There are many hard core veg growers out there who don't leave space for any flowers on their plot. It's a kind of old fashioned and macho way of thinking to say that a plot has to be purely productive and that any space taken up by pretty things is a waste. Some of these horticultural despots may find space for a couple of rows of dahlias but apart from that it's function, function, function all the way. I mean, these lot are so strict that they only grow veg in straight lines - can you imagine?
I love growing veg and agree that a plot should have some degree of function so that you can make it as productive as possible but I love growing flowers and think that anyone who doesn't find space for them is really missing out. Aside from many flowers playing an essential part as companion plants keeping pests at bay as they try to attack your other crops there's nothing better than a veg plot that looks as delicious as the veg it produces tastes!
Take these cosmos for example. They're easy as anything to grow from seed and will keep on looking great all summer long if you're sure to keep dead heading them. They'll even produce enough flowers for you to liberate at least a few to take home and make your house look beautiful. You may not be able to eat them but I'd say lovely flowers like this should be an essential part of any veg plot. It's the first time I've grown cosmos from seed this year but I'll certainly be planting plenty more next time.