2 feet would be OK for the plants eventually. But that doesn't mean you sow the seed 2 ft apart. It would be better to sow the seed in small containers and plant them out when they are more robust. They aren't annuals to be sown in situ.

I went ahead and planted them before you posted, around 6 inches apart. I think most people around here sow them in the ground, and then once they flower, they reseed.