How to Winter Sow Seeds in a Milk Jug
Get a head start on your spring garden without an elaborate indoor seed-starting setup. Former organic farmer and garden expert Logan Hailey explains how you can reuse milk jugs as mini-greenhouses for starting seeds outdoors.
Contents
It’s hard to resist sowing seeds too soon when you’ve been curled up inside all winter. If you’re eager to start your garden, you don’t have to wait for snow to melt or the ground to thaw. In fact, you don’t even have to invest in an indoor seed starting setup with lights and heat mats. Instead, consider winter sowing seeds in an upcycled milk jug container to create a mini greenhouse outdoors.
Let’s dig into the seven simple steps to starting seeds in the middle of winter by using this frugal gardening method.
What is Winter Sowing in a Milk Jug?
Winter sowing is sowing seeds in upcycled plastic containers or milk jugs to use as miniature greenhouses that you place outside in mid-winter. When the weather warms in the spring, the seeds can naturally “wake up” and germinate in the warmth of the plastic container.
Once they reach a sufficient size, you can easily transplant seedlings from the jugs into garden beds. This frugal seed-sowing method helps beginner gardeners grow seedlings without investing in an elaborate indoor seed-starting setup.
What Are the Best Containers for Winter Sowing?
Any clear or translucent, rigid container that can function as a mini-greenhouse will work. Milk jugs are considered the best container to winter sow seeds in because they’re cheap, nicely sized, widely accessible, and easy to reuse.
Even if you don’t drink milk, you can collect jugs from a local coffee shop or ask a friend to reuse their empty containers. You can also use plastic greens cartons, 2-liter plastic bottles, water jugs, planting domes, clear plastic bins, or any clear container that can be vented and drained.
7 Steps to Winter Sow Seeds in a Milk Jug
Bring your garden more in tune with nature and keep your hands busy while you wait for spring! This seed-starting technique is cheap, low-maintenance, and super easy for beginner and advanced growers alike. Very few materials are needed, and the process takes less than an hour.
Prepare Your Milk Jugs
Collect empty plastic milk jugs throughout the winter and keep them clean and dry. When you are ready to winter sow, grab some scissors or a box cutter!
To prepare the milk jug greenhouses:
- Dispose of the lids (the hole in the top acts as a vent)
- Cut the jugs in half, leaving one side in place as a “hinge”
- Ensure the bottom half is at least 4-5” deep to hold the soil
- Cut or drill drainage slits in the bottom to allow excess water to filter through
Repeat this process for every container you have. Each milk jug should have a bottom with drainage holes and a hinged top with an air hole (where the lid was).
Choose Seeds to Winter Sow
Winter sowing may seem counterintuitive to those used to starting seeds indoors in a warm, protected environment. But this process makes perfect sense when you consider nature’s way of doing things.
Most wildflowers and vegetables produce flowers in summer and mature their seed pods in late summer or fall. If allowed to drop their seeds, the next generation of plants would naturally overwinter in the soil until the warm spring weather wakes them up from dormancy.
Cold stratification mimics this natural winter tendency indoors. Many people pop their seeds into the refrigerator to “fake” a winter. But with winter sowing, they will naturally cold-stratify in their containers outdoors as they were always meant to.
Vegetable Seeds
Cool-season veggies and greens thrive with winter sowing. Surprisingly, you can also winter sow warm-season crops like pumpkins and tomatoes. If you’ve ever seen volunteer plants pop up from last year’s patch, you know these seeds have no trouble overwintering in their dormant state naturally!
