Gardening Reference » Gardening in 2002
Gardenias are one of the more difficult plants to grow and bloom indoors successfully. Gardenias are not easy to bloom indoors because they have rather strict temperature requirements. Temperatures between 55 and 65 degrees are essential when gardenias are in bud or bloom. Bud drop occurs above 70 degrees. Bud deformity occurs below 55 degrees.
Letting the soil get too dry will also cause bud drop. In addition, a change in environment will also sometimes cause bud drop. Do not repot or fertilize when it is in bud. Direct sunlight, high humidity, and acidic soil (5.0 pH) are also important for maintaining gardenias successfully. Avoid repotting until it is utterly potbound. Use an acid fertilizer, such as Miracid, but don't overdo it.
Gardenias can bloom at almost any time of the year. Flower buds form according to the following regimen: Prune back old growth (usually in spring); promote new growth with lots of light and warm temps during the day (summer); allow temps to drop to 60 degrees at night (fall or early winter). It is up to you to decide when you want to introduce this regimen. Obviously, it is harder to achieve the lower nighttime temps during the summer.
It is difficult for most people to provide these conditions. Some are satisfied to keep a gardenia as a foliage plant.