When should I start seeds indoors by zone?

Use the USDA zone as a planning shortcut, then check the ZIP-specific last frost. In zone 8a, the representative tomato seed-start date is around Feb 15 for ZIP 30301.

Why can a ZIP seed-starting date differ from a zone chart?

A USDA zone describes winter cold risk. Seed-starting dates depend on local last frost, crop transplant age, and whether the crop should be direct-sown.

Should every crop be started indoors?

No. Tomatoes and peppers are usually started indoors, while beans, radishes, spinach, and cilantro are often direct-sown in the GrowZone crop rules.

GrowZone guide

Starting seeds indoors by zone

Start with your USDA zone for a rough seed-starting window, then use your ZIP code for the actual frost-station estimate.

GrowZone Editorial · Last updated June 28, 2026

In zone 8a, the representative GrowZone tomato seed-start date is around Feb 15. ZIP 30301 uses the Atlanta frost station and a Mar 29 last-frost estimate.

Source: atlanta-hartsfield frost station, USDA zone 8a, last updated 2026-06-28. Verify locally before planting high-value crops because microclimates, current weather, and yard exposure can move the safe date.

Seed-starting matrix by crop and USDA zone

The table uses one representative supported ZIP per zone. Open a crop-by-zone page for broad planning, then enter your ZIP for the frost-station-specific date.

