can Gardenias do well in a planter? If so haw large should they be?
I live in a condo my yard space is very limited
Yes, Gardenia can grow in containers.
The container you choose is determined by how large of a plant that you start with. When you purchase from a garden center; the plant is likely in the correct size pot for it's age.
Repotting the Gardenia is done when the roots begin growing from the bottom of the flowerpot, it's time to repot the gardenia. Wait until late spring, after the shrub finishes blooming, to avoid damaging the flower buds and blossoms. The new flowerpot should be 1 to 2 inches larger in diameter than the previous pot.