Many people are intoxicated by the unmistakable fragrance of gardenias and are awed by the plant’s beautiful blossoms. Gardenia jasminoides is a semitropical beauty that grows best in a warm, humid atmosphere and in an area that offers an abundance of sunlight. In the garden, the plant is hardy in zones 8-10. In all other areas, it’s treated as a houseplant.

Gardenia close up

Who can resist the intoxicating fragrance of the gardenia?

Photo Credit: Donna Moramarco

Gardenia flower bud

This healthy gardenia bud is ready to open.

Photo Credit: Donna Moramarco

Gardenia standards

Make a statement – add a gardenia standard to your summer pots.

Photo Credit: Donna Moramarco

Potted Gardenia

Gardenia foliage has a waxy texture.

Photo Credit: Donna Moramarco

No matter where they’re grown, gardenias like acidic, moist, yet well-drained soils. But be careful: The biggest problem gardeners have with gardenias is usually overwatering. Doing so can cause foliage to yellow; so allow the soil to remain evenly moist, but not saturated. (Never allow the plant to become dry.) For potted houseplants, insert your finger at least 2 inches into the soil to check for wetness. If it feels moist to the touch, do NOT water. Ample humidity is also important. You can increase the amount of available humidity to your indoor gardenias (and other plants) by placing them on a pebble tray. Just fill a tray with clean pebbles, stones or gravel and set your houseplants on top of the pebbles. Keep the area filled with water, but do NOT let your houseplants sit in it.

If you live in USDA Hardiness Zone 7 or colder, your indoor gardenias can enjoy the summer months outside (from June 1 to Sept. 1). Just be sure to locate your plants away from intense, direct sunlight. (Filtered bright light is best.) If you want, sink the pot to the rim in the soil. Be sure to keep up with your watering practices as outlined above!

It’s time for a few words about indoor temperatures and gardenias: If you’re growing them indoors, a southern exposure where temperatures are in the 70-degree-F range during the day is best for the winter months. The night temperature should range between 62-65 degrees F. If temperatures are lower than this, the plants will grow slowly and the foliage is likely to turn yellow-green. Nighttime temperatures above 65 degrees F are partially responsible for the buds dropping – a common difficulty with gardenias. In addition, higher temperatures encourage vegetative growth at the expense of flower buds.

Yellowing foliage can be caused by factors other than low temperature and overwatering. A deficiency of iron in nonacid soils will also cause this yellowing symptom. This can be corrected by adjusting the soil pH – gardenias prefer a pH range of 5-6. (Have a soil test done to find the existing pH of your soil.) An acid-base houseplant fertilizer can be used to lower the soil pH for your indoor plants.

Occasional fertilizing with a complete acid-base fertilizer containing nitrogen, phosphorus and potassium will give your gardenias a needed boost. Be certain to follow the directions on the fertilizer container for frequency and rate of application. Avoid fertilizing between November and February.

When it comes to pests, controlling insect problems on any plant can be a challenge, and gardenias are no exception. Mealybugs are the most prevalent gardenia pest. They’re easily identified as white cottony masses found in the leaf axils and other protected areas of the plant, making the pest difficult to control. Scales can also be a problem, which can appear as raised brown bumps on the stems and underside of leaves. Aphids, too, can be troublesome to gardenias. These soft-bodied, tear-shaped insects can be found clustered around newer growth and/or on the underside of leaves. And nematodes – minute worm-like organisms – work inside the roots and produce swollen, knotted areas. (Yellow foliage may later result.)

In controlling these pests, your best approach is to have your problem properly identified BEFORE you apply any control at all. It’s important to know what the insect is, the best time to control said insect and what control is most effective. This all follows the strategies of integrated pest management, or IPM. If pesticides are used in your strategy, make sure they’re properly applied according to the label directions.

Dealing with diseases on gardenias can be a challenge as well. Powdery mildew can be a problem in indoor areas where there’s poor air circulation and/or excessive moisture on the foliage. Consider improving the air flow and never mist the plant if powdery mildew is present on the leaves or buds. Leaf spots, either fungal or bacterial, can cause gardenias trouble, too. Again, avoid excessive moisture and areas of poor air circulation. As with pest control, your best approach to controlling diseases is to have your problem identified before any control is applied.

As for general maintenance, pruning may be needed from time to time to keep your gardenias bushy and compact. Removing old wood is a good practice to follow. If your plant looks somewhat tired and leggy, a severe “haircut” may be in order. Do this in early spring. Follow through with an application of fertilizer to replenish the vigor of the plant.

Are you ready to take the gardenia challenge? If so, you’ll be rewarded with intriguing flowers sure to intoxicate!