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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. 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
'Ashby' is a bushy plant growing to 90cm tall and wide at maturity. The lobed, scented leaves are mid- to dark-green and flowers are a pink-purple colour with dark central markings on the upper petals
'Millennium' grows to 1.8m, with long stems bearing strongly fragrant flowers 6cm across, the standards deep reddish-purple, the wing petals vivid purplish-red
R. campylogynum is a dwarf evergreen shrub with small, glossy leaves, glaucous beneath, and open bell-shaped, pale or deep rosy-purple or pink flowers 2.5cm across in late spring
C. brachytricha forms a clump of glossy green, linear leaves turning yellow in autumn, with narrow, fluffy, purple-tinged plume-like sprays of flower opening in late summer and early autumn and persisting into the winter
'Hello Darkness' is a vigorous, spreading plant with glaucous foliage to 65cm, erect, or lax at edge of clump. Standards are overlapping, purple with blue and violet tones, paling towards centre. Falls are drooping to incurved, velvety with crimped margins, deep purple violet approaching black. Beard fairly conspicuous, violet blue. Mid season
H. sieboldii is a small, compact, clump-forming perennial. Leaves are narrow, lanceolate, to 15cm in length with mid-green centres and narrowly-edged with white. Funnel-shaped, lavender-coloured flowers, on stems to 60cm, appear in mid to late summer
'Genii' is an erect medium-sized deciduous shrub with yellow-green foliage. Flowers single, small, with narrow, up-curved cerise sepals, slender cerise tube and reddish-purple petals
T. tricolor is a summer-dormant, tuberous, perennial climber to about 1.5m with small, light green, five- or seven-lobed leaves. The small, yellow flowers are surrounded by a showy purple-tipped, orange-red calyx with a long red or purple spur, in all about 3cm long. Flowering takes place from winter to early summer
'Rodomont' is a trailing plant with stems to 30cm, and semi-double, deep rose-pink flowers, the lower petals streaked with purple
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