"Wintersowing" is a relatively new thing, as far as gardening goes. I first heard the term about 15 years ago, and that is new for gardening terms. It refers to someone planting seeds in containers and putting them outside so they get the freezing winter temps they need to germinate, but are up off the ground and enclosed. These wintersowed containers will warm up and thaw faster in the spring than the ground and the seeds will germinate much sooner.
You could plant these same seeds in the ground in the fall and get the same, eventual result, but wintersowing is faster. It also gives gardeners a chance to plant and garden in the middle of the winter.
Wintersowing is better done in deeper containers. The more shallow ones, as in the top picture from a few years ago, dry out too fast in the spring. Plastic pop and clear plastic juice bottles work well.
Here is one I did today. This is echinacea 'Double Decker'.
I drilled a few holes in the bottom center and cut more around the outer edge with a knife. Then I cut it almost in half, just enough that I could lift the lid to fill and plant but not enough to take the lid off completely. I want it as securely attached as possible outside.
I filled it with storebought potting soil, since our ground is frozen solid, and planted the seeds. Echinacea seeds need a winter to germinate and they also need a little sunlight, so they get covered very little, if at all.
I stuck in a label and put it on my south facing deck with a block of ice behind it to hold it in place during winter storms. I don't have many of these seeds and would be quite frustrated should it blow over and be destroyed. I planted about half of the echinacea 'Double Decker' seeds that I have, saving a few in case these don't germinate. (It's a foolish gardener who plants all of his seed!)
I have a few more seeds to wintersow this year. This is just the first one. I'm looking forward to these special echinacea seeds for the flowerbed. As far as the herb uses go, it doesn't matter which one I have since they all have the same properties. I have single purple ones and the 'White Swan'. These flowers look like this:
Almost anything that needs a winter to germinate can be wintersowed. I plan to do a lot more this month, if I have the time.