I accidentally let my big broccoli plant flower in February. I don't really go outside when temperatures dip into the 30s and 40s, so before I knew it my broccoli plant was a mess of yellow blooms and all I could do was watch from my heated living room. I knew there was no way to prevent it from blooming without braving the insanely cold temperatures and possibly slipping into a hypothermic coma...so I just let it happen.
When I finally did venture outside I noticed that the plant was alive with bees. At one point I counted over 20 bees on it going from flower to flower in a mad rush to get as much nectar as possible from the only flowering thing around.
I figured the rest of the garden was pretty much dead so the least I could do was let this flowering broccoli thrive to feed this mass of bees. It lasted for a good month before it wilted and the bees went away.
I then yanked it out and tossed it in the compost. It was definitely great while it lasted though - the bees seemed happy to have something to buzz around in this insanely cold winter. And I enjoyed watching them.