It is the blooms that get pollinated not the seeds. The seeds develop after the blooms are pollinated. No hand pollination is required since it self pollinates. However broccolini is a hybrid, a cross to begin with so reproduction from seed will be affected accordingly. Plus if growing other members of the same family it will cross-pollinate with them too.

Dave

New, I've attached a link to an old but interesting thread about broccolini that might be useful.

Click here for broccolini thread

Thanks rhizo_1! I read that thread and that was how I found Sakata and they pointed me to several sites that I could get broccolini seeds from. I was just wondering if there's a way to make sure they go to seed, otherwise I'll have keep rebuying seeds.

As Dave notes above, as they are a hybrid, if they go to seed you will likely not get broccolini so if you really love it, you should probably just plan on buying seeds. If you are averse to purchasing seeds, you can try other things in the family to see how they fare for you such as sprouting broccoli, Chinese broccoli, etc.