When to Begin Seeds in Zone three

Even if you’re a diehard gardener who keeps your plants going throughout the winter, the arrival of spring brings new possibilities. Longer days and warmer temperatures cause overwintering perennials to send up new growth and nudge you to plant new seeds.

If you live in zone 3, it sometimes feels like winter will never end. By the time summer arrives, it seems like you snap your fingers, and it’s time to harvest the last of your ripe tomatoes and cover tender greens with row cover. Starting seeds at the right time is crucial to getting the most out of your very short growing season.

Let’s look at the key characteristics of zone 3 and the factors that impact when you should start your seeds in the spring. I’ll also provide an overview of when you should start common vegetable and flower seeds to get your garden started on the right foot.

Where is Zone 3?

Pick cold-hardy flowers like violas for a longer bloom season.

Zone 3 is the coldest hardiness zone in the continental United States, so it’s reserved for the chilliest regions of the country. These areas experience low temperatures that range from -30 to -40°F.

After the recent changes to the USDA Plant Hardiness Zone Map, zone 3 includes large areas in:

  • Northern Minnesota
  • North Dakota
  • Montana
  • Maine
  • High-altitude areas in Wyoming

Some towns located in this zone include:

  • Bemidji, Minnesota
  • West Yellowstone, Montana
  • Belcourt, North Dakota

What Is the Climate in Zone 3?

Cherry tomatoes still growing under a coating of snow. Expect a short growing season and an approximate last frost between mid to late May.

Scientists determine hardiness zones based on the lowest annual temperature rather than the average last frost date, the number of frost-free days, or the highest annual temperature. However, you can use the hardiness zone to infer other information.

Since these regions experience such cold winter temperatures, it takes a while to warm up in the spring. You can expect your last frost to occur sometime from mid to late May.

While the summer brings long days and warm weather that allow crops to thrive, the growing season is short. Temperatures begin to drop in the late summer, and the first frost usually arrives sometime in September. Using high tunnels, cold frames, and row covers can help you extend the growing season, but don’t expect to produce tomatoes and peppers on par with those grown in zones 6 or 7.

How to Determine When to Start Seeds

Gardener sowing seeds into seedling trays.Timing is very important when starting seeds indoors.

The last frost date plays a big role in when you should start your seeds indoors. If you plant too early, you’ll end up with seedlings bursting out of their containers by the time it’s safe to plant them outside. But if you plant your seeds too late, you’ll miss capitalizing on the first few weeks of your short growing season.

Once you have your last average frost date on hand, use this date to determine when you hope to transplant seedlings outdoors. Cold-hardy crops like kale, bok choy, and cabbage can withstand a bit of light frost, so you can transplant seedlings outdoors a few weeks before the last frost date, especially if you protect the seedlings with row cover. However, you should wait until a few weeks after the last frost date to transplant frost-sensitive crops like tomatoes, cucumbers, and basil.

Use the intended transplanting date to determine when to start your vegetables indoors. If you need a bit of help, turn to the seed packet. For example, the ‘Sun Gold’ packet instructs you to start seeds 4 to 6 weeks before your intended transplant date. If you expect the weather to be sufficiently warm by late May, you would want to start ‘Sun Gold’ seeds indoors sometime between April 8 and April 20.

When to Start Seeds

If you want to skip the work of figuring out when to start seeds, I’ve got you covered. I used the ideal planting time and the time it takes for seeds to grow into transplants to calculate the best time to start common crops in zone 3.

When to Start Vegetable and Flower Seeds Indoors in the Spring

A close-up of various basil seedlings in an indoor seed tray, showcasing vibrant green leaves and delicate stems sprouting from seeds. Each seedling is labeled with name tags, showing signs of healthy growth and promise.
Start seeds indoors to extend the growing season.

Starting seeds indoors allows you to get a jump start on the growing season and grow longer-season crops like tomatoes and peppers. Since the growing season is so short, I recommend starting seeds indoors rather than direct seeding.

Although everyone in this zone experiences cold and long winters, the exact last frost date varies by location and year. That means I’ll give you a range of dates to start your seeds rather than a single date. If you’re dealing with an unusually long winter or prefer to err on the cautious side, start your seeds near the end of the range.

