Gardenia shrubs, with their fragrant, waxy blossoms, are the queens of the flower garden. Gardenias are also one of the harder shrubs to care for, particularly if your local climate is warm. If you are located above zone eight, you are able to keep them indoors.
These attractive shrubs have glossy, evergreen leaves and grow to a height of 2 to 6 feet tall, fully sun exposed and depending on the variety. Sun exposure is more flexible for them—coastal foggy areas can provide a fair amount of sunshine, but inland hotter areas need to offer afternoon shade.
Avoid areas next to the house or on the southern and western sides, as roots from the trees might interfere with the gardenia shrub’s growth. These regions tend to keep warm, which can cause them to shed their buds unexpectedly before flowering.
Add generous amounts of compost, peat moss, or manure to the soil. Gardenias like a well-drained, rich, acidic soil. If you are able to grow azaleas, gardenias should also be possible for you, provided you live in a region with mild winters.
Gardenias should be planted in spring or fall, and during the first growing season, water them frequently as the roots establish. After establishment, watering should only be performed as required to keep the soil slightly moist. Gardenias do not respond well to dry conditions.
As gardenias have shallow roots, they do not respond well to cultivation. Cover them with wood chip mulch which will suppress weed growth, slightly acidify the soil, and help retain moisture.
In early spring as new growth starts, and again in mid-summer, gardenias should be fertilized. Late fertilization, after July, should be avoided since it promotes tender growth that is easily damaged by cold temperatures.
Post blooming period is the best time to prune gardenias. Removing spent flowers along with any dead or unsightly straggly branches is recommended.
Common Problems
Iron Chlorosis happens when shrubs are unable to access iron within the soil. The symptoms manifest as yellow leaves with green veins. This sometimes happens because the soil is not acidic enough. Sulfur soil amendments can be helpful.
Also, gardenias cannot access iron when the soil is cold in winter. Here, the problem resolves as temperatures increase. In both situations, iron-containing fertilizers improve the condition.
Dropping buds/failure to bloom. These gardenias maintain strict temperature requirements. Blooming occurs only with hot days and cool nights.
If evening temperatures exceed 62 degrees or during periods of severe temperature variability, buds may be shed. Gardenias should be placed in shady locations with free air circulation, away from heat trapping surfaces.
Insect pests. Whiteflies, aphids and thrips tend to infest gardenias, especially during dry periods. With these pests comes a sticky substance on the leaves and floor, as well as webbing and wilting leaves.
Misting gardenias in the mornings helps with humidity. If symptoms have progressed to severe, it is best to apply an insecticidal oil or soap spray on cloudy cool days to the foliage.
Root Rot. The ailment root rot is characterized by decayed roots and blackened stems and is commonly associated with some fungi. This problem often occurs in overly dense and wet soils.
To mitigate root rot, add compost or peat moss to heavy soils to improve aeration and drainage. Create a slight mound around gardenias so they sit higher than the surrounding soil. Remove infected plants and any associated debris and mulch to mitigate future infections.
Growing Gardenias Indoors
Gardeners from northern regions can grow gardenias as houseplants, but they tend to be hardier and require more maintenance than one might expect. Like many other plants, gardenias require direct bright sunlight, cool temperatures, and stable humidity levels. Meeting these environmental conditions can increase the likelihood of success.
Ensure the gardenias are placed in a brightly lit room with southern exposure, as well as placed near windows that receive plenty of sunlight.
Water the soil thoroughly to maintain slightly moist levels, avoiding sogginess. Turn on a room humidifier to add moisture to the air, particularly in winter when warm dry air is prevalent due to heating systems.
Plant food with acidic properties should be used roughly every four weeks and during active growth periods to support vigorous growth and increase bloom size. Correct use of fertilizers will yield greater results than incorrect dosing.
While indoor gardenia remain smaller than outdoor specimens, they benefit from regular pruning to control shape and remove tired wood and faded flowers.