In common with other chapters in this book, the starting point for the consideration of naturalistic wetland plantings is a consideration of naturally occurring ‘model’ or ‘stereotype’ communities that might provide the basis for modified designed vegetation types. Figure 8.6 shows possible vegetation sequences in five different types of lakes in Central Europe. In very simple terms, we can distinguish three broad vegetation groupings within water bodies themselves.
1 Submerged zone. Submerged species can live as ‘hydrophytes’, fixed by roots into the ground (e. g. Potamogeton, Myriophyllum), or as floating ‘pleustophytes’ (Ceratophyllum, Utricularia).
Organic-shaped natural ponds convey the impression of distance in
space (LWG Veitshochheim, Germany)
Small pond in the author’s garden with water lilies and shallow-water zone. To get the best visual effect, it is important not to cover the water surface too densely with plants
Formal ponds allow the development of a multitude of several habitats on small space—here a raised bed for water lilies is surrounded by L- shaped swamp-beds at the Anhalt University for Applied Sciences, Bernburg, Germany
A formal concrete pond in the botanical garden at Wurzburg,
Germany: water lilies and helophytes are raised up in pre-cast concrete units. The rampantly growing Typha species are kept from spreading by being planted in enclosed receptacles
Potamogeton perfoliatus can grow in water up to 6 m deep. Under nutrient-poor conditions, carpet-forming Characeae are typical, whilst in eutrophic water stands of Myriophyllum or Elodea are found. Water pressure and light intensity determine a plant’s ability to grow in deep water. In oligotrophic water, submerged plants can reach deeper zones than in more eutrophic waters because lower levels of floating algae mean clearer water and greater light-intensity at depth.
2 Floating-leaf community. Rooted hydrophytes, such as Water Lilies (Nymphaea) or
Nuphar, and floating pleustophytes can be found here also. The roots of the latter hang into the water without being fixed into the bottom (as in Hydrocharis, or in the tropics, Eichhornia). In eutrophic and hypertrophic water, Duckweed (Lemna minor) forms dense carpets and shades out sunlight, reducing the abundance of submerged species.
3 Emergent aquatic plant communities. ‘Helophytes’ are those plants that are rooted
underwater or in saturated soil but with stems and leaves that rise at least partly above the water surface. Whilst a species such as the Tall Rush, Schoenoplectus lacustris, can grow in 3 m depth of water, many Carex species or Iris sibirica will survive in only temporarily flooded wet meadows. The most common emergent aquatic plant is Phragmites australis, which is found throughout the world and forms extensive reed communities facilitated by rampantly spreading rhizomes. Under hard water oligotrophic conditions, Twig Rush (Cladium mariscus) is typical, whilst in eutrophic water Butomus umbellatus, Iris pseudacorus or Typha angustifolia are common and in very nutrient-rich water, Glyceria maxima or Bolboschoenus maritimus are common. In a zone of fluctuating water, often a belt of Tufted Sedge (Carex elata) occurs in front of the real emergent plant community. Under oligotrophic or mesotrophic conditions a very special shore vegetation can develop: rhizomes of Eriophorum angustifolium, running Carex species, Potentillapalustris and Menyanthes trifoliata grow out, floating upon the water surface. They can produce a dense blanket that may be settled by other plants, forming what is in effect a floating meadow.