It is thought that seeds which follow this cycle and are outside to endure the cool evenings and warm days during the early spring form stronger plants than those that are coddled inside under lights and warm temperatures. This makes a lot of sense to me. In fact, there is a website devoted to the concept which gives suggestions and ideas about how to do this.
It appears one of the most prevalent ways to accomplish winter sowing is to use gallon milk jugs. I started saving milk jugs weeks ago, but when I was ready to start my seeds, I didn't have enough, so I went to a couple of the local coffee shops and asked for their empties. Aspen Coffee gave me a whole trash bag full of empty gallon milk jugs!
The first step was to rinse them out and cut them around the middle with an X-acto knife, leaving a small "hinge" at the bottom of the handle.
Then make drainage holes in the bottom. There are several ways to make the holes. One is to heat a nail over the stove and melt a hole in the plastic. However, I used a Dremel tool fitted with a small drill bit.
After the seeds are planted, close the jug and seal it with duct tape, like this.
Label the jugs with a felt-tip marker and set them in a sheltered place where they will get some of the winter sun.
Once the plants are up, you will have to keep a close eye on the jugs to make sure they don't dry out. Also, when the days are consistently warm and sunny, you will need to open the jugs up to keep the little plants from cooking. There will be a period of several weeks where you may need to open them during the day and close them again on frosty nights. You should not have to re-tape them, but just use a short piece of tape to close the jugs for the night.
After thoughts..... In retrospect, I believe I cut some of my jugs too shallow. They need to be deep enough to put 2-3 inches of soil in. Also, I ran into problems taping the jugs shut because of the indention that many jugs have in the side.
A solution to both of these issues is to cut the jugs at the top, like this.
When cut this way, the jug is deep enough so you can put in as much soil as you like and it also avoids the problem with taping over the indentation in the side. It also uses less duct tape.
It will be interesting to see how this works. Judging from the one jug of annuals that are already up, I know I put too many seeds in the jugs. I'm sure I will have to thin the plants and only keep the number I need.
It is still not too late to give this a try. All the seeds I have planted so far are flowers of various sorts, perennial and annual. But, I want to try starting a few tomatoes and peppers with this method and compare them with the ones we normally start in the basement under lights.
My biggest problem is going to be where to plant all these flowers, if they all come up!