When to start seeds indoors

Seed-starting timing is always relative to an anchor. For most crops that anchor is your average last spring frost; for others it is the date you plan to transplant. Once you have the anchor, you count backwards by the crop’s recommended head start.

A crop that wants six weeks indoors before last frost gets sown 42 days earlier. That is all the math is — but doing it by hand across a dozen crops is exactly where mistakes creep in.

The transplant date in your plan assumes hardened-off plants. Give seedlings seven to ten days of gradual outdoor exposure before they go in the ground, and never rush frost-tender crops out early to hit a date on a spreadsheet.

Some crops resent transplanting or simply grow fast enough that direct sowing wins. The calculator shows a crop’s direct-sow rule alongside its indoor-start timing so you can choose deliberately rather than by habit.