Martin Brown writes

K wrote:
I have two brugmansia which I grew from seed. One is heavily scented, a
butter-yellow variety of one which is, I think, normally white, and has
flowered happily for the last four years.

The other is a different species, about 3 years old and 5 ft high, and
has never flowered. I feed it regularly with tomato fertiliser. I had a
feeling that maybe it needed a certain amount of heat to persuade it to
flower, so this year I've left it in the greenhouse, but still nothing
(the other has been flowering since June on a S facing terrace).

So - any ideas to encourage flowers?

Some need a bit more warmth than others to get going. High potash feed
and less nitrogen also encourages them to flower as does a bit of
benign neglect of watering. Plants that feel a bit threatened by
environmental stress often flower soon after as a result.

I've given it all the heat that is available, and the tomato feed is of
course high potash. They get the benign neglect by default.

If you know the species then one of the experts may be able to tell you
what to do to initiate flowering in the UK. My outdoors ones are back
up to flowering size now in N Yorks.

"Back up" to flowering size? - what happened in between?

"Outdoor" - presumably outdoor summer only? In pots, or in the ground?
--
Kay