" area would be consistently wet and spongy with high water saturation. The soil is damp underfoot, but never swampy.
Moderately wet locations have soil that is consistently moist but not soggy year-round (read into this, it probably is not a full-sun location.)
Areas that become saturated with standing water during the rainy season but dry out between rainfalls are considered intermittently or seasonally wet. This type of area may also be dry for several months once the rainy season is over.
Seasonally wet sites
Tree: river birch (Betula nigra) I'm a fan of this choice because it also tolerates the increasingly hotter temperatures we are experiencing with global warming. Bonus that it's disease-resistant. It prefers moist, acidic, fertile soils including semi-aquatic conditions, but also tolerates drier soils. Consider using bark mulch to keep the root zone cool and moist.
Shrubs: 1. pussyswillow (Salix discolor) will give your site interest at the tail end of winter when not a lot of other things are doing much yet. 2. Red twig dogwood (Cornus sericea): Deciduous multi-stemmed shrub to 16 feet tall that I actually have in our yard! It has wide, reddish bark that adds to winter interest. Birds love to land in and find protection in this tall treelike shrub. It has flat-topped clusters of white flowers followed by white or bluish berries. It does well in sun/part-sun; butterfly host. 3. Ninebark (Physocarpus capitatus): This is another one I have in my own yard! Multi-stemmed deciduous shrub grows to 8 feet or more. It's leaves resemble maple leaves and birds love this one as well. It has clusters of white flowers in late spring; older stems have shredding bark but birds take this to use for nesting. It likes sun/part shade; butterfly host.
Perennial: butterfly weed (Asclepias tuberosa) this bushy, 1 1/2-2 ft. perennial is attractive because of its large, flat-topped clusters of bright-orange flowers and as you might have guessed, attracts butterflies. Bloom Time: May , Jun , Jul , Aug , Sep
Soggy year around
Larger textural grass: rush (Juncus spp) This is a hardy choice and is found in a lot of drainage ditches throughout Portland: convenient because they require little to no ongoing care.