Perhaps there is no better shrub to plant near a partially shaded deck or patio. Some people love the copious display of white flowers. Others adore the aroma. Still others appreciate the dark glossy foliage. Together with magnolias, crape myrtles and camellias gardenias are a symbol of the southeast. It’s a shame so many people have trouble getting them to thrive.
Known also as cape jasmine, gardenia (Gardenia jasminoides) requires acid but not extremely acid soil. Pretty much all cultivars also need soil that is neither too wet nor too dry. Sun is necessary for desirable flowering, but too much will stress them. Avoid locations with heavy afternoon sun.
Roots are also healthier if soil temperature doesn’t fluctuate much, so they benefit from heavy organic mulching. Planting flowers or ground covers around them can help if they have similar environmental tolerances.
Last winter was tough on gardenias. The problem generally was the result of prolonged wetness rather than extreme cold, but the reasons didn’t matter if yours died or were sick. Mine are just now starting to look healthy. I’ve tried to get gardenias to grow near my porch steps, but fluctuating moisture levels were a problem so I found another location.
Stress also makes gardenias more susceptible to insects and diseases. Many people experience black sooty mold covering much of the foliage. This black powdery substance isn’t the root of the problem. It is the result of insects such as mealybugs, aphids, tea scale or most likely whiteflies. All have sucking mouthparts that feed on plant sap. In turn, the insects generate this sweet sticky substance called honeydew. This sugary material makes great food for the fungus and the black mold thrives.
The mold generally doesn’t harm plants that much but it’s unsightly. It can be removed with a mild dishwashing detergent and a water hose. Several sessions may be necessary and late in the day is best to avoid plant injury.
Detergents as well as insecticidal soaps can also help control the insect pests. If more aggressive measures are necessary there are a few systemic insecticides available. Products containing pyrethrin, acephate or imidacloprid are effective.
Once your gardenias are healthy you can enjoy their beauty and aroma. They bloom from late spring through midsummer. Spend some time outside and treat your olfactory senses or cut a few blooms and float them in a bowl inside on the table. If you have abundant blooms you can take that a step further and make your own homemade gardenia perfume.
Extract the essential oil from mashed petals with alcohol (many use vodka). Strain the mixture through gauze or cheesecloth and dilute with water. Your perfume is now ready, but maybe best used as an air freshener or to sweeten up the pet’s bed.
Some people make tea from gardenia flowers. It has strong laxative properties. Yellow dye is made from fruits, which are used in Chinese medicine. I’ve never made gardenia tea, but flowers are great for corsages. They hold up well and provide a nice fragrance.
Ted Manzer teaches agriculture at Northeastern High School.
I moved into a new house (to me) last October. The house is about 20 years old. I suspect the gardenia bushes are from the original owners. They are over 6 ft. tall and about as wide. They have an abundance of blooms but very little fragrance. I have always had gardenias that had a very strong aroma. What makes the difference? I suspect from the appearance that these bushes have not been cut back in many year?
That could well be the case. Sometimes they are weakened by insect pests like white flies and that can affect their aroma too.