Garden friends, today I am going to talk about winter sowing – Michigan gardening. I live in USDA hardiness zone 5b, so most of this will be for my zone but if your zone is warmer, you can start winter sowing earlier or if you are in a colder zone you will need to wait a little bit longer.
What is Winter Sowing
For people who live in a winter climate don’t usually think about planting seeds in the fall or the winter. Many perennials it is best to start them for winter sowing. Many flowers and some vegetables like a cold period, wet weather to germinate.
What is winter sowing? Winter sowing is a method of starting seeds outdoors in the winter. You would want to winter sow seeds that would require a cold stratification process or are cold hardy. The cold stratification process takes advantage of natural temperatures, rather than artificially refrigerating seeds.
Winter sowing seeds in a miniature greenhouse like a milk or water jug, outside during the winter, allowing the seeds to germinate in the spring when the conditions are right for them. The winter sowing method has been successful in most hardiness zones.
Don’t worry about seeds sprouting too early, hormones, waxes and heavy seed coats keep the seeds from sprouting at the wrong time. When you have freezing and thawing in cold moist soil breaks down, the seeds are ready to grow when spring arrives.
If you get unseasonably warm temperatures you will want to move them from the sun or open them up to not cook your seedlings, if they decide to sprout earlier than supposed to.
Winter Sowing Containers
To be able to do winter sowing, you need to use winter sowing containers that are translucent enough to allow the light to pass through them. You will also need to add hole to the bottom sides of the container for proper drainage and a lid that can be ventilated. If you use milk or water jugs, you can throw away the caps as they are not needed and that will be enough to ventilate and allow moisture to get in as well.
You can pretty much use any type of clear plastic containers for winter sowing. Other winter sowing containers that can be used is any plastic container, like take out containers, storage containers, plastic totes, pop and water bottles or even foil pans with plastic covers. Each container will need to be able to drain and allow ventilation.
How to Winter Sow
Here are some instructions on how to winter sow, in case you have never done it before.
- Use a translucent container, like a milk or water jug, pop/water bottles, 2 liter bottles, storage containers with a clear top or any type of container that is clear.
- Cut the water or milk jug below the handle to make a hinge and open the container
- Get some potting soil mix and pre-moisten the soil. Do not drench it, but wet enough to hold its form
- Add moist potting mix to each container
- Add seeds to each container, in a jug 6 to 10 seeds, 2 liter bottle maybe 2 to 3, follow sowing instructions on package
- Take duct tape and close the container and throw away the bottle caps and add drainage holes to the bottom of each container and ventilation to the tops of storage containers.
- Use a waterproof garden marker to mark what is growing in the container
- Place outside and let the magic happen when it’s time
Winter Sowing Advantages
There are many winter sowing advantages, see list below.
- Great for when you don’t have growing space or limited growing space indoors
- It’s simple
- Seedlings don’t get leggy because they are planted and grown outdoors
- No need to harden off seedlings and they are already acclimated to the weather conditions.
- Plant seedlings outdoors when conditions are the right temperature
- No grow lights or heat mats needed
- Prevents seeds from being eaten by critters outside or washed away
- Allows gardeners to start seeds early
As you can see winter sowing advantages is a great way to get your garden started. Winter sowing seeds gives flower and vegetables a head start. When winter sowing seeds make sure to not add too many seeds. You don’t want to damage the root ball by having too many seedlings in a container. It would be best to only do 6 to 10 seeds per jug or at least leaving approximately 2 inches between each seed for the best growing plants.
Not all seeds like to experience the cold germination and can cause the seedlings to fail. For gardeners who live in the north, is best to winter sow in late April, May and June depending on the seeds. It is best to read the seed package to know the heat requirements for germinating seeds and plan accordingly.
I use Johnny’s Select Seeds website – Starting Seed Date Calculator You just add your last frost date and it will calculate when to start your seeds and then look at the Johnny’s Select Seeds Key growing information. It detailed information on how to grow your seeds. Johnny’s has a ton of information on how to start your seeds and how to do succession planting.
