RAUK - Archived Forum - The Devil (duckweed)

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The Devil (duckweed):

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ben rigsby
Senior Member
Joined: 27 Apr 2010
No. of posts: 337


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Posted: 27 May 2010
other than trying to keep on top of it by scooping with a net as best you can regularily, what eco-safe methods do people have for dramatically reducing, or better still eradicating, DUCKWEED?
in my amphib pool ive got plenty of other native plants for competition so it hasnt taken complete hold but its a constant threat to the eco-system (light blocking) and to my enjoyment of the pond too. its so difficult with a net to ONLY remove duckweed. ive heard of someone using suction for removal? what with? anyone tried it?
ive had years of laborious scooping and im fed up with it. garden centres havent helped much.
can you eat the stuff? i know a larger species is grown as salad.
all (if any) non-toxic suggestions welcome!
ben
Diversity.
herpetologic2
Senior Member
Joined: 15 Jun 2004
No. of posts: 1369


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Posted: 27 May 2010
Draining the pond and starting again may be the only way to
get rid of it. Dig a new pond fill in the old pond and
leave fallow for several years - make sure that the pond
plants placed into the new pond has no duckweed or allow
for natural regeneration or colonisation by wild plants.

regular harvesting and composting of the duck weed is great
for the garden or veg patch

J
Vice Chair of ARG UK - self employed consultant -
visit ARG UK & Alresford Wildlife
Suzi
Senior Member
Joined: 06 Apr 2005
No. of posts: 860


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Posted: 27 May 2010
I got duckweed in my pond after 3 years, brought in on the back of frogs from a neighbour's pond! I saw it on their backs and figured it out. I would say it is well nigh impossible to get rid of if you have other weeds as it gets in amongst them.
I brush mine out by running a nylon hearth brush across the surface and shaking the weed onto the pond edge. The pond only stays clear a day or so but doing it daily only takes 5 mins or so (small pond). I can't do it at the moment as my taddies are all in amongst it.
Once cleared I can watch the newts in the water which the duckweed totally obscures of course.

Suz
Caleb
Forum Coordinator
Joined: 17 Feb 2003
No. of posts: 448


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Posted: 28 May 2010
Masses of duckweed is usually a symptom that the pond water is excessively rich in nutrients.

A pond will obviously gain nutrients if its inputs are greater than its outputs. Nutrient inputs might include things like topping-up with tap water, adding fish food, new plants, soil, bird droppings etc.

Losses in nutrients will only happen if organic matter (plants, mud at the bottom of the pond) or nutrient-rich water is removed. There are various ways this will happen in the wild, but in a garden pond, you'll have to manage it yourself.

A local pond had 100% duckweed coverage, and dead leaves about a foot deep at the bottom- removing most of the dead leaves reduced the duckweed to almost nothing in one season.


Suzi
Senior Member
Joined: 06 Apr 2005
No. of posts: 860


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Posted: 28 May 2010
Thanks Caleb for that info. I would say I don't have any of the nutrient inputs you describe except probably mud at the bottom of the pond. I was also careful not to add water from the hosepipe as I knew that added nutrients. However I do now occasionally top the pond up with the hose as I figure I got the duckweed anyway! I thought mud at the the bottom of the pond was good for the pondlife but maybe I ought to remove some. 
Suz
lalchitri
Senior Member
Joined: 06 Jun 2006
No. of posts: 132


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Posted: 28 May 2010
This year my pond is also fully covered with a thick blanket of duckweed.
Like suzi I am also reluctant to net it out, due to the large number of tadpoles amongst the weed.
Since the tadpoles seem to be faring well I am leaning towards leaving it at the time being.
Though they seem to be developing slower due to the lack of sunlight, I suppose it is a good source of food.


Reformed Teetotaller
ben rigsby
Senior Member
Joined: 27 Apr 2010
No. of posts: 337


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Posted: 28 May 2010
thanks folks!
some great info and thanks for the brush tip suze- i hadnt considered that approach. will see if that works better than my hand net.
your pond sounds similar to mine in some ways. it too has had none of the nutrient-giving sources listed by caleb in his excellent background info. so i dont think my pools "running rich".
i prefer to interfere with it as little as possible for the animals sake.
however, i HAVE considered aspects of herpetologic's drastic (but probably necessary) option. again though, im very reluctant to disrupt amphibian breeding cycles. i dont really have the space either.
nice compost tip though cheers.
it sounds like im stuck with duckweed for now. hopefully they will come up with a safe binding agent soon. like the one currently used for blanket weed!

TOGETHER, LET US PRAY..........



thanks, ben

PS suz- Froglifes GCN Conservation handbook suggests deep mud is good for amphibians.
Diversity.

- The Devil (duckweed)

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