I always thought the gardenia to be an outdoor plant. Mine is in the ground. I live in the West Indies and it flowers year round. ... View related article.
It does look like the Dieffenbachia and it can be quite beautiful when it grows well. I'd take some out of the pot and plant in a light soil. If it can be placed in an area where there is a bit of the morning sunlight then I'd also try that; but definitely not harsh sunlight. Dieffenbachia leaves are also know to be poisonous if ingested so you have to take care with children and pets. ... View related article.