[courgette]

do things like lettuces, carrots, onions flower? Most probably a dumb question, :oops:  but was wondering where the seeds came from if not?

[compostqueen]

yes they do. Some veggies can be left to go to seed which you can then collect and sow the following year. That is if they're not hybrids.  Real Seeds company specialises in these veggies  

[gobs]

Of course they do. Lettuce will flower in the same year, the other two are biennials, so the next season is more likely, but commonly can happen in same year, called bolting, loss of veg. Some vegetable flowers are really pretty, worth letting a few be anyway.

Most likely you won't like that they do.

[Trillium]

I find that onions from sets tend to bolt to seed in the year I plant them so I stick with onion seeds and don't have that problem anymore. I let a few non hybrids bolt for seed collecting as I find these far tastier than many of the hybrids. And they're loads cheaper