I've been observing my two broccoli plants over the past months and wondering why they are behaving so differently from each other. One of them began making yellow flowers a while ago while the other did not. Now, the non-flowerer is creating some impressive broccoli heads and the flowerer is not. So, I went to my gardener knowledge center, Google. I came across another gardener with the same problem and the comments to her post were insightful. Apparently if the weather is not just right (too hot or too cold) the broccoli plant will go into seeding mode and skip the creating edible broccoli mode. So basically, it is now useless and I can pull it out after I let the bees have a little more fun with the blossoms.
My flowering plant got so top heavy a few weeks ago that it fell over, right on top of some of my lettuce. I would have just pulled it out then if I would have known I would get no veggie from it.
All in the process of learning while gardening. That's why I do it, to learn from experience!