it's one of the Solidago species. I have a variety called Goldkind which only gets to 18"

I have Solidago Golden Wings which is much taller, certainy 4'+. It could be that one. I transplanted a bit of my original plant to another part of the garden. This year it only reached 4' but the original has flowering stems up to 8'. It seems to favour the less acidic soil.

Its common name is Golden Rod.
At the other end of the scale we grow 'Solidago virgaurea minuta', which is a tiny cushion forming plant, on the rockery.

'Solidago virgaurea minuta'
Don't know that one. I have S. cutleri (syn brachystachys) and that gets to about 9 inches.

Only 2 to 3 inches for this, Owdboggy. I got mine from the SRGC seedex 2010/11 and I note that the AGS listed it in the same year - probably the same donor.

I must look and see if it is offered again then.

What's a pity is that ordinary old golden rod seems to have disappeared from suppliers lists. Best obtained now from alongside railway lines!

Disappeared as it is such a pest. I have dug out hundreds of seedlings over the last few years.
Now I will tell you what has disappeared from the lists, is the cross between Solidago and Aster. Solidaster, a really nice plant too.

Owdboggy the beth Chatto Garden has one http://www.bethchatto.co.uk/s-z/solidaster/x-solidaster-luteus-lemore.htm

Ta, a bit far to go for us.

Have you looked in the RHS Plant finder. You might find a GC or nursery closer to you who would have it. I do not buy mail order as the postage is often more than the plant costs.