3, forming mats submerged in deep and emerged in shallow water or on soggy soils. Hottonia, however, is suitable only in water with low hardness. Ranunculus aquatilis is a short lived species that can cover the pond’s surface in the first seasons and completely disappear in others. Salvinia natans will only survive in winter in continental climates when it can lodge between dense reeds.
Special applications of wetland planting
Artificial bogs and wetland
In nature, extensive bogs often occur without any connection to open-water surfaces. This principle can be transferred into urban landscape design. An artificially sealed swamp- landscape corresponds to a man-made pond containing only zone 1 and possibly zone 2 plant communities. It must be remembered that when the whole volume of the swamp bed is filled with substrate, the transpiration of plants and the evaporation of soil will dry out the swamp body very rapidly in summer. The volume of the substrate pores is too small to store enough water for a dry period. A certain amount of water should therefore be stored in covered hollow bodies (Maier 2000:16-18), as shown in Figure 8.20. These bodies can be plastic-pots, buckets turned upside down or canisters. They are to be drilled at the top and bottom, so that water can flow in and out. More than half of the volume should be filled with these hollow bodies, saving substrate and optimising the water balance. The depth of swamp beds is recommended to be between 40-50 cm, if tall forb communities are to be established, or 30 cm for bog or fen vegetation.