Water Lilies
Water-lilies are are characterised by their circular floating leaves and white or yellow flowers. They grow at the edges of slow flowing rivers, in canals, lakes and ponds. They can grow in water of up to 5m deep, but prefer depths of between 1m and 3m.
Nuphar lutea (Yellow Water-lily) and Nymphaea alba (White Water-lily) are the most frequently encountered species with Nuphar pumila (Least Water-lily) being less common.
N. lutea (Yellow Water-lily) is common in rivers and, unlike N. alba, produces submerged as well as floating leaves. In faster situations the floating leaves of Yellow Water-lily are sometimes absent and the plant has been called "Cabbage-lily" because of the appearance of the submerged leaves. It is also commonly known as Brandy Bottle because of the shape of the flower buds. The White Water-lily is becoming rarer and therefore has conservation value. The species can be distinguished before flowering by the different shaped floating leaves. Nuphar species have an oval shaped floating leaf and Nymphaea species have a round leaf which overlaps slightly behind the stalk.
Water-lilies have extensive rhizome systems from which leaf and flower stalks emerge each year. The plants spread only slowly. Water-lilies are often preserved because the leaf stalks have little effect on flow and the shading effect of the floating leaves helps to suppress the growth of more troublesome submerged plants. However, if left unchecked they can produce a dense cover of the water surface and control is sometimes necessary. Where control is necessary, some plants should be left along the margins or in localised clumps where they do not cause a problem.
Control
Mechanical control - Cutting, followed by the removal of the leaves to prevent de-oxygenation can be done with our Truxor amphibious machine.
Cutting should be carried out as late in the season as possible to reduce the risk of regrowth.Dredging can be carried out at any time of year but may be more effective in summer when the location of the rhizomes can be detected by the presence of floating leaves.
Chemical control - Spraying the floating leaves of Yellow and White Water-lilies with glyphosate is a very effective method of control. This technique cannot be used on the Yellow Water-lily when only submerged leaves are present (usually in fast flowing situations). Glyphosate can be applied to achieve localised control to create a clear channel down the centre of the river or a clear patch in a lake while retaining a fringe of Water-lilies at the margins.
Our qualified boat operators can provide this service.
Biological control - Ducks are renowned for their appetite for the buds and submerged leaves of Water-lilies. Increasing wildfowl populations will have a marked effect on the amount of Water-lily growth.
Environmental control - Shade is an effective method of control for this species.