this plant overwintered here in Brooklyn NY and I have been lettting it grow to see what it will do- I thought it might be a mutant broc, thought it might be kale- cautious nibbles on the leaves put it in that plant family by its taste. One of them is almost five feet tall!
Well, if it IS a mustard, which it very much looks like, it is pretty nutritious. Growing up in very green surroundings I grew to appreciate the large selection of edible flora, wild mustards being the more tasty. Sadly, wild mustards do not like the hill soil here. :( If you are into herbs or general cooked greens/salad then you can simply control it if it becomes invasive. Otherwise, the flowers aren't unpleasant either.
But this is just my opinion, I'm far more an enthusiast than an expert (thus why I'm here :)).
Okay, cool, I can eat the leaves - the ones from the backyard, where I had the soil replaced. the original soil had concrete over it for years, coal ash from 70-100 years ago, and tested for heavy metals.
The one out front will be thrown out at the end of the season, as I understand brassicas pull the heavy metals out of the soil as they grow. I might as well do this until I get money together to replace that soil as well, and just plant decorative things.
I am also remediating the front yard with Hairy Vetch - gorgeous clusters of purple flowers!
I think it is more likely one of the mustards in the link from nifty as noted in New York. Don't worry over the 'tall' part. All my mustard and brassicas are four to five feet with flowers now. But anyway, try raw or cooked. My raw (cultivated) mustard is very hot and spicy but cooking makes it mellow and delicious.