Solved Can anyone ID this exotic-looking plant?

I’ve 6 or 7 Snow Towers in the greenhouse and undercover outside for their second winter, and they seem to have survived ok up here, and one of the few things needing watering/feeding over the winter. It seemed like a good idea/challenge to grow this supposed 15ft triffid from seed(surprisingly successful though), and crunch time is fast approaching as to what to do with them.

Seems from your experiences that they might do ok keeping them in the pots, as the other option I realistically have is to dig up round holes in the lawn and let them loose to do their thing. If they get anywhere near their supposed height this year, there’s no way they’ll overwinter again in the greenhouse. I want to give them a chance to reach flower, but appreciate it’s a case of ambition over reality given the less than favourable summers we have in NE Scotland compared to you guys down south. They really are otherworldly though and well worth the effort of bringing on, so far anyway. Will leave crunch time till later, they’re just fine just now giving me a friendly prickle navigating past them.

 

My Echium pininana have been outside since I moved the seedlings last summer, they are now all over 8ft tall. Down here they can even be a bit of a problem self seeding happily.
The RHS give the leaf length as up to 7cm, I think they are out by a factor of 10.

 

I've got a couple of self sown E pininana which have made it up till now this winter, last year I had some second year ones killed by the combination of rain and frost.

Minus 5 seems to be the turning point regarding survival or not.

I've grown them in pots often, they don't get anything like as tall but are still worth growing, of course they die after flowering.
I've got a few E wildpretii coming along in pots, its not quite as hardy pininana so they will stay potted.

 

Echiums, I find, are one of those plants that really do show you if they are happy.
A few years ago I collected some seeds of our wild Echium vulgare, they were growing in shingle at Dungeness and about 12 to 18 tall.
In my garden they were rampant and soon got out of hand over 3ft tall.