Seeds I will be Winter Sowing
Below I am listing the seeds I will be winter sowing this year. This is not an exhaustive list but a list I will be doing. I may not be able to do all of these at once due to maybe not having enough containers but I will start and see what happens.
Berried Treasure White and Pink (Proven Winners) – both are everbarring and perennial for zone 4 – 9, both of these need cold stratification and would be perfect for winter sowing or if you want to start them indoors, put the seeds in the freezer for 3 to 4 weeks. They are best grown in containers, baskets and raised beds. Need full sun.
Walla Walla Onions (Botanical Interests) – these are a cold loving plant. These can be planted outside 4 to 6 weeks before your average last frost date or as soon as your soil can be worked. These will sprout in temps at least 45 degrees. Start these early for bigger onion bulbs.
Cabernet Onions (Botanical Interests) – these are also a cold loving plant. These can be planted outside 4 to 6
weeks before your average last frost date or as soon as your soil can be worked. These will sprout in temps at least 45 degrees. Start these early for bigger onion bulbs.
Spinach Baby Greens (Botanical Interests) – These can be planted outside 4 to 6 weeks before your average last frost date. When soil temperatures reach 40 degrees but ideally 50 to 75 degrees. These should be successive planting every 3 weeks until 4 weeks before your first fall frost date. This can be planted indoors anytime to grow and eat all winter long.
Mustard Giant Red (Botanical Interests) – These can be planted outside 4 to 6 weeks before your average last frost
date. When soil temperatures reach 40 degrees but ideally 50 to 75 degrees. These should be successive planting every 3 weeks until 4 weeks before your first fall frost date.
Mustard Southern Giant Curled – (Mountain Valley Seed Co) – This can be planted outside as soon as the soil can be worked and will need to harvest before the temperatures get hot. Select a sunny location and when temperatures reach 40 degrees, this can be successive planted as well.
Swiss Chard – Five Color Silverbeet – (Botanical Interests) – Recommended sowing 2 to 4 weeks before your average last frost date and when soil temperature is at least 40 degrees. This can also be direct sowed in the fall 2 months before first frost date. (protect from heavy frost).
Kohlrabi – Purple & White Vienna (MIGardener) – These are both cold tolerant, germination is best when temperatures reach 60 degrees. I have read where kohlrabi is one of the vegetables on peoples lists for winter sowing.
Cabbage – Green & Red – (Burpee) – can be planted 4 weeks before your last spring frost and is also container friendly. Avoid planting in garden area where cabbage family was grown the year before. Will withstand light frost.
Cauliflower – Cheddar, Denali, Lavender, Puntoverde (Johnny’s Select Seeds) – This is good for a winter crop where temperatures rarely below 32 degrees and would also work for winter sowing.
Bachelor Buttons – Blue Boy – (American Seed) – Sow in full sun to part shade, germinates with soil temperatures 60 – 65 degrees or direct sow as soon as soil can be worked. Sow 3-4 weeks before last frost date.
Bells of Ireland – (Botanical Interests) – Recommended 2 to 4 weeks before your average last frost date for chilling period. Seeds will germinate when soil temperatures are above 50 degrees.
Champion Blue & White Improved – aka Bellflower or Canterbury bells – (Johnny’s Selected Seeds) – these can be started in fall, winter, or early spring. Winter-sown plants flower in mid-jun through early July on shorter plants in spring tunnel trials at Johnny’s.
Delphinium – White King – (Eden Brothers) – This particular variety is considered an annual, there are over 300 species of delphiniums and some are perennials, or biennials. Planting in early spring is ideal for cold winter areas
Larkspur – Giant Imperial (American Seed) – These seeds are recommended to Pre-Chill seeds for 7 days at 35 degrees to improve germination. Darkness is required for germination. These seeds don’t germinate well when soil temperatures are above 55 degrees.
Love-In-A-Mist – Miss Jekyll Mix – (Baker Creek Heirloom Seeds) – This is considered a Hardy Annual with ideal soil temperatures between 50-70 degrees. Sow in place in late fall, winter, early to mid spring, full sun to part shade. Self-sows freely.
Orlaya – White Lace – (Botanical Interests) – Germination improves with seed cold stratification. For mild climates sow in the fall for winter blooms or spring blooms.
