Gardenia is a lovely bush that produces sweet-smelling white flowers. However, there is a chance that the location of your gardenia just doesn't suit it well. Maybe there is not enough room where it is, leaving it in competition with another plant, or it's no longer getting the right sun. Either way, the best thing to do is transplant it to a better location. Gardenias are tricky plants that don't always take well to transplantation. Below are some steps to improve your odds.
Step 1: Health
Do not transplant a gardenia in poor health. If it's suffering from mildew or disease or otherwise damaged it will not survive transplantation. Either solve these problems before transplanting or get a new gardenia, because this one won't make the move as it is.
Step 2: When to Transplant
Gardenias are best transplanted in the fall. Wait until the blooms are gone and the weather is cooling. Your bush will slow down, and the move won't shock it as badly.
Step 3: Where to Transplant
Once you have decided to transplant, it's vital to find a better location for your gardenia. Th bush needs rich soil and light shade to flourish at most latitudes. The latter should be present wherever you plan to transplant. The former can be created if it is not already present.
Step 4: Preparation for Transplantation
About a week before transplanting your gardenia, trim the bush down by 1/4 to 1/3 of its original size. This will turn the bush's focus from its leaves to its roots, and leave it in a better state to reestablish itself after transplanting.
Enrich the soil of the location where you are going to place your gardenia. Add organics and nutrients. Purchase a soil pH testing kit from your garden supply store and check the pH of your new location. Gardenias prefer a soil pH between 5.0 and 6.0. If that is not present, add an acidic compound to decrease the pH. Sphagnum peat is a bit expensive, but will add rich organics as well as acidity to your soil. Granular sulfur is the most common way of lowering soil pH.
Step 5: Prepare the Hole
Have the hole ready in the new location before you dig up your gardenia. The faster you put the roots back in the ground, the better for the bush. Make sure the hole is large enough. You want to take as much of the root structure of your bush as possible, and the roots can extend as wide as the bush itself.
Step 6: Dig Up Your Gardenia
Dig as big a root ball as you can. The more root structure you can maintain, the better your gardenia's chance of surviving the move. Work your shovel into the soil until you can lift the bush.
Step 7: Place the Gardenia
Place the root ball into the hole you prepared earlier. Tamp the soil down with your foot to ensure contact between the roots and the new soil. Fill the gaps with fresh soil from the new location. Water well to minimize air pockets and encourage new growth.
Step 8: Follow Up Care
Continue to water well every other day for at least a week. Watch your gardenia well and provide nutrients and water as it reestablishes itself in its new home. By next spring you should have a beautifully blooming bush full of sweet smelling flowers.