Gardenias are perennial shrubs that have flower blooms that are popular in floral arrangements. However, gardenias are very difficult to get to bloom, since they are very picky about the temperature, moisture of the soil and most importantly the humidity. Even more frustrating, the gardenias can develop fungal leaf spots if misting is used to simulate humidity.
Gardenias came from China and have been cultivated for 1,000 years. The British discovered these plants and brought them to the British colonies. Today, gardenias are mostly found in Florida, which has sufficient humidity for them.
Fertilizers should be added to gardenias every three weeks. These fertilizers should be acidifying. When pruning, leave some leaves on the gardenias so that they will keep their root systems alive. When spring arrives, add chelated iron and a greater amount of nitrogen in order to help the gardenia grow leaves and buds. Gardenias should be pruned when dormant because they'll be able to heal the damage done by the pruning during this dormancy period. Pruning during the flowering period will sap the gardenia of its energy and lead to fewer flowers. Pinching the tips of the gardenia can help the gardenia develop a greater bloom the next year.
Gardenias mostly need as much sun as possible. But in really hot areas, some shade is sometimes needed. Temperatures of 70 degrees F or higher and 62 degrees F or higher at night will prevent gardenias from blooming.
The soil of the gardenia should have peat moss and should be composted. Mulch is very important for gardenias because tilling can damage their roots, so mulching is needed to protect gardenias from heat, water moisture and weeds. The soil acidity of gardenias must be between 5 and 6 pH. The soil must be kept moist as much as possible, though sogginess can make the gardenia susceptible to root rot.
The environment should ideally be humid, which aids the plant in transpiration and also keeps the soil moist. However, misting the gardenia in order to artificially create humidity is not recommended because the gardenia will likely develop a fungal leaf problem. The temperatures at night must be cool, which is what gardenias have adapted to.
Gardenias often experience bud drop, which leads to the flower buds falling off the gardenia without blooming. This bud drop is often caused by a lack of humidity, over-watering, under-watering, temperature fluctuations and sudden cold drafts. Gardenias can develop cankers, which show up as a swollen appearance on the stem. This disease can kill the gardenia and can spread to other plants, so diseased gardenias should be removed. Bacterial leaf spots can cause deflowering and can be cured by sterilizing the soil. Rhizoctonia leaf spots can be caused by overwatering, and infected plants should be destroyed.