Mojorisin,
The info I have on S. pratensis doesn't mention anything about it reblooming, just that the bloom time should be about 3 to 4 weeks long. May as well try it and find out.
You can also try dead heading most of the spikes but leave a couple so you can collect the seeds.
Adam

Found a little more info that says you may get a second bloom around the end of summer if you deadhead it. The second bloom won't be as showy as the first though and there's no guarantee that it will do it every time.

I think it could bloom almost continuously in a mild climate. Dead-heading would help. Mine bloom on and off all year, including winter, which makes it a useful plant here. The heat here limits it's blooming the most during summer.