I'm not an expert in what you're trying to do, but I do know that seeds have temperature profiles that vary by species. Ever notice that crab grass germinates towards the height of summer? If its too warm, peas won't germinate. Of course this isn't what you're planting. There's usually a range of acceptable temps however, I've never seen a listing for flowers that shows the range for a species. I'd try the seed outdoors, but make sure you're keeping a close eye on moisture, because the higher temps are going to dry the soil out faster. You may want to (if you have the space) to try some in doors under lights where your temperatures may be more moderate, and then acclimate them to the outside. One other thing. Some of the annuals (and some of our 'annuals' are actually perennials from warmer areas that we grow as annuals), may be sensitive to the daylength, and if the daylength is decreasing, they may not flower. Again, I don't know which annuals may or may not have this sensitivity.

Hi Scarleta, I will have lots of seeds when mine dry out. email me and I will get some to you. Maybe we can trade some too. What colors are yours? Make sure you till your bed good before you sow too. Here's a good page about growing them that I found helpful. Here is a link that might be useful: Growing Poppies

The best time to direct sow warm season grasses such as blue grama is spring. You can sow a warm season grass in summer if you are able to keep them well watered and its not too hot where you are. This is a fast growing grass that establishes quickly and easily from seed. it is best to sow the cool season grasses in fall. The Prairie dropseed needs cold stratification and is very slow going from seed. Its best to purchase plants unless you want to wait a few years for mature plants. Santa Rosa Gardens sells plugs for very reasonable, especially if you wait for their spring or fall clearance sales, although they seem to be out of it currently. Big bluestem is another one that takes quite a while to establish from seed as it spends the first year or two putting down deep roots. You didn't mention one of the most beautiful and best warm season prairie grasses of all. Sideoats Grama. It is fairly fast to establish and forms seedheads rather early so its gorgeous all summer, fall and winter. Pictures do not do it justice, a mature plant is very stiff, impressive and upright and it can get quite large. The seeds germinate in early spring and it establishes fairly fast. Another good one that adds hazy purple color contrast and light effects is purple three awn grass. Its a fine bladed cool season grass that blooms purple fading to beige all spring through summer. Comes up very easily and grows fast.

Scarlet sage (Salvia Coccinea) should still bloom from seed by fall, they germinate quickly, but take some time to get going on clay. They're not 100% perennial in zone 8a, but a lot can eventually return depending on mulch/weather and they do self seed well. They bloom from now until frost, but best show for us has been in early fall. Your spot sounds good because they seem to appreciate a little shade. We've been happy using them as a temporary ground cover in the open spots while the shrubs grown in. Here is a link that might be useful: Salvia coccinea at wildflower.org