There is a small pond on the allotment. The thought occurred to me that it would be nice to have some Yellow Flag Iris (Iris pseudacorus) which grows wild in the UK on marshy ground. Accordingly I purchased several clumps by mail order and put them in a pot sitting in the pond itself to keep the soil permanently moist.
 On a summer day a number of years ago I was walking through a secluded valley in Dorset. The valley had a soggy bottom (so to speak) and there were Yellow Flags in flower all along it: