Posted: 08/05/2014 at 17:25
I once had a large deep pond one end of which was overhung by a large old yew tree - despite our best efforts no oxygenating or marginal plants would grow there - the only things that fringed it's banks were nettles and willowherb.
We had other ponds on the smallholding all of which were the homes of lots of wildlife including Gt Crested Newts and frogs, with frequent marauding visits by grass snakes. However, the only wildlife I ever saw around this pond was a pigmy shrew catching a beetle on the bank. Even the ducks and geese weren't interested in it.
In every respect it appeared to be a perfectly normal pond, but the water was black and sludgy, anaerobic and dead. The only thing I could attribute it to was the many years of yew leaves which must have poisoned the water somehow.