Winter Sowing in Zones 5 and 6 – It’s Life Changing

What is Winter Sowing

Winter sowing is a low cost method of seed starting, traditionally in milk jugs, that mimics nature, and provides the conditions necessary for seeds to germinate. The main advantage to winter sowing over starting seeds inside, is minimal care of seedlings. It is the best way to start seeds in the winter.

Other important advantages are:

  • No need to purchase lights
  • No need to purchase shelving
  • No need to find room inside your home
  • No need for hardening off of plants
  • No need to put seeds in the Frig or freezer for stratification
  • Growth of plant is generally more robust
  • Saves time
  • Start seeds earlier in the year
  • Less stress
  • No issues with damping off

Winter sowing differs from snow sowing in that you are providing a little mini greenhouse for the seeds instead of just tossing them on top of the snow (which is a great way to sow grass seed).

You can watch my video on winter sowing on YouTube.

When to Start Winter Sowing

Winter Sowing can be started anytime after the Winter Solstice, which is December 21st or 22nd in the United States. I start in January with any perennial seeds that need a cold period to start the germination process. (This is called stratification.) Check your seed packet for how long this time period needs to be.

Over the next few months, I’ll start annuals making sure I get them done in time according to the package directions before my last frost. (I like to use this map to get a clearer image of my area for frost.) 

The last frost date for my zone 6a is early to mid-May. If the seed packet says sow 4-6 weeks before the last frost, I will try to sow those seeds by the 3rd or 4th week in March so I can plant them out in the garden as soon as they are ready. (Traditionally, we are usually frost free around Mother’s Day.)

My garden is actually on the border of zones 5b and 6a. When we get close to May, I start paying particular attention to the weather because that last frost changes from year to year. This is most important when transplanting the seedlings from their containers or even if you just have the tops off of the containers.

What Are The Best Seeds For Winter Sowing

All seeds can be winter sown except for tropical plants because a freeze will kill the seeds.

If you are still concerned, here are a few hints:

  • Any seed that self-sows is the perfect candidate as it will lay dormant through winter and germinate when the temperature is just right for them in the spring.
  • Seed packets that indicate stratification or a chilling period
  • Seed packets that indicate the seedlings can be direct sown as soon as the soil can be worked (I start these in January)
  • Seed packets that indicate the seedlings can be planted out before the last frost

How to Winter Sow Step-By-Step

In a nutshell, you will put a growing medium in a container, sow seeds, close the container and place it outside until spring.

Step 1: Choose and Prepare A Container for Winter Sowing

When Trudi Davidoff created the Winter Sowing method, she started with plastic empty milk jugs. I use milk jugs although my preference is gallon-size vinegar jugs. They are thicker plastic and a bit taller than the milk.

There are many different types of containers that you can use though. Part of the winter sowing methodology is to keep it low cost and that means using what you have available to you.

There are a few criteria that you need to be aware of. The containers need to:

  • have the ability to have drainage holes in the bottom
  • openings in the top to allow rain and snow to get in
  • clear top to allow light in
  • deep enough for 3-4″ of potting mix
  • tall enough for plant growth

Winter Sowing Container Ideas

If you don’t have your own supply at home to work with, try asking friends or relatives to save things for you. You might even try restaurants in your area. Remember, the side doesn’t necessarily need to be clear, but the top does.

Also, remember that you need room for the plant to grow up until you are able to transplant it out of the container.

And of course, the container should be clean to prevent diseases from forming. A wash with soap and water is fine. If you are reusing a container that had soil in it previously, make sure to rinse it with a bit of bleach in the water.

  • Milk, vinegar, or water jugs
  • Pet Food Containers
  • Storage Totes with or without pots or cups inside
  • Plant Pots with some sort of plastic covering (shower caps work great!)
  • Take out containers with high tops
  • Take out cake container with pots or cups inside
  • pop bottles

Putting Holes in The Containers

You need plenty of holes in the bottom of the container to make sure that it drains well. Too much water will cause the seeds and future roots to rot.

Holes in the top are also needed to allow water or snow into the container. This helps to keep the soil moist.

There are several different ways to put holes in the containers. I use a wood-burning tool because it is quick. A soldering iron or a hot glue gun is also very quick. There is an odor from the plastic burning so be sure to work in a well-ventilated area when using any of these tools.

An ice pick or awl will work if you slowly press it into the plastic. Stabbing will make these tools bounce off.

Making slits with a knife or box cutter works too and you’ll already have one of these for cutting the jugs open. Be very careful as they might slip around.

For a milk or vinegar jug, I put four holes in with my wood burner. They end up being about 1/4″ in size. I do not put the lids on the jug so there’s no need for additional holes on the top.

