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All ratings refer to the UK growing conditions unless otherwise stated. Minimum
temperature ranges (in degrees C) are shown in brackets
AGM plants have been through a rigorous trial and assessment programme. They are:
This plant will provide nectar and pollen for bees and the many other types of pollinating insects.
It is included in an evolving list of plants carefully researched and chosen by RHS experts. Divided into 3 groups these lists, linked below, are maintained by a team of RHS staff and are reviewed annually.
'Blue Eclipse' is a medium-sized deciduous climber, up to 3 metres high, with divided green leaves and large bell-like flowers of deep blue with a white edge on the outside and white inside, followed by fluffy seedheads
A. thomsonii is a clump-forming perennial, to 1m tall, with oval, toothed leaves, up to 10cm long, on hairy stems. Flowerheads, up to 5cm across, comprising lavender-blue rays and a central yellow disk, are held on slender branches from late summer into autumn
'Diana Clare' is a vigorous semi-evergreen perennial with narrow silvery-green leaves, lightly speckled with dark green near the margins, and violet-blue flowers from late winter to late spring
'Hensol Harebell' is an erect herbaceous perennial to 90cm, with divided leaves tinted purple in late summer, and nodding, rich violet-blue flowers 5cm wide, with short, hooked spurs
E. ritro is a robust, upright herbaceous perennial, with jaggedy-divided, prickly dark green leaves whitish beneath. Rounded, violet-blue flower heads on silvery, branched, leafy stems
'Cambridge Blue' is a compact annual to 15cm, forming a low hummock of narrow foliage, with clear light blue, two-lipped flowers 2cm across in summer and autumn
Opal is a semi-evergreen perennial with ovate leaves heavily blotched and speckled with silver; clear pale blue flowers open from pale pink buds in spring on stems to 35cm tall
'Leonora' is a clump-forming perennial, to 45cm tall, with lance-shaped foliage and, in summer, clusters of violet-blue, three-petalled flowers borne at the ends of the branching stems
'Père David' is a mat-forming plant to 15cm tall, with blue-green leaves and greenish-blue flowers in late spring and early summer
C. trachelium is a robust perennial with nettle-like, deeply toothed leaves and erect, leafy stems bearing a raceme of bell-shaped lavender-blue flowers 3cm long in summer
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