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20 Seeds To Start In March In The Canadian Prairies

by on March 13, 2024
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March is here and Spring is imminent for us gardeners living in the Northern Hemisphere. And damn does it feel good! March is also the month when seed starting really picks up. So much so that this article includes 20 seeds to start in March in the Canadian Prairies. Yes, 20!

This post is for gardeners living in Zone 3-5.

So get your seed starting gear ready and start planting.

Blog post collage of four photos with writing on top

Timing For March Seed Starting

By March, we are officially 12-14 weeks away from our last frost date in the Canadian Prairies.

And while that may still seem like a long time until we can get planting in the garden, March is actually the perfect time to start many veggie, herb and flower seeds indoors.

Here in Manitoba, my average last frost date is typically May 27. This classification is based on the last light freeze that is said to happen in the Spring. I use this date as my workbook schedule to guide all my seed starting.

I encourage you to go give my blog, The Ultimate Seed Starting Guide a read if you’re new to seed starting or just need a refresher. It is a detailed guide that walks you through supplies, set-up and best practices. Start there and then come back to this post to see the best 20 seeds to start in March in the Canadian Prairies.

You Don’t Need To Seed Start To Grow A Great Garden

Before we get into things, I always feel obligated to start these posts with the disclaimer that you don’t need to start seeds indoors to grow a great garden. Truly, you don’t!

You can wait until May before even thinking about your garden and still grow your own food successfully.

There’s hundreds of seeds that can be direct sown in your garden after your last frost date. So don’t stress! Do what works best for you.

Now let’s get into the 20 seeds to start in March in the Canadian Prairies!

I’ve broken this list into two sections.

Section 1: Seeds to start at the beginning of March (March 1-15).

Section 2: Seeds to start in the second half of March (March 17-31).

This is reflective of the days to maturity for each plant, so be sure to start these seeds within the suggested timeframe provided.

10 Seeds To Start In The First Half Of March In Zone 3-5

Kale, tomato, pepper and rudbeckia seeds and brown containers with text overtop

(14-12 Weeks Before Last Frost Date)

1. Eggplant

Purple striped eggplants grown in Zone 3

Eggplant is one of those vegetables I’ve always struggled with in the garden. My yields used to be really minimal and it would be well into August before I’d even start harvesting fruit. But then I started to seed my eggplants in early March and that extra indoor growing time made a huge difference! So, start your eggplant seeds inside at the beginning of the month.

Another pro tip for yielding lots of eggplants on each plant is to purchase a parthenocarpic variety. Parthenocarpy refers to the development of fruit without fertilization, meaning the flowers do not need to be pollinated to produce fruit. 

This makes a huge difference and allows you to grow eggplants in a warm greenhouse (eggplants love heat!) or in a garden space that doesn’t get many pollinators.

Best Eggplant Varieties For Zone 3-5:

  • Piccolo – striped parthenocarpic variety
  • Traviata – large dark purple fruit

2. Bell Peppers

Green bell peppers, start seeds in March in Zone 3

Bell peppers are another garden vegetable I wish were easier to grow! They have often given me the same struggles as eggplants with low yields and only a few fruits per plant. But starting the seeds inside in early March has also made a difference for me.

Plus, growing my peppers (both hot and bell peppers) in containers has made an even bigger difference. Containers help the plant’s roots stay nice and warm as oppose to in-ground where soil temperature fluctuates more often.

Best Bell Pepper Varieties For Zone 3-5:

3. Rudbeckia/Black Eyed Susan

Rudbeckia seeds to start indoors in March in Zone 3

Rudbeckia or Black Eyed Susan is one of the best annual flowers to grow in a Northern garden. It’s a native wildflower to most of Canada therefore does very well in our soils and extreme summer heat.

The yellow flowers are great for cut flower bouquets or just to add some colour to the garden.  Plus the blooms are extremely attractive to butterflies! So you can count of having lots of pretty butterfly friends visiting your garden if you grow rudbeckias.

When starting rudbeckia seeds indoors, sow the seeds on the surface of the soil just barely covered. The seeds are very fine but will germinate quickly if not sow’d too deep.

Best Rudbeckia Varieties For Zone 3-5:

4. Kale

Maggie holding handful of kale grown in Zone 3 garden

I love starting my kale indoors early in March. Now, you can definitely wait until later in the season to start kale or even just direct sow salad green kale seeds directly into your garden. But I find starting kale seeds in March allows me to grow plants that are 3-5 feet tall even in a short growing season!

