In amongst the cord grass on the mudflats and coastal marshes of Dorset's natural harbours you can occasionally encounter a flower that looks a bit like cow parsley. It is another of those hard to identify members of the carrot family with umbrella shaped clusters of flowers. The fact it is growing on salt marsh, however, can lead you to a pretty positive identification straight away, parsley water-dropwort (Oenanthe lachenalii) is almost certainly the only one that thrives in such habitat.
Being restricted in its preference for habitat this is not a common plant in the United Kingdom but around Poole Harbour one encounters it quite frequently from June until September. It once occurred on inland fens and marshes but loss of that sort of habitat means this flower is now generally confined to coastal mudflats.