About

Semiterra started from a simple observation: a national sowing calendar is of little use when you garden in the Alps. Tomatoes are not sown at the same time in Marseille, in Paris and at 1,000 metres.

Dates computed for your town

For every town in France, Belgium, Switzerland, Luxembourg, Germany, Austria and Ireland, Semiterra computes the average dates of the last spring frost and the first autumn frost from the daily records of thousands of stations of the national weather services over 1991-2020, corrected for the altitude of your town. Growing calendars are expressed relative to these frost dates, so they shift automatically with where you garden.

Semiterra also takes summer heat into account: where it is strong, heat-sensitive crops (lettuce, spinach, peas…) are not offered for sowing if they would mature in the middle of a heatwave; where summers are cool, demanding crops (melon, aubergine, pepper…) are flagged “Under cover advised”. The full list of data sources is given in our legal notice.

Cited sources

Calendars, growing data and companion planting come from recognised sources — seed companies, the Royal Horticultural Society, university extension services, reference gardening books and websites — cited on each plant page. For companion planting, we honestly show the level of evidence: scientific study, extension-service recommendation or mere tradition.

A blog written with the help of AI, reviewed by humans

Every week, an article covers what to do in the vegetable garden at that time of year. It is written with the help of artificial intelligence from Semiterra's data, then reviewed by our team before publication.

Who we are

Semiterra is published by Veltone SAS, a small company based in the French Alps. A question, a suggestion, an error to report? Write to us: contact@semiterra.com.