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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.
A. carmichaelii has an upright habit and leathery leaves. Dense panicles of large violet or blue flowers are produced in autumn
A. napellus is an upright tuberous perennial to 1.5m tall, with deeply divided, dark green leaves and tall spires of violet-blue, hooded flowers in mid and late summer
A. bulleyana is a herbaceous perennial producing spikes of funnel-shaped, pale to mid-blue flowers in late summer
A. caulescens subsp. angustifolius has stiffly erect to sub-erect, greyish, narrow (3cm or less wide) leaves, and rather small flowers with the perianth segments not flared or recurved
'Blue Imp' is a clump-forming perennial forming a compact mound of grass-like foliage; sturdy stems to 70cm tall bear rounded clusters of intense blue, trumpet-shaped flowers in midsummer
A. campanulatus is a vigorous, clump-forming herbaceous perennial, to 1m tall, with narrow, strap-like, greyish-green leaves and erect stems bearing umbels of trumpet-shaped, pale to dark lavender-blue flowers in summer
A. caulescens is a deciduous species and reasonably hardy. The leaves are produced on a distinct stem, the basal sheathing leaves sometimes very short giving this part of the plant a leek-like appearance. Foliage is 25-60cm long, with flower stems 60-180cm. The number of flowers in a flowerhead is variable; the flowers are usually dark violet-blue, paler towards the base and with darker midribs; often widely flared
A. inapertus is a clump-forming herbaceous perennial 90-150cm or more highwith deciduous, rather upright, strap-shaped leaves, up to 70cm long and 2-3cm across, and stiff, upright stems topped by umbels, 10-15cm across, of hanging flowers, 2.5-4cm long, in late summer and early autumn; the flowers are in shades of blue, often purplish and sometimes very dark in colour, and are tubular with the segments barely open at the mouth
A. reptans is a spreading stoloniferous perennial to 15cm in height, forming a wide mat of dark green obovate leaves, with erect spikes of dark blue flowers in late spring and early summer
A. caeruleum is a bulbous perennial up to 80cm in height, with narrow leaves often withering by flowering time. Starry blue flowers are borne in compact, rounded clusters in early summer
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