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Duckweed: Friend or Foe?

A lot of people get worried when they see signs of Duckweed; but should it be encouraged rather than treated?

18 September 2017
Duckweed: Friend or Foe?

If you have experienced Duckweed in your pond then you may feel quite passionately about how much of a nuisance it can become over time. Once introduced it becomes very tricky to remove, so if you have experienced it once then you are probably still experiencing it! We regularly meet pond keepers desperate to rid their ponds of the tiny green plants, but from time to time we also meet individuals that want to introduce it to their pond environment.

This led me to wonder what the positives of Duckweed could possibly be?! After a little research I started to realise that this multiplying annoyance is actually quite wonderful. So I’ve compiled an argument in support of the multiplying weed.

Duckweed is high protein. In fact it contains more protein than soybeans. It is an ideal food source for waterfowl, but in the USA they are experimenting with using it as feed for fish and pigs. Amazingly in some parts of Southeast Asia humans eat it. You may not wish to start cultivating your own high protein snacks in your pond, but it is certainly useful to know it could become potential sustenance for your surrounding wildlife environment. (For further ready on the cultivation of Duckweed for sustainable protein and fresh water reuse see Tamra Fakhoorian’s blog)  

Duckweed stops algae growth. Yes, that means Duckweed will stop Blanket weed. It grows rapidly and uses up excess mineral nutrients, particularly nitrogen and phosphates. It removes nitrate from water and can be considered a water purifier. For many pond keepers, removing algae with another evasive plant may perhaps seem bizarre, but if kept under control it can benefit your pond water rather than suffocating pond life. The Swiss Department of Water and Sanitation in Developing Countries, associated with the Swiss Federal Institute for Environmental Science and Technology claims that Duckweed can be used for wastewater treatment to control odour and toxins, which in turn will prevent the development of algae and the breeding of mosquitoes. To further this belief in its amazing clarifying power, the USA is currently experimenting with the use of Duckweed as a stage of treatment for human sewerage.   

Duckweed with long roots

The aesthetic benefit goes beyond the simple addition of green to a pond surface. Duck weed can be cunningly used to disguise parts of your pond that are less desirable to the eye such as blending the marginal plant baskets into your pond surroundings. If you regularly struggle with pond water evaporation in the summer months then a covering of Duckweed will reduce this for you, whilst providing shelter and shade for pond water species.            

The most astonishing discovery of Duckweed, albeit still in a theoretical stage, is that it can be used to monitor the health of your pond. The length of the Duckweed root has been proven to have direct relation to the amount of nutrients in your pond; the fewer the nutrients the longer the root. Therefore the longer the root the better!

If you’re now thinking that you’d like to add some Duckweed to your pond, you’ll be happy to read that it is believed to be the fastest growing plant with the ability to double its biomass in ten days. So you won’t need to wait too long to benefit from all of these attributes.  

You may be wondering at this point how it can possibly be kept under control if it grows so quickly. It does involve regular maintenance with repeated raking, netting and removal of the weed (removed Duckweed can be composted). Also shading can reduce growth so planting on the south side of your pond or adding waterlilies with floating leaves can assist. Duckweed likes still standing water so anything that disturbs the water surface such as a fountain or air pump may also help. Lastly excessive nutrients in your water will cause the Duckweed to thrive, so cutting down on things that will cause this (over feeding of fish, garden fertiliser leaking into the pond etc) will also help.

However if at this point you are still not convinced that Duckweed is right for your pond then it is worth knowing that we offer a treatment that will help eradicate the weed from your pond: Blagdon Duckweed Buster. It has surprised me to discover that something considered to be such a problematic weed can be of such benefit to your pond water, wildlife and surrounding environment. Duckweed is certainly a misunderstood plant. Hopefully you will now see Duckweed in more of a friendly light whether or not you choose to include it in your pond habitat.  

As always, if you’d like to discuss your pond problems directly with a member of our team, then please email us on

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