You’ve likely seen photos of those massive kale plants, towering over the other plants in a garden bed. But in order to get your kale plants to that size in a Zone 3-5 garden, you have to start them early. I personally don’t find it a hassle because kale is so easy to grow.

Sow one kale seed per soil cell/block about 1/4” deep. Kale is pretty cold hardy, so you can transplant your seedlings into the garden before your last frost date.

Best Kale Varieties For Zone 3-5:

  • Lacinato – dinosaur style of kale
  • Darkibor – curly leaf, produces all season long

5. Snapdragons

Snapdragons are a really great annual flower and actually quite hardy in Zone 3-5 gardens as they are able to withstand a range of temperatures.

I really like growing snapdragons because the seeds are easy to save at the end of the season, which saves me money on my seed order the following year. I simply let the flower heads dry out on the plant and then shake the seeds into a bag. The seed heads look like little skulls!

Snapdragons do best when started indoors in early March at least 12 weeks before your last frost date. Sow seeds on the surface of the soil barely covered. I do find snapdragon seedlings have a tendency to dampen off, so be sure to remove the humidity dome and provide some air once germination occurs.

Best Snapdragon Varieties For Zone 3-5:

6. Ground Cherries/Gooseberries

Bowl of golden ground cherries in a paper husk

Oh, ground cherries! One of my all time fav garden treats. Ground cherries (or cape gooseberries) fall into the tomato family, but are a sweet treat with a flavour I can best compare to pineapple and vanilla. So sweet tasting and refreshing.

The plants resemble tomatillos with big, broad leaves and papery husks that the fruits grow inside. Ground cherries are so prolific in my garden, we are usually harvesting pounds every week by mid-August!

I do find ground cherries take longer to grow and mature than other tomato varieties. So I suggest starting in early March. Start the seeds as you would any other tomato seed in high quality seed starting mix and under grow lights.

Best Ground Cherry Varieties For Zone 3-5:

7. Stevia

Green leafy stevia plant with wide leaves

Also known as the “sugar plant,” growing stevia is an amazing way to organically grow your own natural sweetener in the garden. How cool is that? I’ve personally never grown stevia in my Zone 3 garden, but it is said to be very easy to grow after germinating.

Stevia is slow to germinate, sometimes taking up to 20 days before any growth emerges. Experts suggest using a heat mat for bottom warmth and, of course, grow lights are a must.

One of the fantastic things about growing stevia is that is produces new growth all season long, so you can continuously harvest. I love the idea of making my own sweet teas or desserts with homegrown sweetener.

Best Stevia Varieties For Zone 3-5:

8. Chrysanthemum

Feverfew flowers with white petals and a small yellow centre

Chrysanthemums fall into the shasta daisy family of flowers and can be started indoors at various times throughout the early Spring. But I find they bloom earliest in the garden if started in early March. You can also direct sow them after your last frost date, but you likely won’t have any blooms until August.

Chrysanthemums are another flower seed that germinate best when sow’d on the soil’s surface and barely covered. I do find they can take some time to germinate, but bottom warmth from a heat mat speeds things up.

Once transplanted in your garden, chrysanthemums will quickly blanket an entire area with little, delicate white flowers. They are so dainty to add to bouquets.

Best Chrysanthemum Varieties For Zone 3-5:

  • Madonna – hybrid that is very reliable

9. Tomatoes

Wooden box full of red and purple cherry tomatoes, big green beefsteak tomatoes and roma tomatoes

I start all my tomato seeds throughout the first half of March for my Zone 3 Manitoba garden. I personally find my tomato seedlings establish best in the Zone 3 garden if they are already quite mature once transplanted. For my tomatoes that I put in the greenhouse, I’lll even start them at the end of February since they’ll be transplanted in the greenhouse in late April – early May.

Tomatoes are very easy to start from seed indoors. Be sure to keep seedlings under grow lights that are only 2-3” above the tray. Otherwise, tomatoes have a tendency to get leggy and reach for the light. I also find potting up my tomato seedlings to larger containers (about 4–6” deep) sooner than later helps the plants stay happy indoors.

Best Tomato Varieties For Zone 3-5:

There’s so, so many fantastic tomato varieties to choose from! This list is simply a sampling of what I’ve grown over the last few years and loved, but please go and explore! 

10. Cabbage

Big green capriccio variety of cabbage with frilly leaves

Cabbage is a brassica that really benefits from being started indoors early in March. I typically start about half of my cabbage plants indoors in March and then another few plants in early July. This allows me to harvest a second succession of cabbage come Fall.

