The key to coaxing a gardenia bush to bloom all year is consistency. Only gardenias that are grown in an environment that is consistently warm and humid can be tricked into thinking that it is spring all year round. Gardenias are notoriously finicky plants, and it may take you a season or so to perfect your gardenia care. But the rewards are worth it. Few flowers rival the gardenia's beauty.
Keep your gardenia bush humid. If it is growing in a pot, fill a planting tray with pebbles and water. Place the tray underneath the gardenia pot and as the water evaporates, it will increase the humidity in the air surrounding the gardenia. If your gardenia is growing in the ground or you don't have a planting tray, mist the gardenia with water daily.
Provide your gardenia with just the right amount of sunlight. Gardenias need full sun with shade provided during the hottest part of the day. Indoor gardenias should be near a window with southern exposure where they can receive indirect sunlight.
Keep your gardenia warm. Gardenias grown indoors are ideally suited for year-round blooming as long as the temperature is kept between 65 and 75 degrees F during the day and 55 and 65 degrees F during the evening.
Fertilize your gardenia regularly. Give your gardenia a commercial, water-soluble 15-5-15 flowering shrub fertilizer once every two weeks. Once every three months, substitute the general fertilizer with a special acid-based liquid gardenia fertilizer. Follow the package instructions for application rates and amounts based on your gardenia's size. Always water your plant after fertilizing it.
Keep your gardenia's soil moist by checking its moisture level frequently. Water your gardenia whenever the top few inches of the soil or the top one-third of the container's soil dry out. Water gardenias planted in the landscape with 2 inches of water or until the soil is moist and water potted gardenias until soil runs out of the drainage holes in the bottom of the pot. Do not allow your gardenia to become drought stressed or it may drop its buds.
Spread 2 to 3 inches of organic mulch around your gardenia's planting area (but keep it at least 3 inches away from its base) to help the soil retain moisture.