Happy to report that giant Echiums are starting to colonise my street in south London. These are E. wildpretii in my neighbour's front garden. They are the progeny of one I grew in my front garden a number of years ago. 

 Hailing from the Canary Islands they are triennial i.e. a seedling/rosette appears in the first year, then puts on about a metre of growth in the second year, then raises the towering spike of flowers in the third year. After flowering the whole plant dies having dropped copious amounts of seed.

 The blue flowered E. pininana is well established in the back gardens and wildpretii will hopefully do the same at the front.