I'm impressed as well. Honestly, I don't know what is optimum, this is my first time growing anything.
I started those in a square foot garden raised bed. It's total space is 4'x 4'. The cauliflower plants were planted in the nearest left square. As you can see they've grown huge and spread out. I didn't know what to expect when I planted anything, so I didn't thin anything out. When the cauliflower were looking seriously overpopulated, I transplanted 3-4 of them over to a larger 4'x8' bed(surprisingly no transplant shock).
In the first pic, you can see they've expanded out to almost the full 4' across, they have taken about 2' wide as well, maybe a little more. I think I've only seen 3 heads out of 6-7 plants. They've had a little rough season, we had temps in the triple digits back in June for a couple weeks and I believe that hindered growth and production.
I can't wait to pull these other heads, soak them and cook & eat them.
I've learned from this that cauliflower here does extremely well with all day sun(making sure to tie the leaves around the heads to keep them from yellowing). The plants grow big and fast, although I waited what felt like a long time for butttons to start growing into heads. I've learned they need space, more than the space I gave them. Good thing the lettuces, peas and spinach in the squares next to it were finished for their seasons.
It was an awesome experience growing what I did this year. I'm looking forward to doing it again and continuing to learn so that I can know what I can plant through our Chicagoland winters.