16-001014-02A (Ultimate SCMMP)

Submerged weeds
Submerged weeds are aquatic plants that are rooted
in the substrate and fully, or almost completely,
submerged. These plants are characterised by leaves
that are located either below or at the water surface.
The leaves and stems have specialised thin-walled cells
with large air spaces that provide buoyancy and support.
The lack of a waxy cuticle on the plant surface allows for
the rapid exchange of water, nutrients, and gas; however,
the plants are highly susceptible to drying if removed
from the water for any length of time.

Dense infestations of submerged aquatic plants can
be physically removed using hand pulling, raking, or
mechanical equipment, but the major submerged
weeds quickly regrow unless their roots are removed.

Most submerged plants spread easily from fragments.
All stems and roots should be completely removed from
the water body, as any residual fragments will result in
re-establishment and the potential spread of the weed
to downstream water bodies.

Care must also be taken to ensure that rigorous hygiene
protocols are followed, so that the weeds are not spread
to other water bodies. All removed plant material should
be relocated well away from the water body and buried,
or dried and burnt.

Most submerged aquatic plants are highly sensitive to
drying out. Drawing down the water level in a water body
and allowing the substrate to completely dry out can
provide effective control.

Herbicides can be used for controlling submerged
aquatic plants. The application of herbicides is difficult
due to the problems associated with applying chemicals
in water and the potential impacts on non-target plant
species. Seek advice from the relevant authority if
chemical control of submerged plants is being
considered.

Small areas of submerged aquatic plants may also be
treated by increasing shade. This can be achieved by
covering the surface of the water body with a lightproof
cover, such as black plastic sheeting for a month or more,
but this method is usually impractical.




                                                             Maintaining Vegetated Stormwater Assets Version 1   67