Climate Zones & Hardiness¶

Kamerplanter determines how winter-hardy your site is automatically from your GPS coordinates — you don't have to look up which zone you're in yourself. This zone feeds the hardiness traffic light for your perennial plants (see Overwintering) and helps you see whether a species will survive at your site without extra protection.

What Are Hardiness Zones?¶

Hardiness zones (following the scheme of the U.S. Department of Agriculture (USDA)) classify locations by their mean annual minimum temperature (averaged over roughly 30 years) into zones 1–13. Each zone is further split into two half-zones, a and b (e.g. 7a, 8b), each spanning roughly 2.8 °C. The lower the zone number, the colder the location in winter.

For Germany, Austria, and Switzerland, zones 5a to 9a are the most relevant: alpine and highland elevations tend to sit at 5a–6a, the common lowlands at 6b–7b, and the mildest special locations (Rhine valley, Lake Constance, Ticino) reach 8a to 9a.

This zone scheme ties several things together in Kamerplanter: the structured hardiness zone field of a site (automatically derived or manually set), a species' hardiness rating in master data, and its four-level frost sensitivity rating (from "sensitive" to "very hardy"). The former free-text Climate zone field on a site (see Locations & Substrates) remains for compatibility — Kamerplanter automatically keeps it in sync with the derived or manually set zone.

How the Zone Is Determined¶

flowchart LR
    G["Site GPS<br/>coordinates"] --> N["Climate normals<br/>(NASA POWER)"]
    N --> R["Zone derivation<br/>(USDA schema)"]
    R --> Z["Site zone<br/>e.g. 7a"]
    Z --> V["Comparison with<br/>species hardiness"]
    V --> A["Hardiness traffic light<br/>green / yellow / red"]

For locations in Germany, Austria, and Switzerland, Kamerplanter does not use a ready-made map — a freely licensed DACH hardiness zone map does not exist. Instead, Kamerplanter calculates the zone itself: from the coldest monthly mean minimum temperature of your site's long-term climate normals, classified into one of 26 USDA half-zones (1a–13b) using a fixed, license-free temperature-band schema — no proprietary USDA/PHZM/PRISM map data is used.

• Automatic background computation: Once GPS coordinates are set for your outdoor or greenhouse site and at least one usable climate-normal record is available, a quarterly background task (on the 1^st of January, April, July, and October) recomputes the zone automatically — with no action needed from you, just like the climate normals themselves.
• Manual override: You can override the derived zone by hand at any time — for example, if your site has a known microclimate (courtyard, south-facing slope). A manually set zone is never overwritten again by the automatic refresh. This currently only works via the API — a control for it in the site form doesn't exist yet (see For Technical Users / Self-Hosters below).
• Traceability: For every derived zone, Kamerplanter stores where it came from (automatically derived from GPS coordinates or manually set) and when it was last computed — also currently only retrievable via the API, not yet shown in the site form.
• GPS only, no postal code: Derivation currently works exclusively from GPS coordinates; postal-code-based derivation is not (yet) implemented.

The Hardiness Traffic Light¶

The hardiness traffic light (see Overwintering) compares a species' hardiness rating with the hardiness zone of its site. It prefers the structured, automatically derived zone; if no zone has been computed yet for a site, it falls back to the free text in the Climate zone field.

Kamerplanter checks the following rules in order — the first one that matches decides the traffic light:

Example: A fig tree that, according to master data, needs at least zone 8a, at a site in zone 7a — the site zone is exactly one zone colder than the minimum required → yellow or red rating, depending on whether the specific cultivar is itself rated frost-sensitive.

Frost Reference Dates for the Sowing Calendar¶

Every zone catalog entry carries typical dates for the last and first frost. As long as you haven't set your own frost dates or a weather API connection for your site, Kamerplanter automatically prefills these reference values into the frost date fields of your Sowing Calendar — once your site's hardiness zone has been derived at least once.

For Technical Users / Self-Hosters¶

Fetching the Global Zone Catalog¶

curl -H "Authorization: Bearer <JWT>" \
  http://localhost:8000/api/v1/hardiness-zones | python3 -m json.tool

Reading a Site's Hardiness Zone¶

curl -H "Authorization: Bearer <JWT>" \
  http://localhost:8000/api/v1/t/<tenant-slug>/sites/<site_key>/hardiness | python3 -m json.tool

Re-Deriving or Manually Setting a Zone Immediately¶

Instead of waiting for the next quarterly background run, you can trigger the derivation for a site immediately — provided climate normals already exist for it:

curl -X POST -H "Authorization: Bearer <JWT>" \
  "http://localhost:8000/api/v1/t/<tenant-slug>/sites/<site_key>/resolve-hardiness-zone"

An already manually set zone is left untouched unless you force the re-derivation with ?force=true. To set a zone manually (and permanently protect it from the automatic refresh), use the regular site update and pass hardiness_zone in the request body — see Environment Variables — Hardiness Zones and API Reference — Hardiness Zones for details.

Frequently Asked Questions¶

See Also¶

• Locations & Substrates
• Weather Sources per Location — Climate at the Site
• Overwintering
• Growth Phases
• Calendar & Sowing Calendar
• API Reference — Hardiness Zones
• Environment Variables — Hardiness Zones