Harvest Date & Sowing Planner

Planning Harvest Windows

Days to maturity (DTM) describes how long a crop typically takes to reach harvestable size, but the starting point depends on the crop and seed packet. Some packets count from direct seeding, some from transplanting, and some assume emergence after seedlings are visible. The crop preset gives a reasonable starting range, but the variety-specific number on your packet or plant tag should take priority.

This planner treats harvest start as the maturity date. The harvest-window length is inclusive: a 14-day window includes the maturity date as day 1 and ends 13 days later. That distinction matters when you are planning a market harvest, CSA box, or fall crop close to frost.

Frost risk is handled with editable first- and last-frost dates. The built-in city, ZIP-prefix, and USDA-zone estimates are broad planning shortcuts, not a weather forecast. Use local extension guidance, nearby weather-station normals, and your own garden records when the exact date matters.

Weather and soil temperature can shift real harvest dates. Cool spring soil can slow emergence, heat can shorten lettuce or radish quality windows, and stress can delay fruiting crops. Use the result as a calendar baseline, then adjust after observing the crop.

Formula and Method

Forward plan: maturity date = sowing or transplant date + DTM. Harvest start = maturity date. Inclusive harvest end = harvest start + harvest window - 1 day. Frost buffer = first frost date - harvest end.

Reverse plan: latest sowing or transplant date = target harvest start - DTM - safety buffer. With a safety buffer, the maturity date lands before the target harvest date so the crop has time to size up before the deadline. If the crop is set to transplant mode, the tool also suggests a transplant date and notes the typical nursery lead time from the crop preset.

Succession plan: each row adds the interval to the previous sowing date, then applies the same DTM and harvest-window calculation. Rows are marked Safe before frost, Tight window, After frost, or Already past based on the harvest date and frost buffer.

Calculation Examples

Direct-sown carrots: sow May 1, use 70 DTM, and choose a 21-day harvest window. The maturity and harvest-start date is July 10, and the inclusive harvest end is July 30.

Transplanted tomatoes: transplant May 15, use 75 DTM from transplant, and choose a 21-day harvest window. The first ripe harvest is around July 29, with a harvest window through August 18.

Fall lettuce reverse plan: target an October 1 harvest, use 45 DTM and a 10-day safety buffer. The latest sowing or transplanting date is August 7. If your first frost is October 10, the harvest window is tight and row cover may be useful.

FAQs

Where do I find days to maturity?

Use the seed packet, catalog listing, plant tag, or variety description. The preset ranges are starting points only.

Does DTM start from seed or transplant?

It depends on the packet. Direct-sown crops usually count from seeding or emergence. Tomatoes, peppers, and many brassicas often count from transplanting.

How do I calculate a fall planting date?

Use reverse mode with your target harvest or frost deadline, then subtract DTM and a safety buffer for slower fall growth.

What if harvest is after first frost?

Plant earlier, switch to a faster variety, harvest early, or use season extension. Frost-tender crops such as tomato, cucumber, squash, bean, and pepper are most at risk.

How much safety buffer should I add?

Seven days is a useful default. Use 10 to 14 days for cool soil, fall plantings, uncertain germination, or market dates that cannot slip.

How do I plan multiple harvests?

Use succession mode. Lettuce, radish, spinach, beans, and carrots often work well with 7- to 14-day sowing intervals.

Can I use this for containers or greenhouses?

Yes, but adjust the dates. Containers can warm and dry faster, while greenhouses, tunnels, and row covers can extend the season beyond outdoor frost dates.

Why include a harvest window?

Many crops are not harvested on one day. Here, a 14-day window includes the maturity date as day 1 and ends 13 days later.

Are results private?

Yes, everything runs locally in your browser.

Methodology and Sources

Last reviewed: June 29, 2026. Content review: Starlight Tools agriculture calculator editor.

Crop DTM presets are broad planning assumptions compiled from common seed-catalog ranges and extension-style vegetable planting guidance. Frost and season-length suggestions are estimated from USDA-zone style climate bands and common U.S. city examples; manual frost dates should override them for local planning.

Source basis: the USDA Plant Hardiness Zone Map defines hardiness zones from average annual extreme minimum temperature, and NOAA/NCEI U.S. Climate Normals provide official 30-year normals used for typical climate conditions. Frost estimates are planning averages, not forecasts.

Common Crop Timing Guide

Disclaimer

DTM values vary by cultivar and climate. Use local extension guidance and adjust for real field conditions.