It’s advisable to check the average last frost date for your exact zip code. This ensures you’re planting at the perfect time for your area.

If you start your seeds on the earlier side of the recommended dates, your seedlings may be ready to transplant before the last frost arrives. This isn’t a big deal for cold-hardy crops like broccoli, cabbage, and lettuce.

Harden the seedlings off, pop the plants on the ground during a warm day, and cover them with row cover. The row cover will help protect the seedlings against frost and wind as they acclimate to their new environment.

Chart: Zone 3 Indoor Seed Starting Dates

Alyssum April 1 to April 15
Basil April 10 to April 25
Bok choy April 1 to April 15
Broccoli April 1 to April 15
Cabbages April 1 to April 15
Calendula April 1 to April 15
Cauliflower April 1 to April 15
Celery February 20 to March 5
Celosia March 15 to March 30
Chard April 10 to April 25
Collards April 1 to April 15
Cucumber April 20 to May 10
Delphinium February 15 to March 1
Eggplant March 1 to March 15
Fennel April 1 to April 15
Kale April 1 to April 15
Lavender February 20 to March 5
Leeks March 1 to March 15
Lettuce April 1 to April 15
Melons April 20 to May 5
Onions March 1 to March 15
Parsley March 15 to March 30
Peppers March 25 to April 10
Spinach April 1 to April 15
Summer Squash April 20 to May 5
Tomatoes April 1 to April 15
Zinnias April 15 to April 30

When to Direct Seed Flower and Vegetable Seeds Outdoors in the Spring

A gardener direct sows seeds into a row  in rich soil. Some seeds perform better when direct sown.

While starting seeds indoors allows you to get a jumpstart on the growing seasons, not all crops transplant well. Direct seeding root veggies and tender-rooted flowers gives you the greatest chance of success. Most seeds germinate more slowly in cooler soil, but as long as the seeds remain moist and avoid rotting, they’ll emerge by the time the last frost arrives. Adding a layer of row cover over the freshly seeded beds warms the soil and speeds up germination.

I’ve listed the preferred dates for the first round of direct seeding. But this first round doesn’t have to be your last round! Remember, you can succession plant another round of seeds two or three weeks later to enjoy a continuous harvest. Confirm your final frost date and adjust the timing to suit your region’s average conditions.

Chart: Zone 3 Direct Sowing Dates

Arugula April 15 to April 30
Bachelor’s Buttons May 1 to May 15
Beans May 30 to June 15
Beets April 15 to April 30
Carrots April 30 to May 15
Cosmos May 15 to May 30
Peas April 15 to April 30
Poppies April 1 to April 15
Radishes April 15 to April 30
Turnips April 15 to April 30

When to Start Seeds for Fall Planting

A close-up of broccoli microgreens, displaying tender, tiny leaves with intricate textures and shades of green. These young seedlings are thriving in a large transparent container, showing early signs of robust development and freshness.
Planning for fall crops makes the most of the last chance for the year’s harvest.

It’s easy to enter the spring growing season with unbridled enthusiasm. But it’s a bit more challenging to plan for fall crops. For zone 3 gardeners, fall planting coincides with summer tasks like trellising tomatoes, picking cucumbers, and keeping on top of summer weeds. If you remember to start autumn seeds around this time, you can get transplants in the ground and enjoy a bountiful harvest when colder weather arrives.

Zone 3’s short growing season means you should transplant fall crops in early to mid-summer. If you hope to harvest fall crops, start your seeds during the following dates.

Are you prone to experiencing earlier winters each year? In that case, check your first frost date in the fall and adjust the dates below to ensure your plant can reach maturity before those dates arrive. Be sure to check your variety’s average days to maturity to make sure your timing is right!

Chart: Zone 3 Fall Seed Starting Dates

Bok choy June 15 to June 30
Broccoli June 1 to June 15
Cabbages June 1 to June 15
Cauliflower June 1 to June 15
Chard June 1 to June 15
Collards June 1 to June 15
Fennel June 1 to June 15
Kale June 1 to June 15
Lettuce June 1 to July 1
Spinach June 15 to July 15

Final Thoughts

Whether planting seeds indoors or directly seeding into your garden, starting seeds at the proper time will help you make the most of zone 3’s short growing season.

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