Both Pro-Mix and Fafard are readily available here (sorry morz8!!) within a few miles in any direction. I use Fafard Profesional Growers mix since it's the same formula and costs a few dollars less than Pro-Mix. I buy 2-3 compressed bales around the middle of August & store them in my garage so they're ready to use (and not frozen) when winter sowing rolls around. I do mix in some MiracleGro potting mix but only because I did it the first time I WS and go by the theory, if it ain't broke, don't fix it. I also find it absorbs water more quickly with the MG mixed in. This year I also threw in a little potting soil. I mix it all together in a large bucket before I fill my WS containers. This is a shot of my pot ghetto in June:

I did something very similar in 2003. Just around thanksgiving with our first snow, I broadcasted out the prairie seeds over a 60x15 prepared area. No mulch, no amendment and the blanket of snow was my protection from birds. Also by this time the mice/voles ect. are housed up for the winter. My seed (flowers/grasses) were individually ordered from reputable native seed suppliers...no walmart mixes just for the simple fact you usually can't find any that do not contain a few non-native noxious/invasive species...like Dames Rocket, Bachelor's Button and Baby's Breath for example; two of which are on our local monitor list and one which made it too the noxious weed list.

The other advantage to wintersowing, besides being less expensive than buying (what pathetic selection they have available) at the nursery, and also having the space to coddle seedlings all over inside--messing with supplemental lighting, etc., and that your plants will be hardier and already hardened off, is this: your plants will also be hardier through the hotter months, and more resistant to the cold at the end of season. My wintersown tomatillo survived a pretty hearty frost last year, but the indoor-start one (yes, same seed/variety) didn't make it. However, one of the drawbacks is that, for some plants, there won't be enough head start to get big enough to get some harvest. For example, if you have longer-to-ripen tomatoes, they might not be ready to go before the first frost. Also, peppers will have a later start, etc., and something that didn't occur to me until a few days ago, is that my "120-day" okra (it's not really that long to harvest since it's a continual thing) will be so far behind the 8-ball that it might be August before we get our first okra, whereas if I have indoor or nursery starts, they are usually flowering in June. This might be particularly true if your actual growing season is shorter, like Bonnie's. The other thing to remember is that not all things are suitable for true wintersowing--basil and some herbs are a little too intolerant of the cold that if they sprouted then there was a freeze, they might not make it. However, if you're starting now, I think you're good to go on just about anything from the cold-intolerant timetable. That being said, I always start some stuff inside, and try to put it outside for as much natural sun during the day as possible, then bring it in at night until the nights are warmer. I do "backup" starts for the tomatoes that I can't live without (so then, will someone please explain to me how I have over 40 starts? Oh yeah... the SWAP!), and ALL my peppers and herbs--and certainly, the cherished okra. Also, I stupidly started some cipollini onions WAY too late (but I bought the seeds, and they'll be no good next year) inside, so we'll see if those guys turn out. Of course, Trudi D will tell you that she started wintersowing as a great experiment because she was going cabin-crazy in the deep of winter and just wanted to make some mud pies in January... (My husband now wonders, since we move our tomato containers into the garage and harvest until February, if he will ever see his wife's fingernails without any dirt under them... I'm goin' with NO)

Carla, I do both direct sow and Winter Sow. I direct sow seeds if I have a huge collection of them. I Winter Sow those seeds that I don't have too many to waste in the rain or snow. I like Winter Sowing because of its ease and it does not require as much care and expense as indoor sowing. I also have a lot of success with it. I am able to grow a lot of seeds that I failed to grow indoors. Please check out the link below. It's still not too late to start. The seedlings are healthy and grow very fast and well. They cost a lot less than those seedlings from garden centers or nurseries. Have fun. Here is a link that might be useful: Winter Sowing FAQ