Michigan · zones 4b–6b
When to plant broccoli in Michigan.
Sow or transplant between Mar 14 to Apr 11 in a typical year, keyed to Michigan's median last frost around May 5. A second, fall sowing fits Jun 24 to Aug 3. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Broccoli dates for a typical Michigan season.
1 · Start indoors
Jan 31 to Feb 28
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Mar 14 to Apr 11
Keyed to the ~May 5 last frost. Sow 0.5" deep, 18" apart.
Fall round
Jun 24 to Aug 3
Counted back from the ~Oct 8 first frost.
Harvest
~60 days later
~1.2 lb per plant over ~3 weeks.
Michigan spans more than one climate: Zone 6 is the most common zone, but the state runs 4b to 6b. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
Michigan growing notes
Michigan grows one great broccoli crop, not two.
Why Michigan skips Alabama's two-crop scramble
Growers in the Deep South split broccoli into a rushed spring race and a big fall crop because their springs turn to summer heat almost overnight. Michigan does not have that problem nearly as badly. The state's Great Lakes shoreline counties especially run cooler and more even through early summer than inland regions at the same latitude, because the lake absorbs heat slowly and releases it back gradually, which holds air temperatures down through the exact weeks broccoli needs to form a tight head instead of a loose, bolted one.
That does not mean spring broccoli is foolproof here. A head that is forming when a hot stretch hits will still rice, meaning the surface loosens into small yellow-green beads instead of staying tight and dark. If a heat wave lands while heads are sizing, extra water and a bit of afternoon shade cloth buy a few days of protection until the weather breaks, which is often enough to save the crop given how the lake tends to knock summer heat back down within a week or so.
Clay ground east, sand ground west, and the disease that follows clay
Southeast Michigan's soil, built from an old glacial lakebed, runs heavy and holds water; southwest Michigan's fruit belt soil, built from windblown lake sand, drains almost too fast. Broccoli on clay ground is the one at real risk for clubroot, a soil fungus that swells and distorts roots until the plant wilts in full sun even with wet soil underneath, because the roots can no longer move water properly. Pull a stunted plant and find lumpy, clublike roots instead of clean white ones, and that is the diagnosis.
There is no cure once clubroot is in the ground, so prevention is the whole plan on clay soil: keep pH at 7.0 or a touch above, since the fungus loses its grip in that range, and give brassicas a full 3 years before planting them back in the same bed. Raised beds filled with amended soil sidestep the problem entirely on the heaviest clay lots, and drainage alone, keeping the root zone from sitting wet, cuts the risk even before you touch the pH.
Loopers hide, so check both sides of the leaf
Cabbage loopers are the sneaky one of Michigan's brassica pests because they are pale green and match the leaf almost exactly, and they feed mostly from the underside where a quick glance never catches them. The tell is the damage pattern: ragged, irregular holes between the veins rather than the neat round holes flea beetles leave. Check the undersides of a handful of leaves once a week starting as soon as heads begin to form, since that is when losing leaf area costs the most yield.
Bt kurstaki sprayed on the leaf undersides, reapplied after rain, kills loopers and imported cabbageworms without touching the bees and predatory beetles working the rest of the garden, and it works best started early rather than after a plant is already skeletonized. Floating row cover from transplant until heads begin to show is the simpler option for a small planting: it blocks the egg-laying moths completely and only has to come off once heads need pollinator-free space to finish sizing, which they do on their own from there.
In Michigan: watch for
The pests that find broccoli here.
A middle-length season, about 156 frost-free days, means broccoli overlaps cabbage worms & loopers for a stretch each summer. Check plants every week or two and treat early.
Green caterpillars chewing ragged holes; green droppings.
Organic fix: Handpick, cover with netting, spray Bt.
Gray-green clusters tucked into the leaf folds.
Organic fix: Blast with water, then insecticidal soap.
Tiny holes peppering the young leaves.
Organic fix: Row cover from day one; diatomaceous earth.
Black rot
Yellow V-shaped wedges cutting in from the leaf edge, veins blackening inside.
Organic fix: Pull infected plants, water at the base, keep brassicas out of that bed 3 years.
Seedlings wilt, yellow and stall for no reason; white maggots tunnel the roots.
Organic fix: Row cover before the flies are up, when yellow rocket blooms; rotate the bed.
Your season math: Michigan gives broccoli about 156 frost-free days, and it needs roughly 60 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting broccoli in Michigan: questions
When should I plant broccoli in Michigan?+
In a typical Michigan year, sow broccoli or set out transplants between Mar 14 to Apr 11, keyed to the state's median last frost around May 5. There's also a fall window: Jun 24 to Aug 3. Your exact dates shift with your ZIP code and microclimate.
When do I start broccoli seeds indoors in Michigan?+
Start seeds inside about 6 weeks before set-out: roughly Jan 31 to Feb 28 for a typical Michigan season.
What USDA zone is Michigan?+
Michigan spans zones 4b–6b, mostly zone 6. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many broccoli plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.