Since younger gardenia branches produce more blossoms than mature or woody branches, removing old branches stimulates new growth, thus encouraging a larger crop of flowers. Gardeners also trim or prune the plant to shape the bush or thin out undesired growth. Unfortunately, if the gardener trims the shrub when new buds are forming, he can inadvertently remove new bud growth.
Blooming time can vary for the gardenia, depending on the climate and temperature of the area. While it typically stops flowering during the summer, it is possible for the gardenia to continue flowering into September, depending on the region. It is important to note the flowering time of your gardenia because trimming should take place immediately after the plant stops blooming and before it begins to set its new buds. In areas where the plant stops blooming in early summer, the plant might begin setting new buds in mid-summer.
Trim the gardenia using sharp blades to make clean cuts. When cutting off a branch, remove the entire branch, and cut closely to its connecting branch, without leaving a stub and without tearing the bark. If the gardenia plant is old and poorly shaped, severely trim the plant, cutting the gardenia virtually to the ground, leaving just 6 to 8 inches. Do this after the danger of frost has passed.
When you trim your gardenia, always sanitize the blades of your gardening shears to avoid exposing the plant to disease-causing bacteria or fungi. One way to sanitize the blades is by wiping them with a cloth saturated in rubbing alcohol. Gardenias are challenging because they dislike extreme cold and temperature fluctuations. Garden centers typically market the plant around Mother's Day, in time for its first blossoms of the season. Some consumers raise gardenias as houseplants. When grown indoors, the plant needs exposure to plenty of sunshine and humidity and prefers a daytime temperature of 68 to 74 degrees F, with no lower than 60 degrees F in the evening.