If you live significantly north of the Mason Dixon line and trudge through cold white winters, if the ground freezes for more than 2 months and you can see your breath as you shovel out your driveway, fall seeding may be for you. Because of the shorter growing season, you will get a head start on spring and should experience floral bombardment of your yard up to a month sooner than your traditionalist neighbors who are spring planting.
Timing Wild Flower Plantings
An important caveat when sowing seeds for fall planting, is to be sure that it's cold enough so the seeds don't pop up before winter and fizzle come spring. A few seeds also require cold stratification, they need to experience their winter dormancy before springing up once the warm weather returns.
Ground temperatures should have cooled enough, where you can still punch a spade into the ground without encountering ice hardened soil, but there is no chance of the seed germinating prematurely. Ground temperatures for fall planting should be below 45 degrees but above freezing. Try and get them in the ground just after the first hard frost, NOT snow, just frost.
Prep your soil by removing weeds and pre existing growth and debris. Get rid of any weeds and grasses, roots and all, to make plenty of room wildflowers to thrive. Turning the soil is also advisable..
Sowing Wild Flower Seeds
Scatter your seeds according to the package directions. Do not bury or cover wildflower seeds with soil. Just a light watering to affix them in place is all that is needed. Yes - you'll loose some to the wind and runoff over winter, which is exactly why you'll plant more than you need.
When scattering wildflower seed over larger areas by hand, a nifty trick is to add dry sand to your seeds first. It's important that the sand be dry otherwise it will form clumps with your seed making it difficult to spread. The light colored sand will allow you to see exactly where your seed has landed, which will enable you to spot out bare spots and areas of excess application.
For the best chance of success, each particular plant's requirements should be researched..
If you live in a warmer climate See: Fall Planting Wildflower Seed in Warm Climates