This account is from about 1900 in Derbyshire.
A well-dressing, or well-flowering .. [was] a charming Derbyshire custom which has been revived in many villages of recent years, when the principal wells are dressed with flowers and a simple religious service is held at their side. Here at Roston the school children had walked in procession from Norbury Church, a mile away, with the clergy at their head. Hymns were sung on the way, and again on reaching the well, where the Benediction was pronounced. The Roston Welll – it bears the name of Friday Well – stands in a farm-yard at the back of a little Primitive Methodist Chapel, and … the entrance was decked with branches and boughs of trees, with a rustic arch adorned with cheap flags, large festoons of laburnum and lilac, and a scroll bearing the text, “O ye wells, Bless ye the LORD, Praise Him and magnify Him for ever”. Over the well itself an elaborate structure had been raised, which had evidently kept the good women of Roston very busy for the previous day or two. A large wooden frame had been made, rounded at the top and divided into separate partitions. In the centre was a representation of Battle Abbey, with the outline of the building picked out in haricot beans. A Union Jack waved above it – the red being supplied by geranium petals, the blue by cornflowers, and the white by rice. The background was of moss and other green stuff. Devices were formed out of Indian corn, linseed and small fir cones; daisies in intersecting rings and as borders were a feature of the decoration, and bright colours were obtained from different flower petals. “Peace unto All” was the legend at the top of the frame, and at the foot “God save the King” while a dove of haricot beans spread benign and sheltering wings over all. The whole was a most creditable display of ingenuity and good taste. The frames are coated over with wet clay into which salt has been kneaded in order to keep it moist and adhesive, and the flowers and other ornaments are then stuck on one by one.
The same source describes similar well-dressing at Tissington on Holy Thursday or Rogation day, which has been practices for centuries.
Here there are 5 wells…. Local tradition ascribes the ritual to local cause, then the region suffered from a prolonged drought; rivers dried up leaving wells as the only source of water for the region. But well dressing is found in many other regions, eg St Edmund’s well near Oxford, Droitwich, Worcestershire and Brewood in Staffordshire. .. It is said thad during the Black Death ….Tissington escaped and the people ascribed their immunity to the purity of their water.