Echium pininnana

Tall spire of many small blue or bluish flowers that are attractive to bees

Monocarpic plant that lives for 2-4 years. Dies after flowering but reliably self seeds especially in gravel. Height if well grown 2-3 m sometimes more. In poor soil expect 90-150 cm. Produces a rossete of leaves. Protect the central crown of the plant from frosts although if as severe as -5c it is likely to perish. 

Currently sold in 7cm square pots for a limited time.