When I woke up on Monday morning, it was -9 degrees Fahrenheit.
And guess what? I planted seeds on Sunday. In the middle of the winter. No, we don’t have a heated greenhouse and no, I’m not growing the seeds indoors with grow lights.
Instead, I’m using a seed starting method called “Winter Sowing”.
What is Winter Sowing?
Winter Sowing is a method of starting seeds in the winter that does not involve a greenhouse, heat mats or grow lights. This is a fantastic method for people who are tight on space and don’t have room to start seeds indoors.
Winter Sowing is just like it sounds - sowing seeds in the winter! As a general rule, you can begin Winter Sowing around the Winter Solstice (Dec 21) up until early March, depending on where you live.
Here is the basic concept:
1. Choose seeds from plants that are “cold hardy” (I’ll provide a list below).
2. Find a plastic container, such as milk jugs, soda bottles, lettuce “clamshell” containers, vinegar jugs, deep foil pans with clear lids, etc. Tall containers will need to be cut into 2 pieces, so you can access the bottom.
3. Poke drainage holes in the bottom of the container.
4. Fill the container with potting soil and sprinkle seeds on the potting soil.
5. Put the lid/top back on and secure with duct tape. Make sure there are vents for air to escape and rain/snow to enter.
6. Place the containers in your backyard… and wait until spring!
Why Winter Sow?
Depending on where you live, cold hardy annuals are planted either in the fall (climates with mild winters) or the spring (climates with harsh winters).
Hardy annuals best grown as spring or fall flowers. They do NOT like heat and start to decline and die when temperatures rise in the summer.
In my climate, it’s too cold to plant hardy annuals in the fall. They would simply freeze to death.
If I wait until spring to plant the seeds, there isn’t enough time for the plants to grow and bloom before the heat of summer is upon them! Here in Michigan, it’s not unusual for the weather to fluctuate 60 degrees in a matter of weeks (or days!).
By Winter Sowing the hardy annuals, it means I have sturdy seedlings ready to go in the ground as soon as the soil has thawed… which means I can get the plants to bloom before the sweltering heat of summer
“Cold Hardy” Plants
Not all flowers are a good candidate for Winter Sowing.
Be sure to look for clues on the seed pack, words like:
"direct sown as soon as the soil can be worked",
"direct sow in early spring"
"chill seeds before sowing"
"can withstand frost"
Here is a list of “cold hardy annuals” that are good candidates for Winter Sowing. This list is by no means exhaustive!
Ammi (Queen Anne’s Lace)
Bells of Ireland
Dara (Chocolate Lace Flower)
Monarda Lambada ( Bee Balm)
Scabiosa (Pincushion Flower)
Sweet William (Dianthus)
Keys to Success
Basically, the containers are “mini-greenhouses” that will provide your seeds with the right conditions for germination.
There are a few keys to success here:
Drainage holes in the bottom
Clear or opaque plastic that allows light to enter
Vented top/lid to allow hot air to escape and allow rain/snow inside. On a sunny day, your “greenhouses” will heat up quickly. Overheating/lack of adequate venting is a threat to the seeds. Use a knife to poke holes or cut out vents. If using milk jugs, vinegar jugs, soda bottles, etc., simply remove the cap.
Adequate potting soil to retain moisture. You’ll need about 3-4” of soil in each container.
Preparing for Winter Sowing
Here is what you need to get started:
Cold hardy annual seeds
Winter Sowing Containers (milk jugs, vinegar jugs, soda bottles, salad clamshell containers, etc.)
Scissors or X-acto Knife
Screwdriver or nail for poking holes in bottom
Sharpie marker or labeling marker
Labels (Popsicle sticks, plastic plant markers, etc.)
Here is how to prepare a milk jug Winter Sowing Container:
1. Poke holes in the bottom of the jug for drainage.
2. Draw a horizontal line on milk jug, about two inches below the handle. Start cutting on the line with scissors, leaving a small section intact, so the two halves are still attached, but you can open up the jug.
3. Fill the bottom half of the jug with 3-4 inches of damp potting soil. Gently tamp it in place.
4. Sprinkle your cold hardy seeds on top of the potting soil. For small seeds, simply press the seeds into the potting soil to ensure good contact. For larger seeds (like sweet peas), sprinkle some additional soil on top of the seeds and press gently.
5. Put the two halves of the milk jug back together and duct tape the halves in place.
6. REMOVE THE CAP from the milk jug. This is the vent that allows hot air to escape and rain/snow to enter.
Use the same method for others jugs/bottles. For clam shell containers (pictured below), simply poke drainage holes in the bottom and cut vents in the lid.
Put Those Babies Outside!
Once you’ve planted your seeds in your Winter Sowing containers, now comes the easy part!
1. Place the milk jug outside in a place sheltered from the wind (so the jug doesn’t blow away) that receives sunlight.
2. Avoid placing the containers next to the house or under eaves, where rain could pour down and damage or flood the containers.
3. Check on your containers periodically. You want to make sure the containers do not dry out. If the soil is dry, drip a bit of water in the container or heap some snow on it.
4. Waiting is the hardest part! You may think your experiment has failed, but trust that those seedlings will emerge at just the right time. The constant “freeze/thaw” activity helps the seed casing to break down and allows the seed to germinate. You may find seedlings popping up around the same time you notice tulips and daffodils coming to life.
5. As the seedlings grow and temperatures rise, you may need to add more ventilation. Frying your seedlings is the biggest threat at this point. They need to stay cool. Those mini greenhouses get hot!
5. Once your seedlings are sturdy and have 2-3 sets of leaves, AND your soil is thawed enough to work with, you can begin transplanting your babies out into the big wide world! By this point, they should be properly “hardened off” (acclimated to outdoor conditions) and ready to go!
After a long wait… one day you’ll check your containers and see this!!!
Hope this was helpful! Happy Winter Sowing!