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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
While we update our systems with the new hardiness ratings you may still see old
hardiness ratings in your search results. These are denoted as 'Old'.
For full details of the hardiness ratings see
AGM plants have been through a rigourous trial and assessment programme. They are:
E. agavifolium is a handsome evergreen perennial forming a rosette of sharply toothed, sword-shaped leaves to 45cm long, with small, green thimble-like flower-heads on branched stems in late summer
E. bourgatii is an herbaceous perennial to 45cm tall, with deeply lobed and silver-veined leaves, and vivid blue, branched stems bearing cone-like flower-heads with narrow, spiny, usually silvery-blue or violet bracts
E. alpinum is an erect herbaceous perennial to 90cm, with heart-shaped, glossy dark green basal leaves. Large, cone-like, purplish flower-heads surrounded by 6cm in length vivid blue, spiny bracts, borne on blue 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
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
'Silver Ghost' is an erect, branching biennial with cone-like heads of blue flowers surrounded by spiny, silvery-white 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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