Actually, NOW is a good time for many of them -- they'll be small plants that will go through the winter, and many kinds will grow enough to bloom next year. Now through about Labor Day.

You can also sow very late, like in November, to "winter sow" the seeds, and they will come up in the spring with the return of warmer weather.

Either method works.

denninmi-can you winter sow the seeds directly in the ground in zone 5?

I've planted lupins and icelandic poppy seeds directly in the ground (in a fairly sunny spot) in November and they bloom the next year and I think zone 5 should be fine for this. The trick the next year is learning to recognize the foliage so you don't mistake them for weeds during spring before they bloom in summer.