To qualify for an Award of Garden Merit, a plant • must be available horticulturally • must be of outstanding excellence for garden decoration or use • must be of good constitution • must not require highly specialist growing conditions or care • must not be particularly susceptible to any pest or disease • must not be subject to an unreasonable degree of
reversion. The "Award of Garden Merit"
symbol represents a cup-shaped
trophy with handles. It is cited together with a
hardiness rating as follows: •
H1 Requires a heated glasshouse •
H1a Warmer than 15°C/59°F: tropical plants for indoors and heated greenhouses •
H1b 10°C/50°F to 15°C/59°F: subtropical plants for indoors and heated greenhouses •
H1c 5°C/41°F to 10°C/50°F: warm temperate plants that can go outdoors in summer •
H2 1°C/34°F to 5°C/41°F: plants that need a frost-free greenhouse in winter •
H3 −5°C/23°F to 1°C/34°F: hardy outside in some regions or situations, or which - while usually grown outside in summer - need frost protection in winter (e.g. dahlias) •
H4 −10°C/14°F to −5°C/23°F: plants hardy outside in most of the UK in an average winter •
H5 −15°C/5°F to −10°C/14°F: plants hardy outside in most of the UK in severe winters •
H6 −20°C/−4°F to −15°C/5°F: plants hardy outside in the UK and northern Europe •
H7 Colder than −20°C/−4°F: plants hardy outside in the severest European climates '' 'Perle von Nürnberg', a winner of the Award of Garden merit ==See also==