GrowZone

Crop by USDA zone

When to plant basil in zone 6a

In USDA zone 6a, plant basil around May 15, after the representative last frost near May 5. Start seeds indoors around Mar 31.

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 basil dates by ZIP code.

Seed starting schedule

Basil dates for Denver, CO

StepDateHow to use it
Start IndoorsMarch 31, 2026Start seeds under lights or in a bright indoor seed-starting space.
Transplant OutdoorsMay 15, 2026Move hardened-off seedlings outside after the frost-risk window.
Direct SowMay 15, 2026Sow seed outside when the crop and soil can handle the window.
Milwaukee, WI · Zone 6a Basil May 20 Open ZIP-specific answer · last frost May 10 Chicago, IL · Zone 6a Basil May 5 Open ZIP-specific answer · last frost Apr 25 Omaha, NE · Zone 6a Basil May 15 Open ZIP-specific answer · last frost May 5 Aurora, CO · Zone 6a Basil May 15 Open ZIP-specific answer · last frost May 5 Denver, CO · Zone 6a Basil May 15 Open ZIP-specific answer · last frost May 5 Colorado Springs, CO · Zone 6a Basil May 25 Open ZIP-specific answer · last frost May 15