At this time, I also burn two holes in the side, one above and one below where I have made my cut. I use these holes to tie it closed which is just one way to keep the container closed. More information about sealing your containers is below in this article.

Adding holes to tie the jug shut with a wood burner.

If you are using anything that is holding multiple cups or pots, be sure to put a hole in the lid above each cup or pot. This ensures that each one gets enough water.

Step 2: Add Soil (Which Soil is Best For Winter Sowing?)

The best soil for winter sowing is not soil but a potting mix. Do not use a seed starting mix as it will not hold enough moisture. Select a quality potting mix that has a bit of plant food in it. I use Pro-Mix Premium Moisture Potting Mix, but something like Miracle Grow will work. Use an organic mix if you are starting vegetables.

Pre-moisten the mix with water. Put the potting mix in a large bowl or container, add water and stir. You want a consistency where it holds together a bit after you squeeze it but with no water running out of it. A tiny bit between your fingers is ok. You do not want it sopping wet.

Testing soil mix for moisture.

Put 3 to 4 inches of the pre-moistened mix into the bottom of your container. Do not press it in, you don’t want it to be compacted. I do tap the container once or twice on the counter just to settle it a little bit.

Step 3: Sow The Seeds

One of the most important things when sowing any seed is to know if the seed needs light or darkness for germination. If they need light, the seed packet will say something like “press into the soil”, “needs light to germinate”, or “barely cover”.

For seeds that need darkness, the seed packet will say to cover the seed. Most of the time the depth will be about the same size as the seed. Not always though, so be sure to do what the seed company recommends.

If your seed packet or envelope doesn’t have explicit directions, do an online search with the plant name plus ‘starting from seed’. One website that I refer to often is Johnny’s Selected Seeds. They have very detailed information on all the seeds they sell.

By now, you might be wondering how many seeds you should put in each container. Your decision is largely dependent on how many seedlings of each type you want.

For really tiny seeds, I try to evenly scatter them across the potting mix generally sowing a bit more than I think I might need.

For larger seeds, I’ll use something to make a hole and drop the seeds in. For something large like sweet peas, I might do a 9 or 12-per-gallon size container.

Germination rates are rarely 100%. This is why I always sow more than I think I need.

Step 4: Labeling

You must label your containers in a way that is permanent. The sun will fade a permanent marker in a heartbeat. Paint pens are a better option on the outside. Adding a UV protectant spray isn’t necessary but adds a layer of protection.

I use plant labels or cut-up window blinds and write on them with a pencil or china marker. They go inside and I push the marker down into the soil covering part of the words. If the upper part disappears, part of the name will at least help.

Hiding the label under the soil mix

You can also put duct tape on the bottom and write on it. Be sure not to cover the drainage holes.

A really cute idea is to use metal tags with numbers on them and to keep a log with the names in a spreadsheet. I’ve created a simple Winter Sowing Log in Google Sheets for you if that is the route you would like to take. You need to make a copy to be able to edit it. This spreadsheet is nice to use even if you aren’t using the numbering system.

Step 5: How To Seal The Container

The container can be sealed in several ways. The sides do not need to be airtight.

It can be duct taped or as I do, tied shut with a wire tie. I’ve also seen someone recommend just using a paperclip. Tying your container shut makes it much easier to check on the moisture content versus just peering through a hole in the top.

Tying the jug shut with a wire tie coated with plastic.

Of course, if you are using a storage container, simply removing the lid is the easiest.

Step 6: Where To Put The Containers Outside

After you have sealed your container it’s time to put it outside. Full sun is not necessary but access to rain and snow is. Protection from wind is essential as you do not want them to be blown over.

Placing them in a partially shaded area from the beginning can be a time saver. If the weather warms up quick in the spring, you do not want you new babies to get too hot and might need to move them.

Protection from animals is a consideration. If you have a dog that likes to throw things around, you might want to tie your containers down. A broom handle run through all the handles of jugs helps a great deal in securing them.

Step 7: When To Check The Containers

I check my winter sown containers once a week. Just a peek to make sure they have enough moisture. Depending on whether it has rained or snowed, they may or may not need water.

When spring rolls around, you’ll want to check on them more often due to increasing temperatures. If the soil looks dry, give them a drink!

Step 8: When To Transplant

The type of seed you have sown will determine when it is time to put your new seedlings in the ground. Some can be transplanted as soon as the ground can be worked, some just a few weeks before the last frost and many not until after the last frost in your area.

Be sure to check the seed packet for that information. If you use the spreadsheet I created for you, this information will be super handy and easier to access than your seed packet.

Winter sowing is an easy way to create many plants with minimal work and very little financial output.

One final word, don’t be discouraged if things don’t work out perfectly the first time you try winter sowing. Mother nature has her moods and even the wildflowers don’t always get their way. Learn from failures and rejoice in the victories.

Happy Planting!

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