Wednesday, 19 September 2012

We must talk about...blanketweed

...and newts!

To many gardeners, it’s the green scum that needs to be regularly dragged out of the water with a thin tined lawn rake. To us, it is a haven for wildlife, providing both habitat and nutrition for a wide variety of insects and amphibians. 

Blanketweed is a filamentous algae whose new growth arises from the depths each sunny morning glistening with purifying bubbles of oxygen. We love watching baby frogs hopping on the green surface carpet and on to the water lilies and water soldiers. 

Blanket weed ‘sucks’ unwanted nutrients from the water including all those nitrates when we top up with tap water. As a result the pond water is crystal clear.

Rather unwittingly, we have created ideal conditions for crested newts. My no-dig methods, along with the use of glyphosate, leave a rich weed free vegetation and liverwort, pearlwort and moss encrusted surfaces. 

My favourite sandstone mulching and edging stones are loosely bound together by liverwort and provide places where newts might hibernate. The herons have made their own contribution. We have no fish!

Water snails love the blanket weed, and their general scavenging helps keep the pond clear. It’s fascinating watching them feed.
Newts like a land habitat too.
For most of their lifecycle newts need open fields and cover. They move seamlessly between the farm fields, my unfenced garden and the big, unlined breeding pond next door. In August the newts will have been feeding amongst the blanket weed. It would have been cruel and foolish to skim it away! Now in September, it is safer and I will drag out bundles of blanket weed, excess oxygenating plants and Autumn leaves. 

It is absolutely essential to avoid too much vegetation which, if allowed to decay, deoxygenates water. None of my nine ponds have any filters or pumped circulation.

When I drag out surplus vegetation I do not waste all that lovely organic matter It is left at the side of the pond touching the water. This allows fauna to return to the pond. I throw back the snails. My debris is later ‘lost’ behind plants or goes on my vegetable garden. Most of you will sensibly put it on the compost heap.

I have a dilemma! Rare Great Crested Newts bring such a responsibility! Last summer, brother-in-law Dave built me a beautiful stack of drying logs. It must make a wonderful newt hibernacle. Perhaps the logs will never be burnt!

(above: juvenile Great Crested Newt eft) Great Crested Newts move in and out of breeding ponds, as well as between ponds, over spring and summer. Most will have left the water by August and emigration from the pond usually coincides with periods of rainfall. Most newts are dormant by the end of November. A good overwintering site may be a void in a tree stump or bank, or under refugia such as rock piles or dead wood. Juvenile newts are known to emerge from ponds around August and September, and there is some evidence that they recognise and follow the scent trails of the adults to find high quality foraging habitat and refuge. For successful emergence, ponds should retain water and be left undisturbed until at least the end of August. 


  1. Interesting post Roger, I have learned something today.

  2. Blanket weed is a symptom of pollution which comes from tap water so to make your garden pond better for wildlife start off with the cleanest water - rain collect in water butts and refill your ponds with rainwater rather than potentially really polluted water from the tap.....

    1. Thanks for your helpful comments Jon.
      Unfortunately on my windy site, without tap water I would have no ponds. As mentioned in my blog I do not dislike blanketweed, it helps keep the water clear. It is easily removed when in excess with my trusty lawn rake. I do not regard my pond as polluted even though tap water does contain nitrate, quite a lot actually.
      My neighbour's large natural pond which never sees tap water or receives farmer's fertiliser is full of blanket weed. This pond is probably loaded with nitrate from the numerous birds and their droppings. Similarly I would suggest water collected from roofs is also rich in nitrate from bird droppings.
      Had a look at your interesting blog, Jon.

    2. Nitrates are not the best stuff in the world but I'd hesitate to call it 'pollution'. We have blanketweed at certain times of the year (usually midsummer) in our big, natural wildlife pond. We don't even bother to rake it out because it's always heaving with GCN. The young newt fry use it as cover from predators. As far as I'm concerned, a bit of blanketweed is good for all sorts of pond fauna.

  3. Blanket Weed is a pain for most Koi pond keepers, but like your post says it sucks up nutrients really well so why not enhance it's power and grow it in an area of your pond under control or maybe build an open top filter to allow it to grow in full sunlight. Marine hobbyists do something very similar in sump filters and the results are very good.

    Holiday Aquatics

  4. Hi Roger, I really like your blog it was awesome I really get some new thing to learn. As blanketweed problem is a big headache to get rid off. I have seen a video on YouTube is which it showing a product which easily and rapidly removing blanketweed and also helps to prevent it. I think you should watch that video .It was amazing product..

    Link :


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