How to winter sow native plant seeds in a milk jug
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Kathi Knope
Christian County Master Gardener
Did you know that most of your native plants need cold stratification to germinate. Cold stratification is a period of moist cold needed to germinate. Do your research on how long your seeds need to germinate then plant according to directions. Here are directions you will need for milk jug winter sowing.
Materials needed are:
Clean gallon milk jugs with the lid off. Need to be clear enough for sunlight to get through.
Paint pen (you can order them online.) You will need a paint pen because the jugs will be outside and permanent markers will not last in outside conditions; or you could use recycled blinds with pencil for inside the jug.
Potting mix like Miracle Gro, the yellow label {not the moisture control because it has polymer crystals to retain moisture}, or some other good quality medium that will allow for good drainage.
Scissors or box cutters.
Drill and a block of wood.
5-gal or other container to mix water and soil.
Pipe cleaners/twist ties or poly tape. You can get the tape at a local hardware store. Tape is better.
Hot glue gun without the glue sticks.
Hole punch.
Seeds to plant.
Instructions on how to Winter Sow using milk jugs:
Use a ruler and measure at least 4 inches from bottom of milk jug. Wrap string or a big rubber band to use as a guide. Using a black marker mark a line around the jug to guide you cutting the jug.
Partially cut around the milk jug leaving the handle section for a hinge. Cut high enough to insert 4 inches of potting soil.
Two holes can be drilled, or hole punched in front if opting for pipe cleaners.
Add holes to the bottom of the milk jug for drainage using a drill or hot glue gun. I used a hot glue gun and made 4 holes. There is no set number, but you do not want the jug to hold excess water.
Pour some potting mix into a 5-gallon bucket and moisten slightly. It should be wet enough to hold together but not dripping wet. Fill the jug with 4 inches of potting mix, pressing down lightly.
Label the jug on the lower portion with the paint pen and add a label inside the jug. Include the date so you know when the expected germination date will be. Plant the seeds inside as directed on the package, pressing slightly into the soil.
Close the jug using pipe cleaners or poly tape. Leave the cap off to allow the exchange of air and moisture like a miniature greenhouse.
Water lightly and place the finished jug in a sunny place with some protection from the wind. This may mean tying twine around the handles to tie them together and tie them to a fence or post.
As temperatures warm in the spring, check the moisture levels periodically. They may need supplemental watering if there is not enough rain or snow to keep the soil moist. Place them in a tray with holes in it to stay constantly moist.
Jugs can be opened in the day and closed at night to protect the seedlings from freezing the tops of the plants.
Put the jugs up on something so the slugs will not get in them, like a deck.
When plants are consistently above freezing you can cut off the top of the jugs and grow until ready for transplant.
Transplanting can be done early on by separating plants into their own cells or pots when the first true leaves appear, or in clumps out of the jug.
References:
University of Illinois Extension — Seeds stratification: What seeds require cold treatment, January 27, 2022
Milkweed4monarchs.org — How to start milkweed seeds in milk jugs, February 8, 2021
University of Indiana Northwest, IUN on YouTube — Title: IUN Community Garden Winter Sowing 2020
Wild Ones: Native Plants
Illinois Native Plant Society
