Cultivars
'Arthur Simmonds'
This plant has dull dark leaves and produces bright purplish blue flowers.

'Dark Knight'
This plant has silvery grey leaves and produces dark blue flowers.

'Ferndown'
This plant produces dark violet blue flowers.

'Heavenly Blue'
This erect plant produces very dark blue flowers.

'Kew Blue'
This plant has grey green leaves that are silvery beneath and produces dark blue flowers.

'Worcester Gold'
This plant has yellowish leaves and produces lavender blue flowers.