When to Start Seeds in Zone 3

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?

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?

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

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

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

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

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

When to Start Seeds for Fall Planting

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

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.