South Africa has a diversity of aquatic plants
There are two basic types of plant used in NSPs: emergent or marginal aquatics, which typically grow on the shallow edges of water. Reeds, sedges, restios, grasses, bulbs, groundcovers. And submerged or true aquatics, which grow on the bottom of rivers and lakes, such as water lilies, waterblommetjies and potamogetons.
Marginal plants cannot be fully submerged, and have very specific hights at which they need to be be planted. It all has to do with the species’ ability to transport oxygen to their roots. We refer to the junction between the stem and the root as the ankle of the plant. Most sledges like the cyperacea can tolerate their ankes being way below water level, at shin or even knee hight. But some species like the restios will drown if they have more than their toes in the water.
Marginal plants can be planted in gravel and generally do not need soil to thrive. They need to be regularly trimmed to look their best and more aggressive species such as the water parsnip need to be regularly contained or they will take over other slower growers.
True aquatics usually grow from a soil substrate which contains high nutrient levels.