A few of my "new" rhubarb plants sent up flower stalks this week. As I always do, I promptly cut them off so the plants will not spend any energy on flowering and making seed. In most years, this is so the plants will use that energy to keep producing and I can harvest more rhubarb. This year, I'd rather that energy go into reestablishing a good root system so next year I can harvest even more rhubarb!
Once the flower starts to emerge, I remove the flower by cutting it off with a sharp knife. I try to get as close to the ground as possible, as there are multiple levels to the blossom (as you can kind of see in this photo of the early stages of blooming) and I want to make sure to get it all.
As I've mentioned before, saving rhubarb seed isn't highly recommended if you want to increase your rhubarb patch, as the seeds do not consistently produce true to type. Every time I see that warning somewhere, I'm always intrigued by it. There's a part of me that's very tempted to let a flower go to seed one year, just to see what I would get, but there's a larger part of me that would much rather have more rhubarb to play with in the kitchen.