Image used with permission of Mandy Barrow from her website: http://resources.woodlands-junior.kent.sch.uk/customs/questions/welldressing/index.html
In the English villages which still practice the craft, it is well dressing time. Well dressing takes place from May to September, is a very old tradition, as the pagan custom of making sacrifices to well gods was later taken up by Christians wanting to give thanks for the gift of water.
Originally, the decoration of wells only involved simple arrangements of flowers and other natural materials, but in the seventeenth century, Tissington and other villages in Derbyshire began to do their wells up much more elaborately to show gratitude for being spared the ravages of plague that struck Eyam. By Victorian times, wells were sporting large framed, picture panels with religious, historic, or locally significant themes, and were made by pressing flowers, leaves, seeds, berries, moss, and other natural materials into clay in a mosaic-style.
Once dressed, wells are blessed, with processions moving from well to well in places that have more than one.
Time Travelling With Kids 
Wells are better dressed than I am. Of course, doesn’t take much for that. I’ve never heard of this practice before. As usual, you’re finding interesting history for us to read.
I’ve known about the custom for a long time, but have never actually viewed any dressed wells as we didn’t live in that area. Any pictures I’ve seen have always been quite lovely though. The one I posted comes from the Woodlands Junior School website, which has a lot of interesting stuff.