When to Plant Tomatoes in Zones 5-6 (2026)

Tomatoes are a heat-loving crop that cannot go in the ground until the danger of frost has passed. In zones 5-6, that means starting seeds indoors well before your last outdoor planting date, then waiting for both the calendar and the soil temperature to cooperate.

The two dates that matter

University of Minnesota Extension’s guide to growing tomatoes gives a simple rule: start seeds indoors five to six weeks before you plan to plant outside, and do not transplant outdoors until all danger of frost has passed and the soil has warmed.

In zone 5-6, the average last spring frost typically falls somewhere in the second half of April to mid-May, depending on exactly where you are in the band. Use your own average last-frost date, not a zone-wide guess, in the planting calendar calculator below — it does the date math for you from the same five-to-six-week rule.

Worked example

Suppose your average last frost date is May 10.

• Start seeds indoors: five to six weeks before transplanting, so around March 29 to April 5.
• Transplant outdoors: after all danger of frost has passed and the soil has warmed — for most zone 5-6 gardens, that is on or shortly after May 10, once nights are reliably above freezing.

This is arithmetic from the rule above, not a separate source — check your own last frost date if it differs from this example.

Before you transplant, check off