Winter Sowing 101

So what is winter sowing? Many of you probably think it’s the same as winter growing. Winter growing is when we grow crops outside during winter. Winter sowing is different in that it is done in late winter but not directly in the garden. Winter sowing is completely different as you plant seeds in containers and place them outside during the winter months. The container acts as a small greenhouse for the seeds you plant. When conditions are perfect your seeds will grow. 

Winter Sowing 101
Clematis needs a cold period to germinate from seed

The effect of seeds being treated with cold temperatures is called stratification. Many seeds such as those of perennials like to have a cold treatment. This is an excellent way to start perennial seeds like Clematis for your garden and not pay the high prices at the garden centers. What we are doing is mimicking what mother nature would do by dropping seeds to the soil. With winter sowing the seeds have a better chance of surviving. 

The benefits to winter sowing are:

1. Plants are hardier than ones grown in the house.

2. You can grow hundreds of plants in a small space outside.

3. Saves money.

4. Easy to do.

5. Makes use of items that we would recycle.

6. You don’t need a greenhouse, grow lights or electricity.

7. You know the quality of the vegetables you are growing.

8. Fun to do during the cold days of winter with children.

Winter Sowing 101

Do you need any special supplies?

Do you drink milk, juice or pop? I imagine you drink at least one of the above. What you will need is a few clean milk jugs, pop bottles or salad packs, things you would be recycling. Avoid using containers that contain toxic products. You will need a pair of scissors, some duct tape, seeds, a felt marker, labels so you don’t forget what you plant and a good quality potting soil. 

How do we get started?

The first step is getting your containers ready. Rinse out your milk jugs a couple of times so they are clean. The next step is to make four drainage holes on the bottom of the jug. I find this is easiest done by starting your cut with an exacto knife and finishing it off with scissors. Drainage is one thing you cannot forget as your containers will be outside when we get rain and snow. A soggy wet soil means your seeds will rot. Once you have your drainage holes cut, remove the cap from the jug and recycle it. This is how moisture will enter the jug. If you are using salad packages be sure to punch holes in the top as well as the bottom so moisture can get at your seeds. Now that you have your drainage holes made its time to cut the jug in half.  Start to cut your milk jug near the handle and cut all the way around the front and to the opposite side of the handle but leave the handle attached.

So what soil do we use?

 I like to use a good potting soil. The first time I tried this I used a seed starter mix but it doesn’t contain enough nutrients to last until you can safely move your plants to the garden. This year I will be using a potting mix that has worked for me in the past. Whatever you use, don’t use garden soil. Its way to heavy and may not drain well and it may contain pests or disease. You want to fill your milk jugs so that you have at least 4” of soil inside. Moisten the soil well before planting your seeds. (Tip: I marked the 4″ level using a marker before I cut the milk jug open.)

Winter Sowing 101
Peas are hardy annuals & like cool weather.

What  and when can we plant?

Plant perennial and hardy annual seeds first. I started by trying a few perennial seeds of Dianthus and Chrysanthemums and  spinach and broccoli plants as they could go outside earlier than other plants.The harder your winter, the later you start so if you lived up in northern BC you would start later. I was skeptical about this method and was surprised to see how easy everything grew.  Basically the milk jug acts like a miniature greenhouse. Your seeds will germinate when environmental conditions are right. In March, you would start your annual plants like tomatoes, basil, etc. Cool season plants can be stared as early as January and February.

Number of seeds to use?

The number of seeds in one container-depends on type of plant being grown. Six to eight seeds is a good rule of thumb for the first year as it will make them easy to separate when transplanting them. The smaller the container, the less seeds you plant. For example, one to two seeds in a one litre pop bottle, four seeds in a two litre jug and 10 seeds in a salad pack tub. Leave an inch or two between seeds when planting.


Moisten the soil well before planting your seeds. Once the seeds are planted add a bit of soil to cover your seeds.

Winter Sowing 101
Spinach germinated in February!


Be sure to label both inside and out. I use a permanent marker to label the name of the plant on the duct tape but it can fade in the sun. It’s best to insert a label inside the jugs before sealing it up.

Winter Sowing 101
Perennial Dianthus winter sown in January

Sealing the container

Once your seeds are planted and watered its time to close the jug. This is why we need duct tape. Why duct tape? It seals well. You want the jug to be like a greenhouse so you should see condensation on warm sunny days and this helps to keep  the soil moist.


Only water if the jugs start to dry out. I found I didn’t have to water until spring when everything was actively growing and the weather had warmed. We have a lot of rainfall from January to March so April is when I began to check for dryness. 

Winter Sowing 101
Violas grow by winter sowing

When do we place the jugs outside?

 Wait until its frozen outside. Usually January or February is a good time to start. It all depends on what you are planting. Remember certain seeds need a cold period. Here on the west coast we don’t freeze for long so I place my jugs outside when temperatures dip to near freezing. 


I have found that a place that gets morning sun and afternoon shade works well. I have mine on the east side of my home. Some say its best to place them where they will be transplanted. Many of our community gardeners placed their jugs on their allotment  beds where they would be planted. The thought behind it is that the seedlings get used to the climate of that area.

Winter Sowing 101
Broccoli ready for transplanting

Do I have to transplant them to the garden?

No, you can continue to grow your plants in the milk jugs. You will need to fertilize them as they grow. Plants like salad greens, chives and other herbs will do fine. Think of it as a container garden for your balcony or patio. You could pop the jugs into a long wooden planter if you find it more pleasing to the eye. Before transplanting, open lids for a few days and let your plants get used to the weather.

What if it snows or is windy? 

If it snows which isn’t likely here they will be fine. Now if we get two feet of snow I would brush the snow off to reduce the weight or move your containers somewhere more protected. I actually place my containers in rows on a three-tiered plant shelf near the house. Its only two steps outside my back door so it makes it easy to check on them during bad weather. Windy days mean they should be in a sheltered area. On windy days, run a stake or twine between handles to secure them or bring them close to the home. 

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