16-001014-02A (Ultimate SCMMP)

     Floating attached weeds
     Floating attached aquatic plants are rooted to the
     substrate and have mature leaves floating on the water
     surface (e.g. waterlilies). Floating attached plants have
     extensive rhizome systems, from which long stems of up
     to 5 m and leaves emerge each year. Floating attached
     plants often form dense stands, and the leaves are often
     pushed up above the surface of the water.

     Floating attached plants can only be eradicated by killing
     or removing the root system. The roots are strongly
     bound to the sediments and are not easily dislodged.
     Short-term control of floating attached plants can be
     achieved by cutting the stems below the surface,
     however the leaves will regrow. Mechanical harvesters
     can also be used for temporary control.

     Rhizomes may be removed from the sediments by hand
     raking and using dredging equipment. The removal of
     rhizomes is best undertaken during the summer period
     when the location of the rhizomes can be detected by
     the presence of the floating leaves.

     The use of herbicides is also an effective method of
     controlling floating attached plants, particularly where
     the surface of the water is completely covered with
     leaves. Care must be taken that the herbicide is directed
     onto the floating leaves and that any adjacent open
     water areas or non-target plants are avoided.




70                     Maintaining Vegetated Stormwater Assets Version 1