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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.
'Sky' is a herbaceous perennial 1.5m high with deciduous strap-shaped green leaves and flowerheads of long, tubular, sky-blue flowers, darker near the tips, which hang down as they open in late summer
'Lilac Time' is a clump-forming herbaceous perennial to 1m tall with strap-shaped foliage. Sturdy, upright stems bear dense heads of trumpet-shaped, pale lilac flowers in summer
'Snow Cloud' is an evergreen, clump-forming perennial with dark green foliage. Erect stems to 1.2m tall bear large, rounded heads of densely-clustered, narrow, white flowers in summer
'Hoyland Blue' is an evergreen, clump-forming perennial with broad, strap-shaped leaves. Rounded clusters of white to pale blue flowers with a darker stripe down the centre of each petal are borne on stems to 75cm tall from late summer into autumn
'Lilliput' is a compact herbaceous perennial to 45cm tall, with narrow leaves and erect stems bearing a rounded cluster of funnel-shaped dark blue flowers in late summer
'Black Pantha' is a semi-evergreen, clump-forming cultivar growing up to 1m tall. Deep blue-black flowers emerge from almost black buds in summer, forming flowerheads up to 20cm across held above the foliage on erect stems
'Angela' is a vigorous herbaceous perennial to 1.2m tall with strap-shaped leaves; in summer, heads of slightly nodding, pale blue, funnel-shaped flowers are borne on strong stems
'Marjorie' is a clump-forming perennial with deciduous, strap-like leaves and umbels of pale violet-blue flowers borne on stems to 1m tall in summer
Brilliant Blue is a relatively compact herbaceous perennial, growing to about 50cm tall, with clumps of strap-shaped green leaves. This cultivar flowers freely in the summer producing loose clusters of rich sky-blue flowers with a darker stripe running through each petal
'Bridal Bouquet' is a compact, clump-forming perennial with semi-evergreen, strap-shaped leaves. Open heads of white, trumpet-shaped flowers are borne on erect stems to 60cm tall in summer
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We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.