The name English stonecrop (Sedum anglicum) says it all really, this is a species native to our shores that grows by clinging to rock surfaces by the sea. Its ability to grow on stone means that quite often you will see it on garden and house walls in seaside locations. It is our commonest stonecrop and it not only grows naturally in the wild but is a popular plant for garden rockeries and so it can 'crop' up almost anywhere.
Often forming quite large blankets of reddish stems topped with small white or pinkish star-shaped flowers they create a petty sight. They do not have leaves in the accepted sense, instead they look a little like a series of pale green buds linked together. I am not sure that is a good description but it is the best I can do.
In recent times sedum have become a popular insulation for roof tops where it is encouraged to grow across the roof surface thus forming a blanket to keep the heat inside the building. English stonecrop is at the forefront of this new 'technology'.English Stonecrop: star walls