Perennials: Uninvited, 0 by Maria

Maria wrote:
Two years ago this yellow flower came ununvited in to my garden, I left its single
yellow blossom alone because it looked very pretty. Now look what mass of flowers it turned out be and I have no idea how it got there nor do I know its name.

The other flower in the second picture with the yellow flowers is also one I am not certain of its name, it was purchased at a GC sale and never came home with the Tag
Maria