Hardiness Ratings
All ratings refer to the UK growing conditions unless otherwise
stated. Minimum temperature ranges (in degrees C) are shown in
brackets
- H1A:
under glass all year (>15C)
- H1B:
can be grown outside in the summer (10 - 15)
- H1C:
can be grown outside in the summer (5 - 10)
- H2:
tolerant of low temperatures, but not surviving being frozen (1 to 5)
- H3:
hardy in coastal and relatively mild parts of the UK (-5 to 1)
- H4:
hardy through most of the UK (-10 to -5)
- H5:
hardy in most places throughout the UK even in severe winters (-15 to -10)
- H6:
hardy in all of UK and northern Europe (-20 to -15)
- H7:
hardy in the severest European continental climates (< -20)