Hi Mike, The age old question of bougy ferts...
As Art says its all to do with water mainly...the less the better...and you have to get full sun...as much as possible...sun is very important...
I'm currently feeding mine a low nitrogen fert 6-8-10....Too much nitrogen goes into making bigger greener leaves...And I'm drying them out as much as I can in the next week to go into our local show...but alas its pouring rain...
This is my hollow bougy in flower...the back of it anyway....and a shot up her trunk looking at the sky...she's completely hollow...
The last small pic is of a bougy about 3 hours drive into the desert here...It recieves no water or fertilizer(apart from gasoline and diesel) It's located next to a petrol bowser as you can see...and aint she just magnificent!
I'm just keeping the leaves in a semi wilted state as much as possible and it seems to be working well...
Good luck
Tai
