Wetland and water sites should be planted from May to mid-July. Before this period, temperatures are too low for satisfactory establishment. Later planting means that slow – growing plants, in particular, are not able to fix themselves sufficiently, and winter frost can lift them easily out of the substrate. Potted reed species can be planted until August, whilst bare-rooted water lilies can be put in at any time up to June.
Nearly all perennials, apart from ferns, can be established by sowing, if seeds are available. Some seeds will need to be broadcasted as fresh as possible (Symplocarpus, Rhinanthus and Pedicularis). Many species need a period of cool temperatures, around 0°C-+4°C for at least four to six weeks, to break dormancy (Kircher 1994). The best option is to sow in late autumn, but this is only suitable on sites that will definitely not be flooded in winter or spring. Otherwise, seeds can be mixed with moist sand and stored at the temperatures mentioned above. When the site is no longer flooded, seeds can be broadcast. A thin cover with sand fixes the seed and prevents it from drying up. It should not be thicker than 1 cm because several wetland plants need light to trigger germination.