I put some Mizuna seeds in and around this area, and this has sprung up:
(http://i122.photobucket.com/albums/o246/cosmoanddibs/Image017.jpg)
Is it a weed, or is it the Mizuna? I've looked on Google Images for 'Mizuna seedlings', and the picture doesn't match.
???
Have you got raspberries or blackberries nearby because that looks like a runner.
I'd agree - looks like a raspberry to me
Raspberry canes are just inches away from this area. Do I just leave them to grow?
If you leave it, it will grow but do you want it there? A weed is just a plant in the wrong place... :-\