Given the vast variety of gardenias, it can be hard to know exactly the right time to prune this shrub. In fact, you might be tempted to do nothing at all. However, experts recommend pruning yearly to maintain shape, size, and health. Follow these suggestions for knowing when to prune and you will enjoy sweet smelling gardenias for years to come.
Generally, the best time to prune a gardenia is when it starts to fade after blooming in the summer. Cutting back your plant at the end of its flowering cycle will not damage the gardenia since for many varieties, new buds do not start forming until the fall. There is no chance of cutting off the new growth. However, you should be careful not to prune until you are sure the flowering cycle is over.
To determine if your gardenia's flowering cycle is complete, you need to know what variety you own. Gardenias can have longer or shorter cycles. Some gardenias like the mystery variety bloom only once in the summer from the previous years growth. Others bloom, wither, and then blossom again on new buds. For example, varieties like august beauty flower during May on buds from the previous fall and continuing flowering on new buds that form that summer. In addition, kleim's hardy also blooms from old and new wood formed during that season. If you prune a gardenia that flowers over several months in this way, you risk losing that current season's growth. Take pictures of your particular plant and consult a local nursery for specifics about your variety.
After blooming, wait until the white blossoms have fallen off the shrub. Decide on a shape and cut back both green and brown wood. Use sharp shears to prevent uneven cuts and the spread of disease. Leave 4 to 6 inches on every stem.