When to plant tomatoes in USDA Zone 5a

Plan your tomatoes planting around local frost risk and soil temperature, then work backward from the harvest week your buyers need. The calendar below is a starting point, not a field-level weather forecast.

Madison WI, Des Moines, southern MN, central MI. Average last spring frost May 8, first fall frost September 29 — a 144-day frost-free season.

Zone fit: good
Tomatoes is frost-tender, so timing the outdoor transplant to the last frost matters more here than in warmer zones. Row cover buys 2 weeks of head start.

Key dates

Start seeds indoors
March 20 – April 3
Transplant outdoors
May 15 – June 5
Expected first harvest
August 5 – September 2
Fall planting window
June 16 – July 7
Fall harvest window
September 6 – October 4

Windows are calculated from your zone's average frost dates. Adjust ±1 week for microclimates, elevation, and your own frost records.

Spacing and soil

Plant spacing
24″
Row spacing
48″
Seed depth
0.25″
Soil temperature
70–85°F
Frost tolerance
tender
Days to harvest
75 days

Grower notes for Zone 5a

Set transplants deep — bury two-thirds of the stem to encourage adventitious roots. Stake or cage before fruit set.

Plant near: basil, carrots, onions

Keep away from: brassicas, corn, fennel

Other nightshades for Zone 5a

Same crop, other zones

Track your own plantings

BAU Farm Intelligence turns these windows into per-field tasks — indoor seed-start reminders, transplant dates, harvest projections — using your farm's actual frost history.

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