If you’re a gardener in the Great Lakes State, knowing when to plant seeds in Michigan is the first step to a successful harvest. Our unique climate, with its late springs and early frosts, makes timing absolutely critical.
This guide will walk you through the optimal schedule for sowing everything from hardy greens to tender tomatoes. We’ll break it down by region and plant type, giving you the confidence to get your seeds started at just the right moment.
When to Plant Seeds in Michigan
Michigan’s planting calendar is primarily dictated by frost dates. The average last spring frost can range from early May in southern areas to early June in the Upper Peninsula. The first fall frost often arrives by late September or early October.
Your local frost dates are your most important piece of information. You can find them through your local MSU Extension office or reliable gardening websites. Always treat these dates as estimates, as weather can vary significantly from year to year.
Understanding Your Michigan Growing Zone
Michigan spans USDA Plant Hardiness Zones 4 through 6. This means winter lows can range from -30°F in the north to -10°F in the south. Your zone helps you choose perennial plants that will survive winter, but for seed starting, frost dates are more directly relevant.
- Zone 4 & Upper Peninsula: Shortest growing season. Rely on cold-hardy crops and consider season extension techniques like cold frames.
- Zone 5 (Northern Lower & Central): A moderate season. You can grow a wide variety but must be mindful of frost dates.
- Zone 6 (Southern Belt along Lake Michigan): Longest, warmest season. You can plant tender crops a bit earlier and enjoy later fall harvests.
Spring Seed Starting: The Early Birds
Some seeds actually prefer cool soil and can be sown as soon as the ground is workable in spring. “Workable” means it’s not frozen and not so wet that it forms a muddy ball in your hand.
These cool-season crops can tolerate light frosts. You can sow them directly in the garden 4-6 weeks before your last expected frost date.
- Peas
- Spinach
- Kale
- Lettuce & Arugula
- Radishes
- Carrots
- Beets
Starting Seeds Indoors for Spring
For warm-season crops, you’ll need to start seeds indoors. This gives them a head start so they can produce a harvest before fall frost. The general rule is to start seeds indoors 6-8 weeks before your last frost date.
- Calculate your last frost date (e.g., May 15th).
- Count back 6-8 weeks (e.g., March 15th – April 1st).
- Plant seeds in sterile seed-starting mix, not garden soil.
- Provide ample light—a sunny south window is good, but grow lights are often better for sturdy seedlings.
- Keep the soil consistently moist but not soggy.
- Harden off seedlings for 7-10 days before transplanting them outside.
Summer Planting for Fall Harvests
Many gardeners forget about planting in summer, but it’s key for a continous harvest. As soon as spring crops are finished, you can replant that space.
In mid-to-late summer, you can sow seeds directly for crops that mature in cool autumn weather. Calculate planting dates by looking at the “days to maturity” on the seed packet and counting back from your first fall frost date.
- Direct sow bush beans in early July.
- Plant carrots and beets in late July for sweet fall roots.
- Sow another round of lettuce and spinach in August.
- Kale and collards planted in summer become especially sweet after a frost.
A Regional Month-by-Month Guide
Here’s a general timeline. Always adjust based on your specific location and that year’s weather patterns.
March – April
Indoors (All Regions): Start seeds for tomatoes, peppers, eggplant, broccoli, cabbage, and herbs. Outdoors (Southern MI, late April): If soil is workable, sow peas, spinach, and radishes. The Upper Peninsula will still be waiting.
May
Early May (South): Direct sow carrots, beets, and lettuce. Transplant hardened-off cool-weather seedlings. Late May (South & Central): After frost danger passes, transplant tomatoes and peppers. Direct sow beans and corn. Upper Peninsula: Outdoor planting often waits until late May or even June.
June
Early June (All Regions): The coast is generally clear for all transplants and direct sowing of warm-weather crops like cucumbers, squash, and melons. Succession plant more radishes and lettuce.
July – August
Focus on fall harvest. Direct sow carrots, beets, bush beans, and start your fall greens like kale and Brussels sprouts indoors for later transplant. Its also a good time to plant a cover crop in any empty beds.
Tips for Success in Michigan’s Climate
Our weather can be unpredictable. These strategies will help you adapt.
- Use a Soil Thermometer: Warm-season crops like cucumbers need soil at least 60°F. Planting in cold soil leads to poor germination.
- Protect Early Plantings: Keep row covers, cloches, or even old milk jugs on hand to protect young plants from a surprise late frost.
- Mind the Microclimates: Urban areas and spots near large bodies of water (like the Great Lakes) are often warmer. A south-facing slope warms faster than a north-facing one.
- Keep Records: Note planting dates, varieties, and harvest times in a garden journal. This is your best tool for refining your timing each year.
Common Seed Starting Mistakes to Avoid
Even experienced gardeners can make these errors. Being aware of them helps you succeed.
- Starting Too Early: This leads to leggy, root-bound seedlings that struggle after transplanting. Don’t rush spring.
- Insufficient Light: Seedlings become tall and weak stretching for light. Provide bright, direct light immediately after germination.
- Skipping Hardening Off: Moving seedlings directly from indoors to the garden shocks them. Gradually expose them to sun and wind over a week or two.
- Planting Too Deeply: A general rule is to plant a seed twice as deep as it’s width. Tiny seeds like lettuce need just a light covering.
FAQ: Your Michigan Seed Planting Questions
When is the best time to start flower seeds in Michigan?
Annual flowers like marigolds and zinnias are started indoors 6-8 weeks before the last frost, similar to tomatoes. Hardy annuals like poppies can be sown outdoors in early spring.
Can I plant seeds in May in Michigan?
Absolutely. May is a prime planting month. Early May is for cool-season crops and transplants, while late May is for warm-season crops after frost danger passes.
What seeds can I plant in June in Michigan?
You can still plant fast-maturing crops like beans, cucumbers, summer squash, and basil. It’s also the perfect time to start seeds for fall harvest, like carrots and broccoli.
How late can you plant a garden in Michigan?
For fall harvest, planting extends into August for greens and radishes. Garlic is planted in late October for next summer’s harvest. The season is longer than many think!
Should I adjust for a late or early spring?
Yes, always. Use soil temperature and frost forecasts as your real-time guides, not just the calendar. A warm April might let you plant early, but be prepared to protect tender plants if cold returns.
By following this schedule and paying attention to your local conditions, you’ll master the art of timing in your Michigan garden. Remember, gardening is an experiment every single year, so take notes, learn from what works, and enjoy the process of growing your own food and flowers from tiny seeds.