{
  "name": "RHS Hardiness Ratings — H1a to H7 scale with °C bands",
  "description": "Open reference table of the Royal Horticultural Society plant hardiness scale (H1a, H1b, H1c, H2, H3, H4, H5, H6, H7): the minimum temperature each band tolerates in °C and what it means for growing the plant outdoors in the UK. Free CSV + JSON, CC-BY 4.0.",
  "url": "https://www.getgrowli.app/data/uk-rhs-ratings",
  "license": "https://creativecommons.org/licenses/by/4.0/",
  "creditText": "RHS hardiness-rating reference table compiled by Growli (getgrowli.app), CC-BY 4.0, from the Royal Horticultural Society plant-hardiness rating scale.",
  "sources": [
    "Royal Horticultural Society — plant hardiness ratings (rhs.org.uk)"
  ],
  "methodology": "Ratings and temperature bands reproduce the published RHS plant-hardiness rating scale, verified May 2026 against the official RHS hardiness-rating document. The \"what it means\" column is a plain-language gloss of each band for UK growers; it adds no temperatures the RHS scale does not define.",
  "spatialCoverage": "GB",
  "lastVerified": "2026-05-15",
  "recordCount": 9,
  "data": [
    {
      "rating": "H1a",
      "minTempC": "above about 15 °C (warm, never cold)",
      "meaning": "Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever."
    },
    {
      "rating": "H1b",
      "minTempC": "about 10 °C (sustained cold below this is damaging)",
      "meaning": "Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season."
    },
    {
      "rating": "H1c",
      "minTempC": "about 5 °C (and never frost)",
      "meaning": "Warm-temperate — can summer outdoors but must come in well before the first frost."
    },
    {
      "rating": "H2",
      "minTempC": "about 1 to 5 °C — tolerates cold but no real frost",
      "meaning": "Tender — survives a frost-free greenhouse or a very mild, sheltered spot."
    },
    {
      "rating": "H3",
      "minTempC": "about −5 to 1 °C — a light, short frost only",
      "meaning": "Half-hardy — comes through mild UK winters outside but is killed by a hard freeze."
    },
    {
      "rating": "H4",
      "minTempC": "about −10 to −5 °C",
      "meaning": "Hardy in an average winter across much of the temperate world."
    },
    {
      "rating": "H5",
      "minTempC": "about −15 to −10 °C",
      "meaning": "Hardy in most of the UK and in cold winters."
    },
    {
      "rating": "H6",
      "minTempC": "about −20 to −15 °C",
      "meaning": "Hardy throughout the UK and northern Europe."
    },
    {
      "rating": "H7",
      "minTempC": "below about −20 °C",
      "meaning": "Hardy in the severest European continental winters."
    }
  ]
}