Groteket

A seed packet says the same thing to the whole country. Sow in March to April, plant out once the frost risk has passed. The advice is true and almost useless, because what separates the south of Sweden from the north is not a nuance but several weeks.

Growing zones do not help either, because they answer a different question. A zone tells you what survives the winter. It says nothing about which day you can sow.

That leaves the grower with a guess. Sow too early and the frost takes the seedlings. Sow too late and they never get to flower. The question is simple, and the answer was already sitting in open data.

The claim that could be wrong: the day you can sow can be computed for every municipality in the country, from data that is already published.

If that held, the problem was never a lack of knowledge. It was that nobody had done the arithmetic and put it where people actually look.

The basis is SMHI's 1991 to 2020 climate normals: the vegetation period, meaning the days with a mean temperature above five degrees, and the daily minimum temperatures that give the frost dates.

Each municipality is tied to its nearest usable weather station. 260 measurement series out of 702 stations, and half the country's municipalities sit within 14 kilometres of theirs. Elevation is corrected separately: the season shrinks by 5.7 days per hundred metres upward, measured across 242 station pairs.

Then the place meets the species. Germination time, time under cover, flowering period and frost tolerance decide where in the season the window may sit, and the window closes where the species can no longer manage thirty days of flowering before the season ends.

The easy way to set a frost date is to average thirty years. That gives a date which holds about half the time, which in practice means losing the seedlings every other year.

Groteket sets the date where nine years in ten have already had their last frost night. The advice lands a few days later and is worth considerably more, because a statement about when it is safe to sow has to be safe.

How that arithmetic works is stated openly on the site's method page. A tool that tells someone to put seeds in the ground on a given day owes them the reason.

You pick your municipality once and it follows you. Every species has its own page with its window, its growing guide and its varieties, and the lists can be read month by month: what can be sown now, what is flowering now.

Beyond the species there are pages on what goes wrong, from pests to diseases. And anyone who wants to can be told when the window opens in their own municipality, instead of keeping count themselves.

Groteket is the lab's model in a single build. The observation came out of real growing, the definition became a claim that could be tested, and the build became something that runs and can disappoint you.

The distribution link shows too: Groteket is published by Formise AB and marketed by Memorise. Build in the lab, distribute through the agency's client network. How the two fit together is under About, and the steps are on the process page.

Groteket stays in the lab for now. It is a build in production, not a company, and it should stay that way until there is a reason for anything else.