There are three main types of
duckweed from the point of view of control,
Lemna minor,
Lemna minuta and
Lemna trisulca. The first two float on
the water surface, while the
third is a submerged free-floating plant that does not usually cause problems.
Duckweeds can be
controlled by increasing the flushing rate of your pond. Outlet weirs have
to be specially designed to encourage removal of floating weeds.
Duckweeds can be
controlled by reducing the amount of organic debris in your pond (See
Lavaris Lake System
- ClearLake or Siltex).
The most important thing
to do is remove them as soon as you see them in Spring. They grow by
division, and can double in 3 - 5 days, so reducing the amount you have at the
start of the season can have a very big effect on how much you get at the end of
the season.
Increasing disturbance of
the surface of the water can also help, especially for Lemna minor, which
will clog together and sink. If you have Lemna minuta, this will
not work and you will have to skim it off, add Clearlake or Siltex and remove as
much as you can in early Spring.
