Plant Doctor Archive

Water Gardens — Controlling duckweed

HOW do I get rid of irritating duckweed from my pond?

WITH great difficulty! This small floating, light green fern will grow profusely in ponds and can regenerate with alarming speed from only one or two small pieces. It will be more of a problem in ponds that have an excess of nutrients, so sensible stocking, feeding, filtering and partial water changing will help.

Goldfish will also eat it, but not as a first choice, so keep them hungry if you have this problem. Having said all this, it probably is true to say that the only way to eradicate duckweed is to physically remove it. Net it off, net it off and net it off again. Repeat this procedure about 500 times and you should be getting there! As you can see, it is easier to prevent the problem in the first place. If you spot a few pieces - and it is virtually impossible to keep it out completely - then remove it while it is still only one or two pieces.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.