Baffled by my Brugmansia

Right from the beginning of this season, my beautiful and nearly four metre high,  five-year old Brugmansia – also known as Angel’s Trumpet – has had not so beautiful yellow leaves and I’ve been puzzling over the cause.  I’m feeding it with organic high-potash tomato feed, so I don’t think it is too much nitrogen, I’ve given it a couple of  doses of Epsom Salts in case it was a magnesium deficiency, to no avail and I’ve also top dressed it with Grochar Fertiliser, which usually fixes everything.

I’m now beginning to suspect that despite it being in a very large pot, the pot is entirely filled with rootball and the plant is struggling to absorb sufficient nutrients. So, I’ve decided that this autumn, when I cut it back by half to overwinter, I’m going to take cuttings and start again, but in the meantime its beautiful fragrant trumpet flowers, intertwined with mina lobata mean that it is still beautiful despite its yellow leaves.