Crop	Zone 10a	Zone 10b	Zone 11a	Zone 12b	Zone 5a	Zone 6a	Zone 6b	Zone 7a	Zone 7b	Zone 8a	Zone 8b	Zone 9a	Zone 9b
Tomatoes	Dec 21, 6 weeks before frost	Dec 9, 6 weeks before frost	Nov 20, 6 weeks before frost	Nov 20, 6 weeks before frost	Mar 29, 6 weeks before frost	Mar 24, 6 weeks before frost	Mar 19, 6 weeks before frost	Mar 9, 6 weeks before frost	Feb 27, 6 weeks before frost	Feb 22, 6 weeks before frost	Jan 29, 6 weeks before frost	Jan 18, 6 weeks before frost	Jan 9, 6 weeks before frost
Peppers	Dec 7, 8 weeks before frost	Nov 25, 8 weeks before frost	Nov 6, 8 weeks before frost	Nov 6, 8 weeks before frost	Mar 15, 8 weeks before frost	Mar 10, 8 weeks before frost	Mar 5, 8 weeks before frost	Feb 23, 8 weeks before frost	Feb 13, 8 weeks before frost	Feb 8, 8 weeks before frost	Jan 15, 8 weeks before frost	Jan 4, 8 weeks before frost	Dec 26, 8 weeks before frost
Basil	Dec 28, 5 weeks before frost	Dec 16, 5 weeks before frost	Nov 27, 5 weeks before frost	Nov 27, 5 weeks before frost	Apr 5, 5 weeks before frost	Mar 31, 5 weeks before frost	Mar 26, 5 weeks before frost	Mar 16, 5 weeks before frost	Mar 6, 5 weeks before frost	Mar 1, 5 weeks before frost	Feb 5, 5 weeks before frost	Jan 25, 5 weeks before frost	Jan 16, 5 weeks before frost
Carrots	Direct sow Jan 11	Direct sow Dec 30	Direct sow Dec 11	Direct sow Dec 11	Direct sow Apr 19	Direct sow Apr 14	Direct sow Apr 9	Direct sow Mar 30	Direct sow Mar 20	Direct sow Mar 15	Direct sow Feb 19	Direct sow Feb 8	Direct sow Jan 30
Lettuce	Jan 4, 4 weeks before frost	Dec 23, 4 weeks before frost	Dec 4, 4 weeks before frost	Dec 4, 4 weeks before frost	Apr 12, 4 weeks before frost	Apr 7, 4 weeks before frost	Apr 2, 4 weeks before frost	Mar 23, 4 weeks before frost	Mar 13, 4 weeks before frost	Mar 8, 4 weeks before frost	Feb 12, 4 weeks before frost	Feb 1, 4 weeks before frost	Jan 23, 4 weeks before frost
Cucumbers	Jan 11, 3 weeks before frost	Dec 30, 3 weeks before frost	Dec 11, 3 weeks before frost	Dec 11, 3 weeks before frost	Apr 19, 3 weeks before frost	Apr 14, 3 weeks before frost	Apr 9, 3 weeks before frost	Mar 30, 3 weeks before frost	Mar 20, 3 weeks before frost	Mar 15, 3 weeks before frost	Feb 19, 3 weeks before frost	Feb 8, 3 weeks before frost	Jan 30, 3 weeks before frost
Zucchini	Jan 11, 3 weeks before frost	Dec 30, 3 weeks before frost	Dec 11, 3 weeks before frost	Dec 11, 3 weeks before frost	Apr 19, 3 weeks before frost	Apr 14, 3 weeks before frost	Apr 9, 3 weeks before frost	Mar 30, 3 weeks before frost	Mar 20, 3 weeks before frost	Mar 15, 3 weeks before frost	Feb 19, 3 weeks before frost	Feb 8, 3 weeks before frost	Jan 30, 3 weeks before frost
Cilantro	Direct sow Jan 18	Direct sow Jan 6	Direct sow Dec 18	Direct sow Dec 18	Direct sow Apr 26	Direct sow Apr 21	Direct sow Apr 16	Direct sow Apr 6	Direct sow Mar 27	Direct sow Mar 22	Direct sow Feb 26	Direct sow Feb 15	Direct sow Feb 6
Bush beans	Direct sow Feb 8	Direct sow Jan 27	Direct sow Jan 8	Direct sow Jan 8	Direct sow May 17	Direct sow May 12	Direct sow May 7	Direct sow Apr 27	Direct sow Apr 17	Direct sow Apr 12	Direct sow Mar 19	Direct sow Mar 8	Direct sow Feb 27
Spinach	Direct sow Jan 4	Direct sow Dec 23	Direct sow Dec 4	Direct sow Dec 4	Direct sow Apr 12	Direct sow Apr 7	Direct sow Apr 2	Direct sow Mar 23	Direct sow Mar 13	Direct sow Mar 8	Direct sow Feb 12	Direct sow Feb 1	Direct sow Jan 23
Radishes	Direct sow Jan 4	Direct sow Dec 23	Direct sow Dec 4	Direct sow Dec 4	Direct sow Apr 12	Direct sow Apr 7	Direct sow Apr 2	Direct sow Mar 23	Direct sow Mar 13	Direct sow Mar 8	Direct sow Feb 12	Direct sow Feb 1	Direct sow Jan 23
Kale	Dec 28, 5 weeks before frost	Dec 16, 5 weeks before frost	Nov 27, 5 weeks before frost	Nov 27, 5 weeks before frost	Apr 5, 5 weeks before frost	Mar 31, 5 weeks before frost	Mar 26, 5 weeks before frost	Mar 16, 5 weeks before frost	Mar 6, 5 weeks before frost	Mar 1, 5 weeks before frost	Feb 5, 5 weeks before frost	Jan 25, 5 weeks before frost	Jan 16, 5 weeks before frost
Watermelon	Jan 11, 3 weeks before frost	Dec 30, 3 weeks before frost	Dec 11, 3 weeks before frost	Dec 11, 3 weeks before frost	Apr 19, 3 weeks before frost	Apr 14, 3 weeks before frost	Apr 9, 3 weeks before frost	Mar 30, 3 weeks before frost	Mar 20, 3 weeks before frost	Mar 15, 3 weeks before frost	Feb 19, 3 weeks before frost	Feb 8, 3 weeks before frost	Jan 30, 3 weeks before frost

Zone 8a example

For a representative zone 8a calendar, tomatoes start indoors Feb 15, peppers start indoors Feb 8, and basil starts indoors Mar 1. These are planning dates, not guarantees.

Open the ZIP and crop seed-starting calculator