Phacelia about to flower - what now?

I sowed some Phacelia as a green manure a couple of months back expecting it to get frosted and then rot on the soil over winter preventing weed growth. however it's about to flower and was wondering what the best thing to do with it was? Options include; Cut it down completely, just cut off the top bit so it grows a bit more bushy. Don't fancy digging it in yet as then weeds will start growing.

leaving it never presented problems for me (compared to weeds)