Poppy – the Giant & Double Mix – (Eden Brothers) – both require cold stratification, plant in full sun to partial sun location.
Stock – Katz Cherry Blossom – (Johnny’s Selected Seeds) – This is a cool weather crop. Stock is a member of the Brassica plant family and is susceptible to flea beetles. Cover plants with row cover at the time of transplanting. Expose seedlings to temperatures of 40-45 degrees for 3-4 days.
Blue Balloon Flower – (Baker Creek) – Zone 3-9, ideal temperatures 65-75 and frost hardy, needs 6-8 hours of full sun.
Carnation – Chaubaud Giant Mix – (Ferry~Morse) – likes to be planted in early spring when a light frost is still possible. Carnations like cool temperatures of 50-55 degrees to keep plants low growing and basal branching. This is considered a tender perennial.
Echinacea – White Swan – (Botanical Interests) – Zone 3-8 – Sow outdoors 2 to 4 weeks before your average last frost date or sow as late as 2 months before your average first fall frost date. Sow indoors 10 to 12 weeks before last frost date and might bloom the first year.
Marshmallow – (Baker Creek) – this needs to cold-stratify 4-6 weeks or direct sow in late winter or very early spring. Needs full sun 8 to 12 hours, frost hardy, ideal temperatures 60 degrees.
Milkweed – Butterfly Flower – (Botanical Interests) – Zone 3 and warmer. Help germination using cold stratification for 3 to 6 weeks. This is native to Eastern 2/3’s of the USA and Canada.
Penstemon – Dazzler Blend – (Botanical Interests) – Zone 4-8. This likes to be sown outside 6 to 8 weeks before your average last frost date or fall.
Poppy – Champagne Bubbles – Mix, White & Scarlet – (Johnny’s Selected Seeds) – Icelandic poppies perform best in cooler conditions below 70 degrees. Sow in early spring when soil is cool and a light frost is still possible.
Primrose – Pale Evening – (Eden Brothers) – Zone 4-9. A native North American wildflower.
Scabiosa – Pincushion Flower – Fama White – (Johnny’s Selected Seeds) – Zone 3-7. Sow 6 to 8 weeks before last frost is recommended.
Snapdragon – Magic Carpet Blend (Botanical Interests) – Zone 5 and warmer. Recommended in cold climates sow 4 to 6 weeks before your last average frost date or as soon as the soil can be worked. Freezing seeds for 48 hours prior to sowing aids in germination. Perfect candidate to just winter sow them.
Sweet Pea – Perennial Blend – (Botanical Interests) – Zone 3-8. Recommended in cold climates sow 4 to 6 weeks before your last average frost date or as soon as the soil can be worked
Winter Sowing Perennial and Hardy Annuals
As a rule, for winter sowing perennials and hardy annuals, if a plant is hardy in your zone, you can plant its seed anytime in winter, regardless of the temperature outside. Sprouting will occur when warmth arrives, normally in spring. However, the seed can also sprout during some freak warm spell between weeks of frigid conditions. This is not a problem for perennials and hardy annuals. They simply yawn in the face of frost. I live in zone 5b in Michigan and the perennial and hardy annuals can be winter sown in the months of January and February, along with the cold hardy vegetables and herbs.
Winter Sowing Tender Annuals
You can plant these early, too, with one important caveat: Should sprouting occur during a warm day (please note, it’s even warmer inside the milk-jug greenhouse), you’ll need to throw a blanket over the container at night because such seedlings are easily killed by frost. That’s why they’re called “tender.” Consequently, to avoid the covering-work, it pays to delay the sowing of tender annuals until March or April, depending on your grow zone. For the tender annual and herbs, March is a good time to start tender annuals, vegetable and herbs, for example are;
Tender Vegetables and Herbs
April you can winter sow tomatoes and peppers and other tender vegetables and herbs when in zone 5b.
I will be starting winter sowing sometime this week. I hope you found this helpful on when and how to start winter sowing. Again this post is based on my USDA Hardiness Zone 5b in Michigan. This is just a guide to help you decide what to winter sow and when approximately.
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