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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:
E. yuccifolium is an evergreen perennial with sword-shaped, spiny-edged, blue-grey leaves and branched stems bearing small, egg-shaped white flower-heads in late summer
E. × tripartitum is an herbaceous perennial with a basal rosette of grey-green leaves, and erect, much-branched, violet-blue stems bearing cone-like purple heads surrounded by narrow, dark blue bracts
'Taplow Blue' is a robust, upright herbaceous perennial, with divided, prickly dark green leaves whitish beneath. Rounded, steel-blue flower heads on branched, leafy stems
E. giganteum is a robust biennial or short-lived perennial forming a rosette of heart-shaped basal leaves, and spiny stem leaves, with cone-like umbels of tiny blue flowers sitting within a rosette of spiny silvery-grey bracts
E. variifolium is an evergreen perennial to 40cm tall, forming a clump of rounded basal leaves with white veins, with branched, leafy stems bearing silvery-blue flower-heads with narrow, spiny silver bracts
Graham Thomas's selection of E. bourgatii is a compact perennial with handsome foliage, the grey-green leaves having prominent white midribs, and violet-blue flower-heads to 10cm wide open in mid summer
'Big Blue' is an upright, herbaceous perennial to 75cm with spiky, highly-divided, silvery-green foliage. The stiff, branched stems are topped with blue, thimble-shaped flowerheads surrounded by a ruff of prickly, silvery-blue bracts
'Neptune's Gold' is an upright, herbaceous perennial to about 50cm. The foliage and flower bracts are spiny and yellow green, while the flowers are electric blue. Rounded heads of tiny flowers appear in mid- to late summer, and the seedheads often remain decorative into winter
E. × oliverianum is an erect herbaceous perennial to 90cm, with strongly toothed, heart-shaped leaves and branching violet-blue stems bearing cone-like flowerheads surrounded by narrow, spiny, metallic-blue bracts
'Oxford Blue' is an erect herbaceous perennial to 40cm, with clumps of deeply divided basal leaves with prominent whitish veins. Cone-like, deep blue flower-heads 2cm in length are surrounded by silvery-blue, spiny bracts
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