Common or garden

I wonder is someone may be able to settle an argument ?

Is the phrase 'Common all garden' or 'Common or garden', and is it possible that anyone knows the origin ?

It's 'Common or Garden' but its origin is not know to me.

I put the phrase in a coupla engines and it seems to mean plain old-plain old as in garden variety. Here is a sentence using the phrase:

"In the course of examining the common or garden chilli pepper, a group of American researchers have found clues to new painkillers."

I have no clue as to its origin.