How to turn a milk jug into a mini greenhouse

By Emilie Grace Yochim

When winter creeps in with her cold, frosty air, and gloomy, shorter days, most gardeners can only think about one thing: next year’s flower garden. Well, at least, that’s what runs through my mind. How can I keep myself busy with my garden over the dreary days of winter? Two words: winter sowing.

Winter sowing is a fun, cost effective way to prepare for next summer’s native garden. Defined, winter sowing is a way to start seeds outdoors during the winter months. It is particularly useful for any seeds that require a period of cold, moist stratification to break dormancy and germinate. Another advantage of winter sowing is that you end up with plants that are hardier, and acclimated to the temperature swings. Also, you don’t need to start seeds indoors using fancy grow lights or an expensive greenhouse! 

When to start

When to start? Most winter sowers begin their project on the winter solstice. Typically, you will start with your seeds that need the longest period of time to break dormancy. Those would be the seeds that need 60 to ­120 days of cold, moist stratification. You can winter sow as late as March using seeds that need less time or seeds that need no special treatment. 

What you need

What do I need to winter sow? Well, seeds would be at the top of the list! What “new to me” native plants and grasses would I like to add? What areas need more fillers to support the other plants I already have? Which plants did the pollinators love that I want to increase in number to support them? These are all questions you can ask yourself as you decide on seeds to grow.

Where can I get native seeds to winter sow? Some reliable sources to purchase native seeds include Roundstone Native Seed Company and Prairie Moon Nursery. You can also find native seed swaps in several groups on Facebook in Kentucky, including mine Pollinators, Poof Heads & Native Plants in Kentucky, where you can get seeds for free or a minimal fee to cover shipping costs. 

I have my seeds, now what? The following materials are what you’ll need on hand:

  • Gallon milk jugs: The clear ones work best; recycle the caps as they aren’t needed; you can also use such things as two-liter soda bottles and rotisserie chicken containers.
  • Potting soil: I tend to use Miracle Gro Potting Mix. Use whatever brand you prefer, but don’t use any that are labeled “moisture control.”
  • Duct tape: For sealing jugs.
  • Sharpie marker: You’ll want to identify the seeds in each jug. You could also place a plant marker on the inside of your jug.
  • Box cutter: For cutting your jug.
  • Drill, hot glue gun, or anything sharp you can safely use to make drainage holes in your jug.

The process

With all your materials gathered, you’re ready to start:

  1. Using a drill, hot glue gun, or something sharp, make 6 to 8 drainage holes in the bottom of a milk jug. I go around the lower sides of the jug.
  2. Use your box cutter to slice your jug from side to side, leaving the handle attached, about halfway down. Don’t cut the entire top portion of the jug; leave a few inches intact. The top will act as a lid that you can open and close.
  3. Add 4 inches, or so, of wet potting soil into the bottom of the jug. 
  4. Sow seeds according to directions. For example, you’ll sow some seeds on the surface and plant others at specific depths.
  5. Close the lid, and tape the jug back together using duct tape.
  6. Label the jug with your Sharpie. 
This photo shows the different stages of a milk jug being transformed into a mini greenhouse for propagating seeds.

Once your jugs are filled and taped shut, place your jugs in an area with sun. Moisture (rain and snow) will enter through the top creating condensation (aka your greenhouse). You can spray the inside if things start to dry out. 

This photo shows numerous milk jugs heeled in for winter.

Now, sit back and let nature take its course! Once spring is here, and temperatures warm up, open your jugs. Be sure to water as needed. If we get a frost or freeze, put the lids back down or cover the jugs with a blanket. 

This photo shows a couple of milk jugs with small germinating plants.

Once seedlings are ready to transplant in late spring, take them out of their containers, separate them in “hunks,” and plant them directly in the ground. If they’re small and still need more growing time, use the same method, but place them in pots to grow until they’re large enough to put in the ground. If your seedlings are large enough to separate, I’ll use Asclepias incarnata (Rose milkweed) as example, then by all means separate them instead of using the “hunk” method. 

Winter sowing helps us look forward to spring with the anticipation of new life growing in our containers and the pollinators that will enjoy them in the summer. It is a highly addictive project; you have been warned! I winter sowed over 130 containers last year, and I can say I likely won’t do as many this year, but then my plant pals who know me will just laugh and say, “yeah right.”

And, as always, please remember to support your local native plant growers. We need them to be successful in making native plants more accessible to the public and retailers!

Editors’ Note: You can follow Emilie’s backyard restoration by reading Replacing Invasives With Natives Is A Work Of Love.


Emilie Grace Yochim

Emilie Grace Yochim is a homeschooling mom to two teens and has been married to Philip for 20 years. Since 2019, Emilie has developed a slight obsession with pollinators, poof heads (bantam Satin and Silkie chickens), and native plants.

She enjoys educating others about planting natives and identifying pollinators by sharing pictures and information about the native plants, chickens, and wildlife in her yard. She also enjoys making terrible memes and puns that she finds hilarious.