These are plants which prefer wet conditions, waterlogged and clay soil or that like marshy conditions close to water. Many Aquatic plants will be suitable here too.
Marshy areas don’t have to look dull and dreary, use the following plants for different textures and heights and they will love the moisture as well. Acanthus mollis’ big leaves and flowerspikes and Ajuga. Bamboo loves a wet area. All Sedges, for example: Carex x ‘China Blue’, C. alba ‘Sea Green’, C. lurida ‘Silver’, C. comans ‘Frosted Curls’ and C. comans ‘Select’, C. hachijoenensis ‘Evergold’, are well adapted for wet areas. Also use Lamium, Mentha requienii, Muehlenbeckia axillaris and Miscanthus species that give a lovely texture and colour, Musa ensete ‘Ventricosum’ for a big statement to a troical effect as well as Pogonantherum paniceum.
For flowers and colour in soggy, wet spots, use Coleus, Crinum macowanii, Hemerocallis, Hydechium, Impatience ‘New Guinea’, Iris confusa, Kniphofia, Lysimachia atropurpurea, Oenothera berlandieri, Persicaria amplexicaulis for a variety in leaf colour as well as flower, Ruellia brittoniana, Viola hederacea.
For the tree section we have Acer rubrum, Populus lasiocarpa and Populus simonii ‘Fastigiata’. With these trees, one has to plant them a good way off from the water’s edge- -/- 5m away or at least 2m above water level. That being said, other trees would die of suffocation as their roots would need more aeration to survive.