That is what I use, and it works for me.

Thank you ontnative! I got a couple small bags of other stuff (compost, potting mix,& topsoil). I am going to try different combinations & see what works best. This will be my first time trying winter sowing & I'm just getting everything pulled together.

In my climate with rain 9 months of the year and dry summers drainage in containers is important. Topsoil & compost may have windblown weed seeds or more.

You might want to stick with bagged potting soil or the seed starting mix.

Growsy, Corrine is right. Compost and topsoil have been tried in containers, both for winter sowing and otherwise, and they just aren't suitable for container mediums. They will compact, give you headaches with the drainage, not allow for good root development.

A soilless product formulated for use in enclosed space/pots will give you the best results. I'm not even crazy about the seed starting mixes (prefer potting soil) for no-attention outside sowing. Seed starting mixes are very lightweight and you may have to watch the water needs, also are nutritionally inert so seedlings may require at least a weak fertilizer before you have a chance to plant out. A water soluble formula that you've mixed and applied as a liquid is safest for seedlings generally, one you can mix at a reduced strength than the package instructions indicate.

Seeds have all the nutrition they need right inside their little bods for getting up and running. No need for anything in the soil other than peat/perlite/vermiculite (soiless mix). They will take up nutrients from the soil once they are transplanted in their permanent homes.

That's true, they don't need additional fertilizer to germinate, they have all the energy they need stored in one tight little package - always a miracle :)

While some here will be planting out into their gardens at stage of first true leaves, not all of us can or depending on the type of plant, would want to. That's when those seeds if started in a seed starting medium rather than a general container mix will begin to need some attention, when true leaves are formed.

My soil isn't perfect, its clay base not always friendliest to tiniest root systems and I like for plants to have a little longer head start and more developed root system before planting them out. I have to allow a margin for timing spading too, I cannot always dig in earliest spring, beds too saturated from our winter wet and spading then too hard on the soil structure.

Perennials, trees, shrubs started in a container of potting soil with enough depth are fine left as is, in a seed starting medium they would need a dilute fertilzer solution regularly, or would need to be potted up into individual pots, not steps we may need to otherwise take.

Thank you all for the input. I have been reading a lot about winter sowing & it seems like there are a lot of variations. I am in a very warm area, so I should be able to plant out most things with their first set of true leaves. In fact, we're expected to have temps in the 70's next week, although it will cool off again. That is one of the factors that has made me wonder if this will work for me. I'm going to go ahead & give it a try, though. Sounds like most people use the potting mix, & some the seed starting, and fewer use the other options. I do want to avoid re-potting as much as possible - I figure one of the best things about winter sowing is the time savings over starting indoors & potting in individual containers. Thank you again for all your help.