Be aware of the hardiness zone in your area before you decide to buy plants. Some plants might not survive over winter!

Based on the minimum ten-year average winter temperatures, plant hardiness zone maps have been progressively developed, first by the Department of Agriculture (USDA) for the United States and then more or less applied to the rest of the planet. The purpose of these hardiness zones is to identify how well plants will withstand the cold winter temperatures of these zones. But keep in mind that these maps are mostly guidelines as they do not factor in any potential micro climates, precipitation, humidity, summer heat tolerance, etc.

Selecting plants suited to the diverse English climate will be a key step to success. If you know your hardiness zone, find the best plants or exciting garden ideas for your geographic area.

If you are not sure which hardiness zone you belong to, please check the map below.

Hardiness Zones in the United Kingdom

  • The United Kingdom lies in USDA Plant Hardiness Zones 6 through 9 with some variations across regions and seasons. It enjoys a temperate maritime climate characterized by cool winters and warm summers. Summers are cooler than those on the continent (not much higher than 32ºC in summer), but the winters are milder (not much lower than 0ºC in winter). Around the coasts, February is normally the coldest month, but inland there is little to choose between January and February as the coldest month.
  • The frost free growing season is fairly long with the last frost dates ranging from March to April and the first frost dates starting as early as October until the end of November.
RHS Rating Temperature Hardiness USDA Zones Find Plants or Garden Ideas
H1a > 59ºF
  15ºC
Tropical 13 To be grown under glass or as a house plant
H1b 50ºF to 59ºF
10ºC to 15ºC
Subtropical 12 Can be grown outdoors in summer in warm,
sunny and sheltered locations, but will generally perform indoors
H1c 41ºF to 50ºF
5ºC to 10ºC
Warm temperate 11 Can be grown outdoors in summer throughout most of the UK.
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H2 34ºF to 41ºF
1ºC to 5ºC
Tender cool 10 Tolerant of low temperatures, but will not survive being frozen.
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H3 23ºF to 24ºF
-5ºC to 1ºC
Half-hardy  9 Hardy in coastal/mild areas, except in hard winters.
Likely to be damaged or killed in cold winters, particularly with no snow cover or if potted.
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H4 14ºF to 23ºF
-10ºC to -5ºC
Hardy
Average winter
8,9 Hardy through most of the UK apart from inland valleys, at altitude and central/northerly locations.
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H5 5ºF to 14ºF
-15ºC to -10ºC
Hardy
Cold winter
7,8 Hardy in most places throughout the UK even in severe winters.
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H6 -4ºF to 5ºF
-20ºC to -15ºC
Hardy
Very cold winter
6,7 Hardy across the UK and northern Europe.
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