Pond water gets Yellow Flag!

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Iris Pseudacorus, the ‘Yellow Flag’

Despite the annual invasion of amorous frogs and toads, and the trio of Mallards which have decided to stay rather longer than they usually do, the water in the pond has returned to crystal clarity. Our web-footed friends have been doing some weeding in the pond so the oxygenators have been thinned and the water lilies are, shall we say, a little behind this year, but they are still alive and will hopefully recover from their trimming! That said, I note that the Brandy Bottle, the yellow water lily look-alike, Nuphar luteum, is now in flower (with its curiously alcoholic scent so attractive to flies), so this fills me with some hope that the other water lilies will follow suit shortly!

Under the water, there is much activity from a wealth of insect larvae, diving beetles, pond skaters, tadpoles, caddis fly larvae, bloodworm, not to mention our colony of endearing smooth newts of which there are many. It’s the breeding season at the moment and they can be seen displaying to each other waggling their tales furiously!

It’s great to be able to see all this wealth of pondlife but it’s only the last couple of years that we’ve had clear water. Previously, it was pea green with zero visibility and not much of an attraction! The water clearly wasn’t ‘balanced’ – too many nitrates, not enough plant matter to use it up, so the algae took over.

The game-changers were the Yellow Flag irises (I.pseudacorus) which we put in the pond a few years ago; they are greedy consumers of nitrates and as their clumps have gradually expanded, they have served to filter the water to perfect clarity. Much cheaper than running pond filters with UV clarifiers and no maintenance, although on warm days at this time of the year, they do ‘drink’ pond water by the gallon, necessitating a top-up with the garden hose from time to time!

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Nuphar luteum, ‘Brandy Bottle’

Now that the water’s clear, it’s very tempting to re-stock with a few choice goldfish or the majestic golden orfe. But we would say farewell to much of the pond life as the hungry fish hoovered it up, the water almost certainly would return to its ‘pea soup’ consistency, and before long, Mr Heron would return looking to feed his family, so I think we’ll leave things as they are!

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6 Responses to Pond water gets Yellow Flag!

  1. Well I learned something here. The yellow iris is a hero plant, providing beautiful flowers and cleaning the water.

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  2. debsgarden says:

    I have always dreamed of having a pond, as much for the wildlife as for the beauty of the water. I think it is very interesting and instructive that the yellow flag iris cleared up your pond!

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  3. Even with plant life we still have algae and a pond weed that is invasive brought by visitors…of course our pond is smaller. Your yellow flag is lovely. Our native flag is blue or a blue-purple.

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