Winter Sowing Native Plant Seeds

Back in November, I began to expand my native garden plantings by direct sowing a number of native plant varieties. I chose that method because it seems like the most natural (and low effort!) way to sow the seeds. It’s hard not to acknowledge though that winter sowing could be a more reliable and successful method of planting my native seeds. So, again for the sake of science, I thought I would give it a try with a few varieties rather than all of my plants.

What is Winter Sowing?

Winter sowing is a seed starting method where you sow your seeds in a sheltered container, and set them outside for the winter. You don’t need any special containers to accomplish this. You can simply use water jugs or other reusable plastic containers with lids. Even though the containers have lids, you need to be sure that the lids have enough holes in them, so that some moisture can get into the seeds for germination and a hole for excess water to drain out the bottom. As the containers sit outside, they’ll get covered with snow and they’ll experience rain, snow, and all the other conditions that come with a good Canadian winter.

Why choose winter sowing?

I have to admit, I struggled with this question. Native plant seeds are tough; in nature, they distribute and germinate just fine without any help from us humans. Why would I need to do anything more than direct sow or even broadcast the seed? From what I’ve read so far it increases the potential for successful seed germination. Surely there must be more to it than that right?! Well, for the sake of objective learning and trying to create a successful landscape using mostly native plants, I thought I should explore this topic a little deeper.

Advantages of Winter Sowing Native Plant Seeds

First, let’s explore why you might opt for winter sowing despite the comparative ease of direct sowing:

1. Seed Protection: One of the best reasons for planting a native landscape is to support local birds, bugs, and wildlife. Part of that means that the seeds will become food for someone whenever they need it. By winter sowing, you protect your seeds from predation; that’s giving them a better chance of germination.
2. Natural Stratification: As I mentioned in my last article many native plant seeds require a period of cold stratification to break dormancy and germinate successfully. Winter sowing utilizes the natural cycles of the seasons, eliminating the need for artificial stratification methods like refrigeration. This can simplify the seed starting process and increase germination rates for species that require stratification.
3. Reduced Indoor Space Requirements: Another method of starting plants from seed involves starting them indoors, keeping them in a refrigerator and then starting them under grow lights or on windowsills. This can be challenging if you have limited indoor space or lack adequate lighting. Winter sowing allows you to prepare and keep your seeds outdoors, reducing the need for indoor seed starting setups or taking up space in your home.
4. Minimal Maintenance: Once seeds are sown in winter, they require minimal maintenance until they begin to germinate in spring. Unlike indoor seed starting, which requires regular monitoring and watering, winter-sown seeds can largely fend for themselves until warmer weather arrives. This can be especially beneficial for busy people or those who like to travel away from winter weather.
5. Hardier Seedlings & Better Adaptation to Local Conditions: Direct sow and winter-sown seedlings tend to be hardier than those started indoors. Exposure to fluctuating winter conditions helps to naturally harden off seedlings, and makes the plants more resilient to your local conditions once they begin growing. This can lead to earlier establishment and flowering, and better long-term hardiness of the plants in your garden. 

Disadvantages of Starting Plants by Winter Sowing 

Are there really any downsides to winter sowing native plant seeds? I think there are a few distinct drawbacks that need to be discussed:

1. Variable Success Rates: Success with winter sowing can vary depending on factors such as seed quality, weather conditions, container and soil preparation. Not all seeds will germinate, and some may succumb to environmental challenges like frost or excessive moisture.
2. Patience Required: Unlike buying established plants from a nursery, growing native plants from seed through winter sowing requires patience. It may take several months for seeds to germinate and for seedlings to reach a transplantable size. For some varieties, germination alone can take up to a few years, so it’s definitely not a method for those seeking instant gratification.
3. Risk of Frost Damage or Too Much Heat: Depending on your location and local climate, there’s a risk of frost or heat damaging emerging seedlings. While native plants are generally more cold-hardy, extreme weather events can still pose a threat. Young, tender seedlings sheltered in containers can be especially vulnerable to unexpected freezing or, if the lids are on during an unexpectedly warm day they can cook.  
4. Space Considerations: Winter sowing often involves using containers or makeshift seed beds, which may take up valuable space in your outdoor area. You’ll need to plan accordingly to ensure you have enough room in a somewhat protected area for your seeds and seedlings.
5. Transplanting Difficulties: depending on the number of seeds you start in a container, if you’re not able to get to them before the roots get entangled, you could have trouble successfully separating the seedlings for transplanting. I’ve also read that the shock of the transplanting process can be too much for seedlings if they’re pulled too soon. It sounds like you have to be vigilant of your timing at this stage. 
6. Too Much Success: I know what you’re thinking, how could too much success be a disadvantage!? Well, if you winter sow 15 varieties of plants, and for the sake of argument, each packet of plants contains 50 seeds, if all of those seeds germinate, you’ll suddenly have 750 little plants to deal with. Ok so even if they don’t all germinate, there’s still potential for a LOT of plants! You’ll either need lots of space in your gardens or you’ll need lots of friends to share with – not that that’s a bad thing. This can really make more work than you bargained for at an already very busy time in the garden. 

