Seedlings that are planted inside are two inches apart. When they are moved outside in the spring, they are planted 18 inches apart. This gives them plenty of room for 4-5 years in my Zone 5b garden.

Edward

I guess I'm pretty close as I only plant seedlings about 6- 8 inches apart when they went in the garden bed. I figured some may not make it here once we get through our winter. Once they bloom, I'll move them out to another bed just for seedlings. Like Edward, I will plant them further apart.
I believe most of the crosses from the seeds I started indoors this past winter are TETS.

Julia

My seedlings are planted between 8" and 12" apart. That is sufficient room for them for a year. Many of the dips bloomed throughout the following summer after being transplanted in October, even when they grew enough to appear crowded. We thinned them out later to leave 24" between plants. The diploids are very vigorous plants, so they are much larger and faster-growing than the tets. We did not need to move any of the tet seedlings the first year, since they do not increase like the dips.

Nancy

Thanks guys,
I will need much more space if I do that Edward although it makes sense.
Julia.
I will see what survives the winter and maybe I won't have to thin so much either. Mine are about 6" apart in the rows but I have rows also 6" apart. They looked good when I put them in but I never imagined how much they would grow.
Nancy
Did you put them in the garden in the spring 8 to 12 inches apart and then move them in October? I had several try to bloom in Sept after just being started indoors in Feb and then put in the garden in late May. It is interesting about the dips. I wasn't expecting clumps at all but they have really spread. I am wondering if they will be slower to bloom because that have many little fans as apposed to the tets which have 1 big one.

I am not too worried they won't bloom if I leave them next summer - think of how close the fans in a clump are - just that I won't be able to sort them out!