Information on Growing Gardenias

Plant gardenias in window boxes if you like their fragrant blossoms.

Gardenias are a tricky plant, even for the more experienced gardener. Native to China and Japan, gardenias can be grown as a house plant or an outdoor evergreen shrub.

Appearance

Gardenias, also commonly referred to as cape jasmine, are perhaps known best for their fragrant blooms. Rose-shaped, these white flowers have a waxy appearance and are considered a gardening symbol by many in the Southeast.

Growing Conditions

Climates with temperatures ranging from 68 to 74 degree Fahrenheit are ideal for gardenias. In the United States, gardenias do best in the south or on the West Coast. Indoor gardenia houseplants need at at least half-day's worth of direct sun, moderate humidity, steady supplemental watering and nutrients to do well. If growing as an outdoor shrub, which can reach anywhere from 2 feet to 8 feet high (depending on the variety), full sun to partial shade is advised.

Planting Outdoor Shrubs

Test the soil's pH level before planting and add sulfur to reduce the pH if necessary. Gardenias prefer a soil pH of 5.0 to 6.0. Space plants 3 to 6 feet apart, and dig holes three times as big as the root ball. After placing the root ball in the hole, fill halfway with soil and water well eliminate any air pockets. Fill the rest of the hole with the remaining soil after the water drains and water again thoroughly.

Care & Maintenance

Gardenias need at least 1 inch of rain or supplemental watering every week. The soil should be moist, loose and well-drained. If over-watered, the soil will starve the roots of oxygen. Fertilize on a monthly basis throughout the growing season (April through November) with acid fertilizer. Don't over-fertilize though, as too much causes damage from salt accumulation. Prune in early spring for shaping and deadhead flowering to further encourage more flowering.

Pest Problems

Check shrubs periodically for aphids, Japanese wax scales, mealybugs and citrus white flies. Either evenly apply a horticultural oil (referred to as dormant, superior or 70-second oils) or an insecticidal soap to control these pests. Timing and application technique is crucial for either one of these pest control methods and may require multiple applications to be effective.

References

• Purdue University Consumer Horticulture: Gardenia: A Gardener's Challenge
• University of Rhode Island Landscape Horticulture Program: Gardenia Care Factsheets
• Iowa State University Extension: Using Horticultural Oil Sprays for Pest Control
• National Gardening Association: Gardenia
• Iowa State University Extension: Using Horticultural Oil Sprays for Pest Control

Resources

• Washington State University Extension: Guidelines for Insecticidal Soap
• The Garden Helper: Troubleshooting, Diagnosing and Resolving Plant Health Problems