| Den nobile isn't native to Africa. They're from South East Asia. Now I'm really puzzled. I dont' know the whole genus well enough to know if there are any dens native to Africa.
If it indeed the species, I wouldn't fertilize it at all, not even when its growing. When the new canes mature, gradually decrease watering until it's gettign no water at all. Don't water and give it high light during the winter months. Keep it cool, as low as 40F winter nights.
__________________  |