Winter Sowing Seeds in Milk Jugs
Winter Sowing Calendar:
In Gardening Zones 1-7, winter sowing works great from January-April.
If you live in warmer climates, winter sowing works great in Zones 8+ from September to February.
Winter Sowing Guide:
2. Cut the Jug:
If it's a jug, cut it in half so that you have about 4-5" bottom to fill with soil. You can leave a "hinge" by not cutting all the way around if desired, or cut it off entirely.
3. Fill with Damp Potting Soil:
It's good to mix your well-draining POTTING soil with water to get it nice and moist first (don't use topsoil or garden soil for these, it should be a loamy fast draining potting soil). Fill the container with about 4" of soil. Spritz with more water to make sure it's nice and damp before planting your seeds.
4. Plant your Seeds:
Plant your seeds sparingly, we tend to overseed these thinking that all the seeds won't sprout, but most usually do so you'll have a crowded situation if you just dump a hole bunch of seeds in like we did last season. ;)
If you do over-seed, you can gently separate seedlings in the spring when ready to transplant, so we made it work, but this year we were much more reserved in the number of seeds we planted to give each seedling some space. You can refer to the seed packet for seed spacing.
You can start cool season vegetable seeds such as lettuce, broccoli, spinach, green onion, sugar snap peas, cabbage, cilantro, oregano in January-February in your winter sowing jugs.
Winter Sowing Tomatoes and Peppers:
You can also try frost-sensitive vegetables like Pepper Seeds, Tomato Seeds, Eggplant Seeds, Basil Seeds, Cucumber Seeds, and other warm season vegetable seeds using this winter sowing method, but it is best to do so after the temperatures have warmed up about 4-8 weeks before your last expected frost. If extra cold weather well below freezing is expected, you may want to protect them by covering them with a blanket on frosty nights, or bring indoors. Also, keep in mind that some of these summer vegetables grow quite fast and need to be transplanted before they start to get root bound, especially cucumbers and tomatoes, hence another reason to start them closer to transplanting time so they don't get root bound.
Keep in mind that cool season veggies like Lettuce are much more tolerant of cool temperatures than pepper seeds and seedlings. Pepper seeds typically like 80-90˚ F temperatures to germinate and grow. Tomato seeds are a little more forgiving, as they germinate quickly and can tolerate a little more cold and still put on growth than most peppers can. We want to try starting Cold Tolerant Peppers like the Bulgarian Carrot Pepper in the winter months, they are supposed to be more cold-tolerant than most peppers so it will be a good experiment!
Learn more about how to germinate pepper seeds »
Tomatoes are fast growers, and they like to be able to stretch their roots, so if you do use Winter Sowing to start tomato seeds, make sure to transplant them as soon as their roots start hitting the bottom of the container. When you transplant them to a larger pot, make sure plant their stems deep to encourage a nice deep root system.
5. Water in the seeds to make sure the soil is damp but not soggy, make sure the containers are draining well.
Add labels (we like to put them inside, you can also use a paint marker / pen on the outside of the container - sharpies tend to fade in the sun, so use a paint pen if you have one). We have found that whatever you use it is critical to mark the bottom of the jug as an added measure as the sun can fade most inks.
Put top of the jug on (discarding lid), place outside in a sunny spot.
To close the jugs, some people use duct tape to seal jugs around the cut, but we have also just cut off the lids entirely, and cut a couple slits in the tops, then tucked them into the top into the bottom with the top of the jugs, no duct tape is needed if they're snug (they're a little harder to move however, if they aren't taped shut, but we don't move them much anyway and if we do, we just carry them from the bottom). Duct taping may also help if you have high winds and the tops keep blowing open. We've also seen people use a paperclip "hook" to keep the lids closed. Whatever works best for you!
We always think less is more.
Make sure to put your jugs outside in a sunny location!
It is important they receive sun so pay attention to long winter shadows, and put them in the sunniest place you can find.
It's ok if it snows on them!
And yes, you leave the lids OFF so they have a "chimney" to vent out the hot air on sunny days and allow for air circulation.
Be patient, it will likely longer than expected for the seeds to sprout, they will sprout in their own time with the weather warms up enough for germination. Even if they do germinate, they won't grow fast either at first during the shortest and coldest days of winter. They'll start to take off as the days get longer and warmer.
