There are many cultivars of this species all having variations of blue flowers and some are slightly smaller in growth habit.
Cultivars
'Blue Angel'
This perennial produces masses of vibrant blue flowers.

'Feltham Pride'
This smaller perennial is often grown as a biennial and produces clear blue flowers.

'Little John'
This dwarf form grows to 450mm (18in) tall and produces deep blue flowers. It is commonly grown as a front border plant in small gardens and is long lived.

'Loddon Royalist'
This upright perennial has strong stems to 900mm (36in) tall and produces bright deep blue flowers.

'Morning Glory'
This perennial grows to 1m (3ft) tall and produces deep blue flowers.

'Opal'
This perennial grows to 1m (3ft) tall and produces pale blue flowers.