Growing Gardenias Indoors
Gardenias were discovered in China in the 1700s. Their fragrance is unmatched in the floral world, and the oil extracted from the flowers is used for make both perfumes and teas. Some folks think gardenias are fussy plants. We say they're not: they're simple to grow if you meet a few of their basic needs.
Gardenias need at least four hours of sunlight daily (most blooming plants have basically this requirement, although there are exceptions). Without at least this much light, they just won't bloom. However, in our fairly brutal summer heat, some afternoon shade will protect the gardenia‘s foliage from burning.
Gardenias don't like to dry out, so keep their soil moist but not soggy. (Never let them stand in water!) During the winter, the plant may use less water due to decreased evaporation from heat and sunlight, so you can cut back some on watering, letting the top half inch of soil dry out before you give your plant a drink.
Gardenias do enjoy humidity. Unfortunately, most homes simply contain dry air, especially in winter when central heating contributes to the problem. You could buy a fancy pebble tray, but you can make your own, more economical version that will work just as well. Simply get a large plastic plant saucer. Fill it about 3/4" deep with gravel. Add water almost to the tops of the pebbles. (You don't want your plant sitting in water at any time.) The evaporation from this saucer will keep at least the immediate area around your plant comfortably moist.
Pay attention here! If the temperatures aren't right, your gardenias will drop their buds in protest.
Daytime temperatures that suit humans are just fine for gardenias. At night, though, they much prefer a temperature ranging from 50-55°F. You might be able to sneak by a temp as high as 63°, but you'll be pushing your luck.
Gardenias are acid-loving plants, so use an acid-based fertilizer. These are clearly labeled as being for acid-loving plants. You can certainly cut back on fertilizer in the winter, but generally a monthly regimen is fine for your plant.
Gardenias don't often outgrow their pots. Don't bother with repotting unless the roots have almost filled the pot. Always use a well-draining, peat-based soil to which no lime has been added. (Again, for the acidity the plants love.)
If you're following these guidelines carefully, bud drop should not be a problem. If it occurs, check growing conditions again. The problem should correct itself if you fix the cause.