Seed Starting Calculator

Days to Germinate and Days to Harvest are fixed values this calculator looks up for each Plant Type from typical seed-starting data, so switching plants changes how long each stage takes. Last Frost Date, by contrast, only shifts where that fixed-length schedule sits on the calendar -- it doesn't change how many days apart your start, transplant, and harvest dates are from each other.

Cold-hardy plants like lettuce and broccoli can tolerate light frost and are typically transplanted a couple of weeks before your last frost date to take advantage of cool spring weather, while tender, frost-sensitive plants like tomatoes, peppers, and melons must wait until after the last frost to avoid being killed by a late cold snap. This calculator encodes that difference as a per-plant offset applied to your Last Frost Date.

No -- Weeks to Start Indoors only moves your Start Seeds Indoors date earlier (further back from your last frost date) and shortens Total Growing Days; it doesn't change your Transplant Outdoors or Expected Harvest dates, since those are fixed relative to your last frost date and plant type, not to when you started seeds indoors.

The default day-of-year values (like day 120 for April 30) are just examples -- your actual average last frost date depends on your specific location and USDA hardiness zone, and it can vary meaningfully year to year. Check your local extension office or a USDA hardiness zone map for your area's typical last frost date before relying on this schedule.

It uses fixed, typical timings by plant type and doesn't account for your specific variety within that plant type, indoor growing conditions like light and temperature, soil quality, or unusual weather in a given year -- all of which can shift germination, transplant readiness, and harvest timing earlier or later than these general estimates.