Zone 6a Planting Schedule for Michigan
When to start, transplant, and direct sow — based on a May 10 last frost date
Key Takeaways
- Zone 6a in Michigan typically sees a last frost around May 10 and first frost around October 10
- Indoor seed starting begins as early as February for slow-growers like peppers and celery
- Most transplants go out in mid-to-late May after hardening off
- Succession planting extends your harvest through fall
Growing in Michigan’s Zone 6a means working with about 150 frost-free days and a last frost date that hovers around May 10 in most years. That’s a generous growing season for the Great Lakes region — enough to ripen tomatoes, grow full-size winter squash, and even coax along some crops that feel like they belong further south.
But the timing matters. Plant too early and a late frost kills your transplants. Plant too late and your tomatoes are still green when October arrives. This guide is the planting schedule I use at Freighter View Farms in Bay City — adjusted over years of watching what actually works on the western shore of Saginaw Bay.
February: The Slow Starters
Only a few crops need this much lead time. Peppers and celery both germinate slowly and grow at a pace that tests your patience. Start them indoors under lights by mid-February, ten to twelve weeks before your transplant date. Onions from seed need a similar head start — start them in late January or early February in a shallow tray, and don’t be alarmed when they look like sad grass for two months.
This is also a good time to check your seed inventory, test germination on anything older than two years, and order what you need. Seed companies start running out of popular varieties by March.
March: The Main Indoor Push
This is when most seed starting happens. Tomatoes go in around March 15 — eight weeks before transplanting. Eggplant around the same time. Broccoli, cauliflower, and cabbage can start in mid-to-late March for a late May transplant, or in late June for a fall harvest.
Herbs like basil, parsley, and cilantro do well started indoors in March. Basil especially benefits from the warmth — it germinates poorly in cool soil. Start it inside where you can control the temperature and move it out when nights are reliably above fifty degrees.
April: Hardening Off and Cool-Season Direct Sowing
As soon as the ground can be worked in April — when it’s thawed and dry enough that a handful doesn’t clump into a mud ball — you can direct sow cool-season crops. Peas, spinach, radishes, arugula, lettuce, and kale all go in four to six weeks before the last frost. These crops prefer cool weather and actually perform worse if you wait until it’s warm.
Mid-April is also when you start hardening off your indoor transplants. Move them outside for a few hours each day, gradually increasing their exposure to wind and direct sun over a week or two. This step is non-negotiable. A seedling that goes from a seventy-degree windowsill to a forty-degree, windy garden bed will stall out or die from shock.
May: Transplant Season
After the last frost — and I always wait until at least May 15, because the calendar is a suggestion and the weather has the final say — the warm-season transplants go in. Tomatoes, peppers, eggplant, basil, squash, cucumbers. All of them.
Direct sow beans, corn, and squash seeds once the soil temperature hits sixty degrees at a two-inch depth. A soil thermometer costs a few dollars and will save you from planting into cold ground, which is the most common cause of poor germination for warm-season crops.
This is also when you can direct sow a second round of lettuce, radishes, and other greens for a late spring harvest before the summer heat makes them bolt.
June Through August: Succession and Maintenance
Succession planting is the difference between a garden that produces for two weeks and one that produces for four months. Sow beans, lettuce, radishes, and cilantro every two to three weeks through June and into July. Each planting gives you a fresh wave of harvest.
In late July or early August, start your fall crops: broccoli, kale, Brussels sprouts, turnips, and a final round of lettuce and spinach. These will mature as the temperatures cool, and many of them — kale especially — actually taste better after a frost.
September and October: The Long Finish
Zone 6a’s first frost usually arrives around October 10, but I’ve seen it as early as late September and as late as Halloween. Watch the forecasts starting in mid-September and be ready with row cover for anything frost-tender that still has fruit ripening.
Root crops — carrots, beets, turnips, parsnips — can stay in the ground through light frosts. In fact, a frost converts some of their starches to sugar and improves the flavor. Mulch heavily and harvest through October, even into November in mild years.
Garlic goes in during October, four to six weeks before the ground freezes. This is the one crop you plant in fall for a harvest the following summer, and it’s worth every inch of bed space you give it.
For more on Michigan gardening, seasonal growing, and what’s happening in the garden right now, visit Freighter View Farms. I also post gardening updates and longer reflections on the growing life at LinkedIn and Medium.
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