Nine Star perennial broccoli

I'd also plant in a group and use one of my myriad bundles of mesh to cover them to keep beasties off, probably using the same area for other brassicas and carrots which would all benefit from mesh protection. As perennial broc is likely to remain in that space for ever (the clue's in the name) next year, if you practice crop rotation, might be different. With no crop rotation you could dedicate that area to protected species and mesh it always growing brassicas and carrots there each year.