How to Grow Gardenias
Gardenia shrubs are prized by gardeners for their highly fragrant flowers and bright, glossy, evergreen foliage that’s attractive year-round. When given the right growing conditions, these heat-loving shrubs will thrive. Choose the right place to plant a gardenia and give it the specific care that it needs, and you’ll be rewarded with romance and beauty. Selecting the right variety While all gardenias sport fragrant flowers, there are marked differences from variety to variety in mature size and bloom time. First decide what role your gardenia will play in the landscape. Will it be a centerpiece of a border or line a foundation with plenty of room to stretch out? Do you need a tidy, low, flowering border along a walkway or edging a bed? Are you trying to fill a large pot that will sit on a deck or patio? There is a gardenia variety to suit just about every landscape design need from compact smaller varieties that mature to 4 feet tall (such as Everblooming Gardenia) and others that top out at 8 feet tall and wide (such as First Love® Gardenia). Also, take into account blooms and bloom time. Some gardenias offer fewer but super-large 4-in diameter blossoms or while others have smaller, but more abundant flowers. By planting several gardenias with different bloom times it's possible to have a sequence of flowers from May through August. Optimal conditions
- Zone: Gardenias are subtropical plants that thrive in warm, humid weather. Most gardenias are hardy in zones 8-11, though a few varieties hardy to zone 7 have been developed (Kleim's Hardy gardenia is one), and a few are only hardy in zones 10 and 11 (including Double Tahitian gardenia).
- Soil: Gardenias require a soil pH of between 5.0 and 6.5, which is considered acidic to slightly acidic. It's wise to take a soil test with a simple kit available at nurseries and home-improvement centers. If the soil pH is too high, amend with sulfur, which is available in a variety of chemical forms. If possible, amend the pH up to six months or a year before planting to allow the application to work. In addition to the right pH, the best soil for gardenias will be a lightweight and full of organic matter with good moisture-retention properties. If your soil is heavy and clay, or very sandy, amend with copious amounts of compost. If planting gardenias along a house's foundation, test the pH; soil around the foundation can have a much different pH than soil in the center of the garden.
- Moisture: Constant moisture is non-negotiable for gardenias. They’re not drought-tolerant, but they also don’t want soggy roots. It’s essential that you site them in an area with well-drained soil. Organic matter helps retain moisture at the level the shrubs need. Too much clay can lead to waterlogged soil while overly sandy soils dry out quickly and don’t retain nutrients.
- Light: Gardenias can handle full sun, but need protection from baking midday or afternoon sun in higher growing zones. North and east-facing exposures are ideal because they will receive bright morning light and some midday light, but won’t be in full sun all day or during the absolute heat of the day.
- Sooty mold: Sooty mold is a gray, fuzzy mold that covers the plant leaves and is a symptom of a whitefly or aphid infestation. Rid plants of those pests using insecticidal soap and mold will recede.
- Bud drop: Lack of adequate water during the summer can cause bud to drop so it’s important to always irrigate during dry weather. Lack of sunlight can also lead to bud drop or even cause the plants not to form flowers. Finally, insect problems from aphids or whiteflies can cause bud drop. Eliminate issues one by one, and you’ll have a gardenia covered in blooms.
- Yellowing leaves: Root rot can lead to yellowing leaves. Try to pull the plant up. If it come s out of the ground easily and the roots are mushy, root rot is the culprit and the plant should be discarded. Iron chlorosis (iron deficiency) causes yellow leaves; adjust the soil pH and, possibly, apply a foliar feed of iron.
- Failure to set flower buds: Usually when a gardenia flat out won’t produce flower buds it is growing in too much shade. Move it where it will get more sunlight. Sometimes an aggressive late summer pruning will interfere with flowering as well.