Thank you!

To get them to grow more quickly, soak them in warm water overnight (not more than 24 hours or they could rot). It gives them a few day jumpstart. Ok if the water cools, they just germinate best at 70 to 80 degrees so that's the best water temp. Fine Gardening article on jump starting seeds.

My first killing freeze is about October 20 (it has been running later the last few years -- climate change ?) and July 4th is a good cutoff date for me. So you should have time to grow them, make any crosses you wish, and save seeds to use next year.

Just remember to sprinkle your seedbeds daily until the zinnias emerge, which, depending on soil temperature, should be in 2 to 6 days.

I see no reason why you can't start your seeds. When ours are finished, your's will be going strong.

I've used clear plastic cups, ventilated, over some of my various seeds to speed up germination. Works great.

Finished? I can't imagine a growing season luxuriously long enough that the zinnias would ever be done! Winter already feels too close and it's not even July! Thanks for the tips everyone. I feel very encouraged!

Not finished :-) For cut flower growers, Johnny's Seed (good company :-) ) recommends sowing zinnias every two weeks throughout the growing season (along with other flowers good for succession growing). Works for folks who like cut flower gardens as well. http://www.johnnyseeds.com/growers-library/flowers/succession-planting-interval-chart-flowers.html