Even though it’s a method that’s been around for years, winter sowing has recently drawn lots of attention as an easy and frugal way to start strong seedlings outdoors much earlier than you’d normally be able to in the Midwest. There are lots of different ways to do this, and it’s honestly hard to go wrong.
To start winter sowing, you’ll want a plastic container ideally at least 8-10 inches tall. Empty milk and water jugs and rotisserie chicken containers are ideal. Most commonly, you’ll see milk jugs. Start by rinsing the jug out well, and throw the top away. Flip the jug upside down and use a knife or a drill to add four holes to allow water to drain.
Using your knife or a pair of scissors, cut the jug all the way around, leaving the handle attached as a hinge.
Once you’ve done that, you’ll be able to flip the top of the jug open like a lid. Using a sharpie, write the name of the seed on the inside and outside of the top of the jug. Add about four inches of regular potting soil (NOT garden soil), plant your seeds, and cover them lightly. Moisten the soil so that the seeds don’t blow around, and flip the lid back onto the jug. Using a piece of duct tape, attach the top and the bottom to create a mini greenhouse.
Put your jug outside in the sun, and leave it for the rest of the winter. The hole at the top will allow snow and rain to keep your soil moist, and the seeds will germinate when they would naturally outside. Because the seedlings are exposed to cold and the wind for their entire lives, they tend to be far hardier than seeds started indoors or at a nursery, and you won’t need to harden them off. Eventually your seedlings will be several inches tall, and you’ll be able to plant them. You can choose to either tease the roots apart and plant them one at a time, or you can cut the soil and seedlings into chunks and plant them in hunks.
Lots of people wonder when it’s too late to winter sow for the year. A good general rule of thumb is that if you still need a jacket or a sweatshirt at night, you still have time!