How to Start Garden Seeds Outside Using a Milk Jug Greenhouse
Starting flowers and vegetables from seed is both a fun and economical way to garden. Buying seeds gives you an almost limitless amount of variety to choose from, and it’s much cheaper than purchasing already-started seedlings at the nursery or flower mart.
However, if you live in a northern region with frigid winters, cold late springs and a relatively short growing season (check the USDA Plant Hardiness Zone Map for your region’s zone ratings and guidelines), frozen soil and the danger of late frosts means you may not be able to plant certain seeds, like tomatoes or impatiens, directly into your garden. Most seed packet instructions will direct you to start those seeds inside some 8-12 weeks before planting outdoors. But 8-12 weeks is a not-insubstantial amount of time, and space can be an issue. In other words, where do you keep the seeds during that period?
The cost and variety of the seed starting supplies can be daunting as well. Should you go with a seed starter kit? Or individual trays, humidity domes, and peat pellets? Grow lights? There’s also the issue of what to do with the starter materials after the seedlings have been transplanted to the garden or containers. Do you have the space to store them for the next spring’s planting?
Fortunately, it doesn’t need to be this complicated, as these types of seeds actually don’t need to be started inside. All you need is a bag of potting soil, a small outdoor space, duct tape – and plastic milk jugs! Yes, milk jugs.
Incredibly, this method works whether you start the seeds in winter or spring. I first tried this in early March 2008 with a dozen different varieties of seeds, including tomatoes and lobelia. The seeds went through Zone 4a freeze and thaw extremes ranging from -12F (-24C) to 80F (27C) – and by late-April, everything had sprouted.
What You’ll Need:
Gallon-sized milk jugs, washed, rinsed, and air dried, with the lids removed
A heavy-duty knife or scissors
Flower or vegetable seeds
A bit of outside space (patio, deck, balcony), partially sunny and sheltered from wind
Using the knife or scissors, poke 4-5 drainage holes in the bottom of the milk jug, then cut the milk jug almost in half around the middle. Leave the handle intact.
Open the milk jug and fill the bottom half with potting soil, patting down constantly, until the soil is firm but not packed and comes to within 1/2-1/4 inch of the cut line.
Sprinkle the seeds over the soil and mix into the soil with your fingers. Add more soil to top it off, if needed, and water until the soil is soaked through.
Close the milk jug and, using duct tape, tape the two halves of the milk jug back together. Label the containers with a waterproof permanent maker and place outside in a partially sunny location. (Partially sunny, because too much hot spring sun might cook the seedlings.)
If the weather is significantly and unusually dry, add water as needed. Otherwise, you can let the natural snow or rain cycle provide the necessary moisture.
When the evening temperatures reach and then consistently stay above the freezing point, start periodically checking the milk jug greenhouses for sprouts.
As the weather becomes warmer and the sprouts grow into seedlings, cut additional “air holes” into the top of the milk jugs. When the seedlings are well established, remove the duct tape and fully open the greenhouses to the elements.
Transplant the seedlings into your garden or containers as recommended for your USDA Zone. Remove and discard the duct tape, rinse out the milk jugs, and either save for the next spring’s planting or recycle.