GrowZone

Crop by USDA zone

When to plant tomatoes in zone 6a

In USDA zone 6a, plant tomatoes around May 12, after the representative last frost near May 5. Start seeds indoors around Mar 24.

This page summarizes the supported ZIPs in zone 6a. Your exact city can move earlier or later, so use the ZIP lookup for the frost-station-specific answer.

Get exact tomatoes dates by ZIP code.

Seed starting schedule

Tomatoes dates for Denver, CO

StepDateHow to use it
Start IndoorsMarch 24, 2026Start seeds under lights or in a bright indoor seed-starting space.
Transplant OutdoorsMay 12, 2026Move hardened-off seedlings outside after the frost-risk window.
Milwaukee, WI · Zone 6a Tomatoes May 17 Open ZIP-specific answer · last frost May 10 Chicago, IL · Zone 6a Tomatoes May 2 Open ZIP-specific answer · last frost Apr 25 Omaha, NE · Zone 6a Tomatoes May 12 Open ZIP-specific answer · last frost May 5 Aurora, CO · Zone 6a Tomatoes May 12 Open ZIP-specific answer · last frost May 5 Denver, CO · Zone 6a Tomatoes May 12 Open ZIP-specific answer · last frost May 5 Colorado Springs, CO · Zone 6a Tomatoes May 22 Open ZIP-specific answer · last frost May 15