Freighter View Farms | Chris Izworski

Every February the grow light shelf fills up, and every February I find myself second-guessing the calendar. The seedlings look ready. The basement smells like spring. Outside, the bay is still frozen and the forecast shows two more months before it is safe to transplant. This is the tension that Michigan seed starting lives in — the season starting indoors long before the season begins outside.

The timing is everything. Start too early and you get root-bound, leggy plants that sit in their containers for weeks longer than they should, getting worse instead of better. Start too late and you lose weeks of the outdoor season that the short Michigan window cannot afford to lose. Here is the schedule I follow at Freighter View Farms, tested over enough seasons that I trust it.

The Anchor Date: May 15th

Everything works backward from the last frost. In Zone 6a on Saginaw Bay, that date is May 10th to May 20th — I use May 15th. Count backward from there to find the start date for each crop.

Early February: Onions and Leeks

Ten to twelve weeks before transplant. These are the slow ones — they need a long indoor season and they do not mind it. Start them in shallow trays under bright lights as early as the first week of February. The seedlings will look like grass for weeks. This is normal. They are doing their work underground.

Late February to Early March: Peppers

Eight to ten weeks indoors. Peppers germinate slowly and grow slowly and reward the patience required to give them a full indoor season. Shishitos, bells, sweet Italians — all of them want bottom heat at germination (a heat mat brings soil to 80°F and makes a visible difference in germination speed) and consistent warmth throughout the indoor period. Do not rush them. Peppers transplanted in mid-May after ten weeks under lights perform dramatically better than peppers started in late March.

Mid-March: Tomatoes

Six to eight weeks before May 15th puts the ideal tomato start date around March 15th to April 1st. This is later than most gardening enthusiasm suggests, and it is right. I have grown tomatoes started in early February — big, beautiful plants — that were root-bound and stressed by transplant time and never quite recovered their momentum. A tomato started March 15th and transplanted May 18th into warm, compost-rich raised beds runs down a big, early-started plant by mid-July.

Tomatoes do not need heat mats after the first few days — they germinate readily in the warmth of the grow light shelf, generally in five to ten days. What they need is plenty of light: twelve to sixteen hours per day under T5 or LED grow lights close enough to the tops of the plants that they stay short and stocky, not reaching toward inadequate light and going leggy.

Late March to Early April: Basil, Herbs, Flowers

Basil four to six weeks before transplant, which puts the start date in late March or early April. Earlier than this and the plants outgrow their pots. Zinnias and most annual flowers can be started in early April for transplanting in mid-May, or direct-seeded outdoors after last frost.

What Not to Start Indoors

Cucumbers, squash, beans, beets, carrots, radishes, and most root vegetables either do not transplant well or need only two to three weeks indoors at most. Cucumbers started in mid-May for transplanting in early June produce nearly as much as cucumbers started earlier — and without the root disturbance that stunts transplanted cucurbits. Direct-seed beans, beets, and carrots outdoors after last frost. The ground is ready for them then, and they prefer to find it themselves.

For zone-by-zone indoor start dates and germination timing, the national seed starting guide at chrisizworski.com is a useful cross-reference.

The window runs from first week of February to first week of April. Stay inside those dates, keep the lights close, water from the bottom, and what comes out of the basement in May will be ready for what the garden requires of it.

All of these dates are also collected in the Zone 6a planting calendar at chrisizworski.com.

Related reading:

• Every date in this calendar comes back to the last frost — Michigan Frost Dates: Zone 6a.
• Once the seeds are started, here is what happens in March in Michigan.

Seed Starting in Michigan: Common Questions

When should I start tomato seeds indoors in Michigan?

Start tomatoes indoors in mid-March in Zone 6a Michigan — 6 to 8 weeks before the May 15th transplant date. Starting earlier produces leggy, root-bound plants that struggle after transplant. Starting in March gives you compact, well-rooted transplants ready to go in the ground when the soil has warmed.

When should I start pepper seeds indoors in Michigan?

Peppers need 8 to 10 weeks before transplant, which means starting them in late February to early March in Zone 6a. Peppers germinate slowly at room temperature — a heat mat set to 80°F cuts germination time from 3 weeks to 10 days. Do not transplant peppers until nighttime temperatures are consistently above 55°F.

What do I need to start seeds indoors in Michigan?

The essentials: a light source that stays 2 to 4 inches above the seedlings (T5 fluorescents or LED grow lights work well), a heat mat for germination, a timer set to 14 to 16 hours of light per day, and a seed starting mix (not potting soil). A capillary mat for bottom-watering makes watering more consistent and reduces damping off. The full setup is in the capillary mats and grow lights post.

Why are my seedlings leggy?

Legginess almost always means insufficient light — either the light source is too weak, too far away, or the day length is too short. Move the light to within 2 inches of the seedling tops. If using a window, even a south-facing window in February Michigan provides only 4 to 6 hours of direct light — not enough. Supplement with grow lights.