- Arugula
- Beets
- Bok Choy
- Broccoli
- Cabbage
- Carrots
- Chard
- Cucumbers
- Collards
- Corn Salad (mache)
- Kale
- Lettuce
- Leeks
- Onions
- Peas
- Pumpkins
- Radish
- Scallions
- Spinach
- Tomatoes
Herbs
Many herbs grow well using this method, resulting in a stronger start to your spring herb garden. Try some of the following:
- Chamomile
- Chives
- Cilantro
- Dill
- Lavender (especially benefits from cold exposure)
- Lemon Balm
- Mint
- Oregano
- Parsley
- Rosemary
- Sage
- Tarragon
- Thyme
- Valerian
Perennial Flowers
Perennial flower seeds are ideal for this method, particularly if they are native wildflowers in your growing zone. In the wild, these flowers naturally drop their seeds in late summer or fall, and the seeds go dormant as they overwinter on the soil surface. The cold exposure can help trigger strong germination in spring.
- Artemisia
- Bachelor’s Button
- Bee Balm
- Blanket Flower
- Blazing Star (Liatris)
- Butterfly Weed
- Catmint
- Chinese Lanterns
- Chrysanthemum
- Coneflower (Echinacea)
- Coreopsis
- Creeping Thyme
- Daylily
- Delphinium
- Dianthus
- False Indigo
- Foxglove
- Globe Thistle
- Hellebore
- Milkweed
- Phlox
- Rudbeckia (Black-Eyed Susan)
- Salvia
- Shasta Daisy
- Veronica
- Yarrow
Hardy Annual Flowers
These semi-hardy and hardy annuals need frost-free weather to germinate, but they remain dormant in the milk jug planter until the weather is warm enough to trigger sprouting.
- Calendula
- California Poppy
- Celosia
- Cornflower
- Cosmos
- Forget-Me-Nots
- Larkspur
- Mexican Sunflower
- Nasturtium
- Nigella
- Petunia
- Snapdragons
- Stock
- Strawflower
- Sunflower
- Sweet Alyssum
- Sweet Peas (the flower, not the vegetable)
Add Moistened Potting Soil
Use a well-drained potting blend that is rich in compost and a drainage material like perlite or vermiculite. Pre-wet the potting mix until it is about the consistency of a wrung-out sponge. It shouldn’t be too soggy, but it shouldn’t be bone dry, either.
Fill the bottom of each milk jug about 3-4” deep with potting soil. Smooth the surface with your hand, but avoid compacting the soil. Air holes are great for baby plant roots!
Plant Seeds
Now, you can gather your seed packets and plant those seeds! Be sure to plant each species at the proper depth. As a general rule of thumb, sow seeds at a depth about twice their largest dimension or follow the recommended depth suggested on the seed packet if one is there.
If tiny seeds like lettuce or basil are buried too deep, they will have trouble germinating. It’s best to sprinkle a very fine dusting of soil over the top of these seeds.
Many wildflower seeds should only be pressed into the surface and left uncovered, especially if they require light to germinate. Larger seeds like peas and pumpkins must be sown ½” to 1” deep into the soil.
Label Containers
Skip the popsicle sticks and use a permanent marker to label the jug with the seed variety you will plant inside. Labeling in a few locations helps in case the sunlight or weather fades the marker.
Tape Jug Shut
Cover the lid of the milk jug over the bottom portion and use packing or duct tape wrapped around the center to keep the jug shut. Don’t use too much tape because you need to open this “greenhouse dome” in the spring when the weather starts to warm and the plants need more ventilation.
Placement
Put the seeded and taped jugs in the garden, exposing them to full sunshine and the elements. The seeds know when to germinate and will happily take care of themselves if they have enough moisture and light. You can leave the winter sown jugs outdoors without any protection. All you need to do is check the soil moisture every couple of weeks leading up to your expected last frost date.
When the seeds germinate, you may need to thin them to ensure they have enough space to thrive. Once they develop strong root balls, you can transplant them into garden beds, grow bags, or a larger pot.
Final Thoughts
Milk jug winter sowing is a cheap and simple way to start seeds without grow lights, heating mats, or cell trays. The method is eco-friendly because it uses upcycled containers as little greenhouses. It also allows seeds to wake up from dormancy whenever nature tells them to. Don’t forget to label your containers and ventilate them when daytime temperatures reach 50 or 60°F. You don’t want the inside of the milk jug to scorch the young plants.
