My neighbour emptied a great deal of his koi fish pond water which came like a waterfall into our garden. Several areas were flooded for 24 hours and all this on top of the highest rainfall we've had for years in the UK. It virtually hasn't stopped for nearly 3 months! Up 'til now our plants have coped, although blooming later than normal due to low sunlight levels, I guess, but after the pond water incident, several have died, notably Japanese anemones, some fuchsias, geraniums and a few others. Was it just that the water from the pond was the last straw, or was it the chemicals that were undoubtedly in the water? Suggestions please. On a happier note, we have just returned from the Olympic Park in London after watching a morning of athletics. The planting in the park was stunning, nearly as good as the sport - swathes of agapanthus, kniphofia, meadow flowers of poppies, cornflowers and marigolds. Wow ! The whole experience was wonderful: everything very well organised, no queues, friendly security (especially our armed forces who stepped in at the last minute), helpful volunteers and good fish and chips! Anyway, back to gardening...
If your neighbor was raising koi in his pond, I don't know that there would have been a ton of chemicals in there that would hurt plants since they wouldn't be good for the fish either. So I'd be inclined to think that the extra flooding on top of already having excess moisture was probably the main culprit.
Glad you enjoyed getting to see some of the Olympics!
Ecrane is correct, the water from the pond that fish have been happy living in would never have chemicals in it, the fish would never survive, however, have you checked with the neighbours to ask why they emptied the pond all over your place, why did they now use a hose pipe to drain there pond or ven bucket's to empty, sure I know it takes a while to empty the pond but hey!!!! when you have a pond you also take on the responsibility to make sure water does not leach out onto the next doors garden / drains / buildings etc.
The other think toy find out is, WHY did the empty the pond, did someone put chemicals into it by mistake, did the pond spring a leak WHY !!!! if they are decent people, they should have came to check where there pond water was going even if by accident, ponts (even small ones hold a fair amount of water so I'm not surprized your property was flooded especially on top of the rain we have had in this country and some area's have had to abandon their homed due to flooding, GB has had the heaviest rain fall in some areas sinse records began so not surprising your plants have not survived.
The plants you mention that have sucumbed to the water are to be honest, all plants that prefere drier conditions, that is why we can grow them best in summer, (summer bedding we call them) they need heat, drier conditions than some other plants and lots of sunlight, everything you have not been able to give them, the pond filled with alge and fish poo, fish food etc would not have killed the plants but would have certainly been the last straw as most of these plants are grown in tubs / basket/ containers and are normally best suited to planting out here in UK between end of May and are normally finished flowering just as the first frosts arrive around October / November. however some people who have greenhouses or indoor space take these bedding plants inside under cover and keep them barely damp ?almost dry till the following spring when the feed them, prune them and start them off for the following summer show,
The summer rain we have had has put paid to lot's of peoples bedding displays so perhaps that has also had detrimental effect also, maybe next year will be kinder to us UK gardeners eh.
Good luck Tigerlily hope next year is good to you.
Only if they put an anti-algae chemical in the water would it have bothered your plants. I actually water my plants with the pond water from my ponds...free" fish emulsion makes things nice and green and is an organic fertilzer! :)