Gardenias can be grown indoors, but because they tend to be fussy and have very specific requirements that must be met, they shouldn't be considered an easy-to-grow houseplant. If you have the patience and dedication to grow gardenias, the resulting dark green foliage, spectacular cream colored blossoms and sweet aroma will be well worth the effort. In some cases, a healthy gardenia will grace your house with big double blooms all year around.
Begin with a healthy gardenia from a greenhouse or nursery. The leaves should be a glossy, bright green, and the plant should have small buds that are just beginning to develop on the ends of leaves and on the stem.
Provide plenty of bright light for the gardenia, but keep in mind that the plant should be kept fairly cool. In the daytime, the gardenias do best in temperatures between 65 and 75 degrees. During the night, the gardenia should be located where temperatures won't be higher than 65 degrees, or the plant won't bloom. Don't put the gardenia where it will be exposed to drafts.
Keep the gardenia moist, but never let it get soggy or allow the roots to sit in water, and, if possible, water it with distilled water. Gardenias thrive in high humidity, so if you live in a dry climate, you may need to use a humidifier, especially in the winter.
Feed the gardenia with a high quality, water soluble fertilizer every other week during spring and summer. During the fall and winter months, the gardenia should be fertilized once a month. A fertilizer formulated especially for gardenias will be best.
Re-pot gardenias every spring for the first two to three years. After that time, they only need to be re-potted if they become root bound. Gardenias don't usually require pruning, but the flowers should be removed as soon as they've finished blooming.