Grew broccoli for the first time this year. The answer is worse, chewier, stringier.

It becomes bitter.

It’s closely related to mustard, and mustard’s distinct flavor is from the seeds. So I’d assume that if you leave it long enough for the blooms to seed, they’d taste similar to mustard. Most plants tend to get bitter after they bloom, because they send all of their nutrients to the flowers. And mustard does tend to be fairly bitter.