# Sowing and Planting Calendar

> When to sow indoors, plant out, sow outside and harvest, from your own frost dates. Turns your last spring and first autumn frost dates into a sowing and planting calendar for up to 40 vegetables and herbs: indoor sowing, planting out, sowing outside with successive sowings, autumn planting and the harvest window, plus a calendar file with every date.

Part of usefulweb.site (https://usefulweb.site/). Part of [Hearth](https://hearth.usefulweb.site/) (ownerApp: hearth). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://hearthsowingcalendar.usefulweb.site/ (interactive tool at https://hearthsowingcalendar.usefulweb.site/tool)
- JSON API: POST https://hearthsowingcalendar.usefulweb.site/api/v1/calculate with a JSON object of inputs (schema: https://hearthsowingcalendar.usefulweb.site/api/v1/tool)
- OpenAPI: https://hearthsowingcalendar.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://hearthsowingcalendar.usefulweb.site/mcp - tool `hearth_sowing_calendar`

## Inputs
- crops (multiselect): Crops
- lastFrost (text, required): Last spring frost (MM-DD) - Month and day, for example 04-20. The Frost Dates Finder gives it for Germany and the United States.
- firstFrost (text, required): First autumn frost (MM-DD)
- year (integer): Season (year of the spring frost)

## Method
- Crop timings come from our crop table (40 vegetables and herbs, each cited to its RHS “Grow your own” page): weeks to sow indoors and to plant out or sow outside, counted from your last spring frost; garlic is planted around the first autumn frost.
- Tender crops (tomato, beans, courgette …) go out only after the last frost; half-hardy crops take a light frost; hardy crops (peas, broad beans, onions, carrots, cabbage) are sown or planted weeks before it.
- Successive sowings repeat every 2–3 weeks while the crop still ripens before frost: the last sowing is the first autumn frost minus the days to harvest, minus 14 more days for tender crops and plus 14 for hardy ones.
- Harvest starts at the first planting plus the days to harvest. Long-cropping plants (tomatoes, courgettes, kale, herbs …) are picked until the first autumn frost (tender), two weeks later (half-hardy) or six weeks later (hardy); others for three to six weeks after ripening.
- Calendar file: one all-day event per window start and per sowing, named after the task.

## Limits
- Timings are rules of thumb for temperate gardens. Soil temperature, variety and the weather of the year matter more than any calendar.