Water jugs as needed!
Keep an eye on them and use a spray bottle to water them through the holes every week to 3-4 weeks depending on your climate and the number of sunny days which dry them out faster. Water whenever the soil starts to get dry to keep the soil and seeds moist. In more humid climates you may not need any added water, while dry sunny winter climates can result is faster evaporation. The seeds will sprout in their own time, so be patient, it could be a month or more depending on the seeds, the weather, and when you start them. Once they sprout, keep watering them as needed, and as springtime approaches, you can open them up during the day to get breezes and get more hardened off.
6. Harden off and transplant seedlings as weather permits
After your winter sowed seedlings have sprouted a few real leaves, and the weather is improving in March/April/May, you can start considering transplanting the seedlings to garden beds or containers.
First, make sure to harden off the seedlings, then you can transplant cool season veggies to your garden, such as lettuce, broccoli, spinach, green onions, sugar snap peas, cabbage, cilantro, oregano. Hardening off menas to allow them to gradually get used to full sun without the filtered light from the jug top. Start with dappled shade and work up to full sun over a series of days. Winter sown seedlings are more hardy from the get-go than indoor-grown seedlings, but they also still need to get used to the strong sun rays and the breezes after being in their mini-greenhouses.
You can transplant these cool weather veggies earlier in your garden than summer vegetables as they can withstand a bit of frost. Once transplanted, you can also cover them with a frost cloth or small garden bed hoop house when extra cold weather is expected to keep them warmer – any cover is helpful during deep freezes or snowstorms. Spinach, lettuce and green onions are especially hardy and even if frozen, they may lose a few leaves, but they usually will keep growing as the spring weather warms.
WE CAN'T STRESS ENOUGH:
DON'T FORGET TO HARDEN OFF SEEDLINGS!
If you start these frost-sensitive vegetables using this Winter Sowing method, start them closer to spring – and make sure to keep the plants covered in their containers (but still with the lids removed for air circulation) and don't transplant into the garden until all chance of frost has passed.
Pepper seeds need a lot of warmth to sprout, so if Winter Sowing it would be best to start them in April/May is probably best in most colder climates. You can also bring your pepper jugs indoors and just put them out during the day on extra cold nights, or cover with a blanket at night and leave them outside. You can also cover them with row covers or old sheets work to trap heat overnight or on cold days. Generally, cover the bottles anytime the temperature outside is below about 40F.
If a long deep freeze is expected with cloudy weather (no sun), definitely move winter sowed pepper seedlings to somewhere a warm and protected until the deep freeze has past for the best success. Peppers are very sensitive to frost.
The Brunswick Cabbage above was started from seeds
using the Winter Sowing Method with milk jugs! We gently separated the seedlings and had a whole plot of beautiful cabbage heads to harvest in the summertime. We over-seeded the jug, so they were a bit hard to separate, but the seedlings transplanted well, nearly every one survived.
Winter Sowing Seed List:
Best Seeds for Winter Sowing:
We find that cool season vegetable seeds work great for extra-early sowing so that they can be transplanted into the garden earlier in the spring. These cool-weather tolerant veggies don't mind the colder weather of early spring. Native plant seeds for flowers like Liatris, Coneflowers, Goldenrod, Asters and others also work great with Winter Sowing – the cold temperatures and consistent moisture of winter sowing helps to stratify the seeds for better germination. But really, pretty much all seeds work great in winter sowing!
What seeds are not good to Winter Sow?
Not all seeds work great for Winter Sowing. For example, Zucchini, Spaghetti Squash, Summer Squash, Cucumber, Pumpkin, and Radishes are best direct seeded – as they grow quickly and won't do as well with Winter Sowing. You COULD start some of the zucchini, squashes and cucumbers in a Winter Sowing jug, but be sure to transplant them soon after they sprout so they don't have many roots yet, they do not like to have their roots disturbed, so transplanting when very small is your best chance of success. Remember, they grow quickly, so don't start them more than 2 weeks ahead of your last chance of frost before starting the seeds. Really, all of the above veggies like squashes and radishes are best direct planted in your garden as they sprout fast and grow best without being transplanted, and it saves you time and energy!