How to Winter Sow Seeds in 7 Easy Steps

I don’t know about you, but after the holidays I’m already thinking about getting back out in the garden. Sadly, in my climate I can look forward to a few more months of snow and chilly temps.

 As a beginning gardener, I started my seeds indoors way too early. Planting early resulted in a variety of issues: weak seedlings from lack of light, some plants getting too big and requiring repotting, and a long hardening-off process. The whole ordeal took up a ton of space and time.

Good news for all of us impatient gardeners – winter sowing is the solution to all of these problems, and you can start as early as January! All you need to get doing are some simple items easily found around the house, making the process cheaper too.

Winter sowing is easy, fun, and yields great results. If you’d like a simpler, cost-effective way to start your seeds this year, here’s a step by step guide on how to get started.

What is Winter Sowing?

Winter Sowing is an easy method of seed starting. Even in cold climates, you let your seeds germinate outdoors, with the help of homemade mini-greenhouses. The seeds will sprout when the weather is warm enough, just like in nature! The result is less time spent, less space needed, and hardier seedlings.

Winter Sowing Benefits

Winter sowing has been a total game changer for me. Perfect for gardeners who just can’t wait to start their seeds or are low on space, this method might just be your new go-to! Here are some of the benefits of the winter sowing method.

When Should You Start?

My old chart for starting seedlings indoors was a bit of a beast. I listed all my plants and when to start them. I calculated how many weeks each needed to grow inside, counting back from my last frost date in May.

It was overwhelming and complicated. With winter sowing, none of that is necessary! This process is flexible, with no specific timing dictated for when to start.

Your climate and the type of seeds you plant will affect the process, but there’s no need to stress about getting it perfect. Don’t worry about the seeds freezing.

It won’t hurt them. Some people even store seeds in the freezer to keep them fresh! The point is to mimic the natural conditions of your area, while keeping your seedlings protected.

What You’ll Need

One of the best parts about winter sowing is that it uses readily available recyclable materials that won’t break the bank. You can use a variety of different containers, based on what you already have or prefer. Regular old potting mix works just fine, and nature will provide the rest! Here are the essentials you’ll need.

How to Get Started

Getting started with winter seeds is fairly simple. Once you have the basic household items you need to get started, it’s on to choosing seeds and starting the sowing process. Let’s take a deeper look at each step.

Step 1: Choosing Seeds 

Although you might find articles stating you should only start cold-loving crops like brassicas or hardy perennials when winter sowing, the truth is that you can winter sow pretty much anything.

Yes, winter-sown vegetables like brassicas may have an advantage because they love the cold, but most of the time, winter-sown containers keep seedlings warm enough where you don’t have to worry. The mini-greenhouses you construct will prevent damage from frost, and the seeds won’t germinate until their environment is warm enough.

 If you experience a lot of temperature fluctuation in the winter (very warm daytime temperatures followed by freezing nights), you may wish to start tender annuals a month or two later than your hardier plants.

Full disclosure – I start all my seeds at the same time, in jugs sitting right in the snow, and they all look great in spring!

If you like to play it safe, begin with seeds that need cold stratification (like many native perennials), or those that readily reseed in your area.

Some of the easiest tried-and-true seeds to begin with are leafy greens like lettuce and kale, or hardy veggies like broccoli and cabbage. Cold hardy perennial flowers do great as well.

Look for info on the seed packet to guide you (“cold tolerant, “direct sow in fall” or “early spring”, and “perennial” are all indicators the seeds will do well). Try delphinium, lupines, echinacea, hollyhocks, or poppies.

I’ve had no trouble with starting tender annuals in January, as the little greenhouse shelters them until temps are warm enough to sprout.

However, you can wait a month or two longer for cold sensitive plants like tomatoes, petunias, or nasturtium if this makes you nervous. The whole point is a more relaxing seed starting process!

Step 2: Prepare Your Containers

You can use many different containers for winter sowing. Whatever you choose needs to be clear (or only slightly opaque) to allow sunlight to penetrate.

Make sure there’s enough room for root growth (can fit at least 3-4 inches of soil). Containers will need holes for drainage and ventilation, but you can also cut or drill these yourself.

The most popular option is clear milk jugs, leaving the cap off for ventilation. Another widely used method is gallon-size plastic ziploc bags, where the zipper tops allow you to adjust as needed. However, you can also use take-home restaurant containers with lids, 2 liter soda bottles, or solo cups in a plastic tub.

For simplicity’s sake, I’ll just describe the process for milk jugs and ziploc bags here.

Step 3: Fill and Plant

Now you’re ready for the fun part! Fill your chosen container with at least 3-4 inches of potting soil. Sterile, light textured seed-starting mix isn’t necessary when winter sowing, as you are trying to more closely imitate outdoor conditions. Potting soil works great!

Next, moisten the soil thoroughly. You don’t want it to be soaking wet and soggy, but you want to start with soil that’s moist enough to stick to your finger.

Now you can sprinkle your seeds! You can plant them densely and thin them out later, or use only a few per container. The seed packets will give you recommendations for depth and spacing. Gently tamp them down and cover with a sprinkle of soil.

Step 4: Secure the Container

If using milk jugs, close the hinged lid and wrap the horizontal cut with sturdy duct tape. You will remove it and open the lids when you’re ready to plant, or to give large seedlings more sunshine on warm days.

For Ziplocs, close the top zipper most of the way, leaving a small section open for airflow. You can use clothespins to keep it open if needed.

Sometimes, Ziplocs can get floppy in rain and snow, so many gardeners keep them upright by stringing a skewer through the tops of several bags that can rest on the surface of a tub or tray. You can stick small branches in them vertically to hold the top erect.

You can be creative with what you have, but make sure the bags don’t get smashed and have room for seedlings to grow above the soil.

Next, label your containers! You can write on them directly with a sharpie, or use a paint pen. Make sure whatever you use can stand up to the elements.

Step 5: Pick your Location

Set your containers somewhere they’ll get plenty of winter sun and exposure to the elements. Rain, snow, and wind are good for them, and this exposure to outdoor conditions will result in hardy, robust seedlings!

If it’s so windy that you’re worried they’ll knock over, place them in aluminum trays or milk crates for extra sturdiness. Directly on the ground works just fine.

Step 6: Monitor Your Seedlings

Remember that seedlings grown with this method may take a while to germinate. The milk jug or plastic greenhouses will keep them warm enough to survive, but they can’t sprout until outside temperatures warm up. Don’t worry if you don’t see sprouts until early spring, depending on your climate.

I used to think that growing indoors gave me a big head start because they germinated earlier, but the truth is that winter sown seedlings usually fruit or flower at the same time as their indoor counterparts.

Even if they germinate slightly later, the increased hardiness and strength of winter sown seedlings helps them transition more easily, and they often outperform indoor transplants.

If you have plenty of rain and snow, you can ignore your containers until it’s time to plant in spring. If your winter climate is dry, you should check and water them as needed to keep them moist.

Check for sprouts at the end of winter or early spring. If seeds germinated quickly and are starting to outgrow the container, you can open the lids on warm sunny days, but make sure to cover them back up if temperatures dip.

Step 7: Transplant

Once all danger of frost has passed, you can transplant your seedlings directly into the garden! Gently separate their roots, or plant them in one big hunk, depending on how many you planted and their preferred spacing.

Winter sown seeds have great germination rates, and are already adapted to your garden conditions, making them an easy and cheap alternative to purchased nursery starts. You can now treat them as you would any other garden plant, and enjoy the fruits of your labor!