If you’re like me and love sauerkraut, kimchi and all things cabbage, I’d suggest doing the same! Plus, cabbage stores really well into Fall/Winter so you can enjoy it long after the gardening season is done.

Cabbage seeds are easy to germinate but the plants can be a little difficult to grow. My pro tip is to transplant your cabbage into the garden when temperatures are still cool before your last frost date. Cover the seedlings with a cloche at night to protect from any hard frost. Then come mid June, cover your plants with a row cover to protect from pests. Fertilize by top dressing with compost once every 3-5 weeks.

Best Cabbage Varieties To Grow In Zone 3-5:

10 Seeds To Start In The Second Half Of March In Zone 3-5

(12-10 Weeks Before Last Frost Date)

Cabbage, broccoli, cauliflower and flower seeds with brown pots and text overtop

11. Broccoli

Broccoli head growing in the middle of a plant surrounded by dark green leaves

Start your broccoli seeds indoors during the last week of March or as close as possible to the 10 week mark before your last frost date.

Like cabbage and other brassicas, broccoli is easy to germinate but can be tricky once seedlings are planted in the garden. The biggest challenge with growing broccoli in a Zone 3-5 garden is the pressure from pests, like cabbage moths. Covering your brassicas with a row cover makes all the difference. Though a row cover is a bit of an investment, it’s a purchase you only have to make once and can use for seasons to come.

When starting broccoli seeds, I sow 1-3 seeds per cell and then thin as they start to mature.

Best Broccoli Varieties For Zone 3-5:

  • Calabrese – cold tolerant, heirloom variety
  • Everest – produces broccoli nearly all season long

12. Cauliflower

All the same growing tips and challenges apply to cauliflower as the other brassicas just listed. And I have to say, in past years I haven’t even grown cauliflower in my Zone 3 Manitoba garden because of the frustration it caused me.

But, I do find if you can avoid having brassicas growing in the garden in late July-early August when pest pressure is the worst, you can actually enjoy a decent harvest. To capitalize on this small growing window, start your cauliflower in March, transplant out as soon as the soil is workable in the Spring and then you’ll be harvesting by mid-July. Then, you can start your second succession of brassicas mid August for a Fall harvest.

Best Cauliflower Varieties To Grow In Zone 3-5:

  • Trevi – pictured above, gorgeous green coloured heads
  • Skywalker – big, uniform heads
  • Mardi – tight heads that stay bright white

13. Basil

Maggie's hands harvesting purple basil leaves off the plant

Basil is a fast growing, vigorous herb that you may be surprised to see on this list of 20 seeds to start in March in the Canadian Prairies. Yes, basil can be direct sow’d in the garden or started indoors as late as May. But for a big, bountiful basil patch that produces new growth all season long, start your seeds indoors toward the end of March!

Basil is easy to grow from seed. I typically sow 2-4 seeds per soil cell and let them grow together until a few inches tall. I then separate the seedlings and transplant into larger containers before they’re ready to grow in the garden.

Basil is a tender annual herb, so be sure to wait until any chance of frost is long gone before transplanting out in the garden.

Best Basil Varieties For Zone 3-5:

14. Marigolds

Bright orange marigold flowers growing beside green leaves

Marigolds are one of my fav annual flowers and are very easy to grow. The perfect flower for my rookie gardeners out there!

Marigolds do best in the garden and put on early blooms when started indoors 10-12 weeks before your last frost date. But in past years I’ve started them as late as 8 weeks before my last frost and still had success.

Marigolds are easy to start from seed and germinate quickly. Just be careful that seedlings don’t dampen off. Be sure to remove the humidity dome and heat mat as soon as germination occurs.

Best Marigold Varieties For Zone 3-5:

15. Cosmos

Maggie holding a big bouquet of cosmo flowers different shades of pink

Cosmos are another easy-to-grow annual flower perfect for a Zone 3-5 garden. Cosmos make my list of 20 seeds to start in March in the Canadian Prairies because they bloom earlier if started indoors 10-12 weeks before your last frost date.

Some gardeners prefer to direct sow cosmos, which is definitely an option. Just set your expectations to not have blooming flowers until early August.

When starting indoors, sow seeds shallowly just barely covered in soil. The seeds are fine, so I generally sow a few seeds per soil cell/block and then separate once 3-4” tall.

Best Cosmo Varieties For Zone 3-5:

16. Asian Greens

From pac choi and boy choi, to shiso and tah tsai — there’s dozens of delicious and productive Asian greens that you can start indoors in March in the Canadian Prairies.

