Gardenia shrubs can be shaped by pruning into various forms, including a tree silhouette. As tropical flowering perennials, gardenias should be pruned only in the the summer or early fall after flowering for the year has completed. Regular maintenance pruning to remove dying leaves and faded blooms should be done once a month around watering time to keep them looking tidy. Significant hard pruning should be done every year or less frequently if needed at all.
Harvest fresh blooms for use in short stem or floating flower arrangements. Deadhead the faded blooms that remain on the plant when they begin to brown and wilt. Cut away the blooms with secateurs or simply pinch them off using your thumb and index finger.
Inspect your gardenia once a month or so at watering time as part of a maintenance pruning regimen. Look for for any damaged or diseased leaves or branching and cut away any that you find. Pull out any spent flowers that have fallen and gotten stuck in the canopy. To maintain a tree form, cut away any branching or leaves that sprout from the trunk below the desired tree-shaped canopy.
Hard-prune your gardenia tree once a year or so to control the shape, re-size or correct the shape and restore the tree's natural symmetry after damage. Cut back the stems to the desired length, making sure to place all of your cuts at least 1/4-inch or so above a leaf node. Remove only up to 1/3 of the foliage in any one pruning session to reduce stress on the gardenia and prevent shock.