Winter Sowing

Winter sowing is when you plant seeds outside in the winter. This method uses mini greenhouses to get a jump start on spring. Some seeds germinate better when they go through the freezing/thawing cycles of winter/early spring. Read on to learn more about how we planted seeds in February in Michigan!

The first thing you need is milk jugs, 2-liter bottles, or any kind of clear container. We used milk jugs since we go through several gallons a week. While collecting up your milk jugs make sure they are clean and discard the lid since you won’t need it anyway. The white jugs will not work, they need to be the translucent ones that let light through. Using a knife cut the jug in half, leaving a section by the handle intact.

Then take a drill and drill holes in the bottom of the jug for drainage.

Next is the fun part! We don’t use any special potting soil, just what we have left over from last year. You need to mix your potting soil with some water to make it damp. Then put 3-4” of the soil into the bottom of the milk jugs. Firming the soil lightly.

Next comes planting the seeds! If you search online you can find lots of seeds that will work well for winter sowing. If you look on a seed packet and it says anything about “chilling before planting” or “plant before last frost” it would be a good option for winter sowing. Any plant that reseeds itself is also a good candidate. So far this year we planted: bachelor buttons, bupleurum, coneflowers, delphinium, euphorbia, larkspur, love-in-a-mist, and orach. There are a couple different ways to plant your seeds. Most of ours we do just 5 spots with a couple of seeds in each (one in each corner and one in the middle). This makes it easier to separate the seedlings when it comes time to transplant. This year, we also did a couple where we just scattered the seeds on the top. They were old seeds so I expect to have a lower germination rate and just thought I’d try it. This way, I should get more plants in one milk jug.

After planting your seeds, you want to make sure you label your jugs. I just write on the outside but I really should put a label on the inside too. Then tape the jugs back together.

Then you simply sit the jugs outside! I used a shovel to dig through the snow bank where I wanted mine. You want to put them in a sunny spot that is protected from wind so they don’t blow away. Just make sure that you don’t sit them under an eve where water will run off into the jugs. Leaving the lid off the jug provides the jug with ventilation and also allows for snow and rain to enter to keep the soil moist. Once it starts really warming up (especially on days that the sun is shining) you will want to check on your jugs and will need to open the top half to ensure they don’t get too hot. And then you can close it back up at night if the temps get too low. You will also want to keep on eye on your milk jugs and make sure they don’t dry out too much. The milk jugs mimic a little greenhouse to accelerate germination, but because the seedlings are outside they are hardier that the ones grown in an actual greenhouse.

Once the weather starts to warm up, you can also use the same process for heat loving flowers and vegetables! You can therefore get your seeds started earlier than you could by just planting them in the ground without needing a greenhouse or any other equipment to get started! Just some seeds and milk jugs! I hope this helps. Let me know if you have any questions and I will do my best to answer them!