I live in Massachusetts and have a swath of pachysandra approximately twelve inches wide growing against the foundation around my house. It's healthy and produced a lot of pretty, sweet-smelling flowers throughout the summer.
We recently trimmed a section and, as you can see, there's a green substance on the concrete that looks like algae. Is the pachysandra causing that? Is the algae dangerous to the concrete? If so, is trimming the plant enough or do we actually have to dig it up? One of the reasons we like it is because it hides the ugly foundation, so I'll leave it unless advised otherwise.