Eradicating duckweed (Lemna minor)

[fishkeeper]

Splitting hairs are we?

But thanks for the correction!

But the take home message is. Reducing nitrogen is not going to stop azolla the way it might phase duckweed.

 

[grunsven]

Adding Azolla to fight lemna does not sound like the smart thing to do.
Have you ever measured nitrogen and phosphorus in your pond?

 

[JWERNER]

Just start mailing it to me!


I would look into the placement of the pond itself. I can use duckweed in the terraium and it is nitrate lack do to the other plants in the tank but since it is in direct light it wll still grow regardless of the lack in nutrients.


If you look some ponds just get hit hard no mater what and some just dont at all. In most cases the ones that have no shade at all are the ones to get nailed by the duckweed the most.

 

[TristanH]

Hi,

In my experience, the only practical way to control duckweed is by netting. Fish and ducks are a non-starter with amphibians, as are herbicides. They also increase nutrient levels. Covering the pond basically involves starting again and again will cause deoxygenation and release of nutrients (much the same effect as the duckweed really).

That's the bad news. The good news is that it IS possible to get rid of duckweed by assiduous and frequent netting - but like any invasive plant, don't let quantities build up. And net the pond in autumn to intercept falling leaves.

A healthy community of pond plants will help to absorb the nutrients on which duckweeds thrive. In particular, rooted species such as pondweeds, milfoils and water lilies are good. Free-floating plants that are much easier to control include water-soldier (Stratiotes) and frogbit (Hydrocharis morsus-ranae). I have some spare if you need any (all UK native) - pm me if interested.

Tristan