I like starting my Asian greens 10-12 weeks before my last frost date because it allows me to transplant mature seedlings into the garden. Plus, Asian greens are very cold tolerant and can withstand light frosts. So you can begin hardening them off in mid April in Zone 3-5 and have them transplanted in the garden by early May.

Best Asian Green Varieties For Zone 3-5:

17. Asters

Pink frilly china aster flower surrounded by greenery

I absolutely love the look of asters both in the garden and when added to bouquets. But asters can be a little challenging to grow in the Canadian Prairies.

Asters are very prone to dampening off. In my experience, if the seedlings don’t have a fan blowing on them they will quickly die. So be sure to have a small fan in your seed starting station. When it comes to transplanting in the garden, be sure to give your asters lots of growing room as they can get large and bushy. I like to mulch around the roots of my asters with straw to keep the roots cool during our Manitoba summer heat waves.

Best Aster Varieties For Zone 3-5:

18. Celosia

Dark red spikey celosia flowers

Celosia is a new-to-me cut flower that I’m excited to add to my garden this season. It is said to be extremely heat and drought tolerant and produces blooms throughout most of the season. I can’t wait to give it a shot!

According to my preferred seed company, West Coast Seeds celosia does not like its roots disturbed when transplanting, so be very gentle with your seedlings.

Best Celosia Varieties For Zone 3-5:

19. Strawflowers

Delicate yellow, orange and pink straw flowers with papery petals

Strawflowers are the wow flower in a cut flower bouquet. The first time I grew Strawflowers I was like “wait, what?!” The papery texture, the dozens of layers of petals, the tiny flower heads, the variation of colours…the wow factor is serious with Strawflowers. As the name suggests, the petals really do have a dry, straw-like feeling to them.

In Zone 3, I typically start my Strawflowers indoors in mid-to-late March. I sow the seeds just on the soil surface as they need light to germinate. I then water from below using a second tray underneath my cells that I fill with water.

Best Strawflower Varieties For Zone 3-5:

  • Sultane – mix of great colours, very productive

20. Yarrow

Yellow yarrow flower in a field of pink yarrow

Yarrow is another fantastic cut flower that makes such a nice filler in bouquets. I especially love yellow yarrow varieties. The golden flowers kind of have a vintage, old world vibe to them. Plus, yarrow is a perennial hardy to Zone 3! Perfect for the Canadian Prairies.

The last week of March is the sweet spot for me for starting my yarrow seeds indoors. Germination can be slow with yarrow, so be patient! I have sometimes waited more than 30 days for my seeds to sprout. But bottom heat and humidity domes are a great help.

Yarrow is cold tolerant and tough! To overwinter my plants outdoors, I cover with a thick layer of leaf mulch in the Fall. It provides insulation and protection from the extreme cold.

Best Yarrow Varieties For Zone 3-5:

And there you have it!

Blog post collage of four photos with writing on top

That was 20 seeds to start in March in the Canadian Prairies.

I hope you found this article useful and can apply it to your own seed starting this season. If you have any unanswered questions, comment below! I answer all your comments.

And if you’re looking for more organic gardening advice, be sure to check out the blog. I publish new content each week geared toward Canadian gardeners growing in short seasons and cold regions.

You can keep up with my garden over on Instagram too. I love building community with you over there!

Happy seed starting!

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Latest Comments

  1. March 12, 2022

    Hey Maggie, what do you think about heat mats? when do you turn off your heat mats? I find my celery and Scots pine have gone leggy. I know mats are supposed to be turned off after plants have sprouted, but I find when sowing a flat of plugs of different things obviously they sprout at different times. Theyre getting 16+ hours of light. So I wonder in this case if I should just ditch the mats all together and embrace the longer (but hopefully less leggy) germination? Thanks! Looking forward to new grow guides!

    — Matt
  2. March 17, 2022

    Hey Matt! I like heat mats. I don’t think they’re essential to successful seed starting but I have found they definitely speed up the germination process. I just have one heat that I alternate between my newly sown trays. I keep them on 24/7 but remove seeds from the heat mat after everything has germinated. 16-18 hours of light is the ideal length, so I wouldn’t be concerned about that. Maybe try lowering the lights so they are closer to the tops of your seedlings? I keep my lights just 3-4″ above and gradually raise the height as the plants grow. I generally find leggy plants means they’re reaching for more light. Good luck!

    — Maggie
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  15. March 27, 2023

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