Wells are dressed by creating pictures or scenes out of petals, leaves, twigs and other natural things such as wool and string. These are pushed into wet clay and it is quite an acquired skill. Volunteers will spend many hours working hard to get the picture finished on time, often working through the night in shifts. The whole thing is mounted on a framework and this is erected at the site of the village well (or at several wells in one village).
Originally the purpose was a pagan tradition to give thanks for pure water. Nowadays the custom is carried on with a religious theme. There is usually a service in the village church for the blessing of the well when the dressing is erected and it will stay in place for about a week. After that the components deteriorate and the structure is taken down.
There are now many more villages doing this than when I was a child. From May until September you can find at least one village every week that has its well dressings on display. It is also a great attraction for tourists to the county.
Usually there will be several well dressings in each village and some other kind of entertainment going on; typically, at the very least there will be refreshments and craft sales in the village hall.