Gardenia is one of the most popular southern garden plants, but they are not suited for every garden. Before you purchase your gardenia bushes, contact your local county extension office to arrange a soil test. Like most other plants, gardenia needs nutritious soil. But more importantly, it needs slightly acidic soil: between 5.0 and 6.5. If your soil's pH level is slightly more alkaline than that, it can be amended with an application of gardening sulfur.
Dig a hole that is as twice the diameter of the gardenia's current container and just as deep.
Remove the gardenia bush from its container. Be careful not to damage the plant's roots.
Place the gardenia bush in the hole so that the top of its root ball is slightly above--but no more than 1 inch above--ground level. Fill half of the hole with soil. Then fill it with water so that the soil settles. Then finish filling the hole with soil. Do not cover the gardenia bush's root ball with more than 1 inch of soil.
Build a 3-inch-high watering berm or dam around the planting hole.
Fill the berm with water from a slow-running hose. Check the gardenia bush's soil frequently. Fill the berm whenever the top inch or so of the soil feels dry (at least twice weekly) until the gardenia bush is firmly established and producing new growth.