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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 Pearl' is a compact herbaceous perennial up to 30cm high with fresh green pinnate leaves and sky-blue flowers in early summer
Brise d'Anjou is a clump-forming perennial of upright growth, to 60cm tall, with the leaflets edged with cream, and small light blue flowers; grown for its foliage, and not vigorous, so the flowers are best removed
'Lambrook Mauve' makes a compact spreading mound of pinnate leaves, to 45cm in height, with small clusters of broadly bell-shaped lilac-blue flowers 2cm in width
'Purple Rain' is a herbaceous perennial producing a mound of foliage with very small leaflets in dark green flushed with purple-black. Star-shaped, purple flowers with prominent stamens and cream anthers appear in small clusters on dark stems in early summer
P. caeruleum subsp. caeruleum f. album is a vigorous upright perennial to 75cm tall, with light green, pinnate leaves and pure white flowers with yellow anthers
P. caeruleum is an erect perennial to 90cm tall, with ladder-like, pinnate leaves and stiff stems bearing sprays of blue flowers 2.5cm wide with prominent yellow stamens in early summer; often seeds about rather freely
'Apricot Delight' is a perennial forming a spreading clump of pinnate leaves, with upright stems to 40cm bearing loose clusters of bowl-shaped, pink flowers shading to apricot-yellow in the centre
Bressingham Purple is a herbaceous perennial with foliage that is purple-tinged in spring and autumn. It bears clusters of sky blue flowers, marked in a darker blue with a small white centre. These are cupped in shape and are held in clusters from late spring to midsummer
P. viscosum is a compact herbaceous perennial to 30cm tall with sticky, pinnate leaves up to 15cm long made up of many spoon-shaped leaflets and blue-purple flowers borne in late spring and early summer
'Scottish Garden' is a perennial to 80cm tall, with pinnate leaves divided into many narrowly lance-shaped leaflets, and compact sprays of open bell-shaped light violet-blueflowers throughout the summer
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