Seed Starting Date Calculator

Finding your real frost date

The schedule is only as honest as the frost date you enter. Use the average last spring frost from your extension office or a climate normal — not last year’s lucky early thaw. Averages still carry about a 50% chance of a later frost, so harden seedlings off and keep row cover handy. Change the date above and the whole 50-crop table recalculates: indoor starts = frost minus weeks×7 days; transplant and direct sow = frost plus (or minus) their week offsets from our crop data file.

Worked check with April 15 frost: tomatoes start indoors about March 4 (six weeks before), transplant about April 29 (two weeks after), and peas direct sow about February 18 (eight weeks before). Those dates print as “Mar 4” style month names — locale-safe, no ambiguous numeric slashes.

Reading the master table

The table is the centerpiece. Sort is chronological by the earliest action for each crop so you can scan “what’s next.” A dash means that step does not apply (for example, direct-sow-only peas skip indoor starts). Fall-planted garlic is flagged in notes because it keys off first fall freeze, not spring last frost. On phones, swipe the table horizontally — columns stay aligned for print/PDF too.

Crops that hate transplanting

Root crops and many legumes prefer direct sowing. Our data marks direct-sow-only crops so you do not waste indoor tray space. Cucurbits can be started indoors briefly, but they sulk if pot-bound — time those starts late and transplant carefully. If a packet says “do not transplant,” trust the packet even when the table shows an indoor column for a related crop.

Hardening off

Transplant dates assume you will harden seedlings for about a week: increasing outdoor time, wind, and cooler nights. Skipping that step burns leaves and stalls growth even when the calendar says “go.” Water trays before a cold night; bring them in if a hard freeze is forecast after your average date.

Fall garden countdown

This tool is spring-anchored. For fall crops, count backward from your first fall frost using days to maturity plus a buffer — a topic for succession planning alongside the spacing calculator. In nearly frost-free zones, treat “last frost” as the start of your main warm-season window and still stagger plantings to beat heat, not ice. Keep a separate fall list taped beside this spring table so July does not erase September sowings from your mind.

Common mistakes: starting tomatoes ten weeks early under weak light (leggy junk), sowing peas in cold mud without drainage, and treating the table as a guarantee instead of a plan you adjust with the weekly forecast. Print the schedule, tape it in the shed, and cross off rows as you sow. If your microclimate is a frost pocket, shift the frost date later by a week and regenerate the table rather than gambling on the county average alone.

Frequently asked questions