Phacelia is quite prolific. Here is part of my garden last year. 6 weeks after this photo, the place was as purple as the North York Moors at their best, and I had literally thousands of bees, all very civil.
The seedlings are easy to recognize, which is just as well, because the stuff self sows like mad. :)
PS........I have since dug veggie beds, and porch is on its way at the back door. :)