Gardenia or cape jasmine (Gardenia jasminoides) is hardy in U.S. Department of Agriculture plant hardiness zones 8 through 10, while white gardenia (Gardenia thunbergia) is hardy in USDA zones 10 through 12. These plants are generally beloved for creamy white, fragrant blossoms, but they are notoriously difficult to care for. However, you can at least avoid the mistake of pruning your gardenias at the wrong time and losing your floral display.
Respecting Bud Development
Because gardenia flowers form on old growth, if you hack up your shrub before the flowering period, you will likely lose most, if not all, of your blooms. To avoid this, wait until after gardenias have finished flowering, and then prune them to the desired shape. If you are waiting for plants to bloom and instead they drop their flower buds, this could indicate soil that is too dry or wet, overfertilizing or other chemical contamination, and soil nematodes.
Using Best Techniques
For the most part, even after they have flowered, gardenias do not typically need much pruning, so avoid pruning them back hard unless there is a problem. When you do prune, do so right after flowering. For cultivars that produce a light rebloom later in summer, immediate pruning after flowering will also reduce the chance of removing these buds. Pruning too late in the summer or early in the fall can also reduce winter protection in areas that sometimes experience frost, so avoid it if you live at the lower end of gardenia’s hardiness zone range.
Removing Damaged Branches
You can and should remove damaged or diseased branches at any time of year, regardless of whether or not the spring flowering has occurred. Because wounded branches provide entrance wounds for diseases, leaving jagged areas open is a bad idea. Instead, neatly clip the branch off at the first junction below the site of damage to give the tree the best chance of healing quickly. To avoid transmitting disease, dip pruning tools in a solution of 1 part 70 percent isopropyl rubbing alcohol and 1 part water between plants, or between cuts when pruning diseased plants.
Determining Location Fitness
Normally gardenias grow to a pleasing shape. If they're located with a sufficient planting area they won't outgrow, they don’t need much pruning. If you find you are pruning your gardenias every year, you likely haven’t chosen a very good planting area. Although the shrubs will tolerate the trimming, if you relocate them to a spot where they have room to reach their full height and span -- about 4 to 8 feet in every direction -- you can save yourself a good deal of work.
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