These last two disadvantages are the ones that make me the most nervous. At least with direct sowing I’ll never know exactly how many of my seeds have germinated and I don’t have to worry about transplanting them at a vulnerable stage. Even so, for the sake of science (and fun) I’m giving winter sowing a shot!

My Method for Winter Sowing Native Plant Seeds

Thankfully information about this method of planting is abundant online and almost everything I’ve read has similar steps even if the methods vary a little bit. So, taking the most common information, plus a few of my own touches I’ve come up with the following process: 

Prepare Your Containers

I used a combination of empty 4L water bottles that conveniently came into my possession, clean, empty salad containers and a seed starting tray with a lid. 

For the 4L bottles, I removed and disposed of the lid, then cut them at just about half and most of the way through so that they open wide like a muppet mouth. One day maybe I’ll remember to take pictures of all my steps! Until then, it’s kind of like this: 

For all containers I punched small holes in the lids to let a little more water into the container. The 4L water bottles were the hardest to do, so I lit a candle, warmed a piece of pointy metal with the flame, and melted holes through the plastic. Do the same with the base of the container to let excess water drain out. I did take pictures but it’s really hard to see holes in clear plastic. You get the idea though I’m sure!

Add Soil

If possible, fill your container up to about 4-5” if possible. I used a generic potting soil. In hindsight, I probably should have added a bit of extra perlite to lighten the soil but since I didn’t, I’ll just have to trust those tough little seeds to make do. 

Sow Your Seeds

Sow the seeds on top of the soil and put a sprinkling of soil over top. I’ve read that a good rule of thumb for seed depth is to base it on the size of the seed. Bigger seeds can have ¼” – ½” of soil overtop while tiny seeds can simply be pressed into the soil a little bit and do not need covering. I’m sure there are way more experienced people than me out there so if that doesn’t feel right to you, do more research!

Label, Close and Secure Your Containers

Close the containers and make sure to secure them well enough to endure the winter conditions they’ll be sitting in. I taped all of mine shut well.

Put Them In A Safe Place Outside

Put them in a safe place where they’ll get exposure to your winter conditions but won’t be at risk of damage due to traffic or extreme pressure. For example, you want to keep them away from your dog’s run and safe from crushing when the snow slides off the roof in a sheet. I put mine in the empty half of the compost bin.

What I planted by winter sowing: 

Plant	Status	Note
Blue Flag IrisIris versicolor	Common	From a friend’s seed stash!
Common MilkweedAsclepias syriaca	Common	From Northern Wildflowers
Fringed GentianGentianopsis virgata ssp virgata	Common	From a friend’s stash!
Wild ColumbineAquilegia canadensis	Common	From Northern Wildflowers

One thing I really enjoyed about winter sowing is that it got my hands in the dirt in February – that’s the middle of winter here! I might be cutting it close for the 6-10 weeks of cold stratification, and I may have forgotten to put holes in the bottom of one of my containers (I’m afraid to look), but I’ve got a good feeling about these tough little seeds.  

Overall, my impression of winter sowing native plant seeds is that, like direct seeding, it offers a cost-effective, relatively low-maintenance way to grow a diverse range of plants while supporting local ecosystems. While there are some challenges associated with this method, the benefits of connecting with nature, encouraging biodiversity in our landscape, and the potential to enjoy the beauty of native flora for years to come make it a worthwhile effort in my books.

I’d love to hear about your experience with winter sowing! Got questions? I’m not sure I’ll have the answers but I’ll give it my best shot! Leave a comment below or …

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