5 Ways to Kill a Gardenia

Avoid these garden blunders to keep this Southern favorite blooming.

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Photo By: Image courtesy of Lynn Coulter

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Avoid Gardenia Homicide

No one wants to kill a gardenia. Their creamy-white blossoms, so richly perfumed, are garden favorites, especially in the South. In colder climates, gardenias are popular as houseplants. But gardenias can be fragile and even demanding, and you often need a few tricks under your gardener’s hat to keep them happy and thriving. Watch out for these common pitfalls when you’re planting these beauties.

1. Neglect to test your soil before you plant.

Problem: Gardenias don’t like high pH soils, which can prevent their roots from absorbing iron, magnesium and other minerals they need for healthy growth. 

Solution: Test your soil before you plant and adjust the pH to a range of 5.0 to 6.5. Soil test kits are available from many garden centers and home improvement stores, or you can usually send a small soil sample to your local extension service office and tell them what you want to grow. 

If you’ve already planted without testing the soil, and your gardenia leaves start turning yellow, that’s usually a sign of chlorosis, which means your plant is starved for iron, vital in helping plants make chlorophyll. To treat it, add water-soluble sulfur or aluminum sulfate to the ground about 3 feet away from the plant. As an alternative, add chelated iron to the soil or directly to the leaves. Once the pH of the soil is adjusted, keep it in the proper range by using a slow-release fertilizer for acid-loving plants.

2. Cultivate around your gardenias often and deeply.

Problem: Gardenias prefer to be planted high in the ground, like azaleas and rhododendrons, so dig a hole only as deep as the plant’s root ball. Don’t hoe closely or deeply around them, to avoid damaging the roots. 

Solution: Mulch around the plants to help control the weeds, or hand-pull them.

3. Keep gardenias in your nice, dry house.

Problem: Gardenias need protection from cold winter temperatures, but they don’t do well indoors when the air is dry. That’s when whiteflies, mealybugs and mites can become real pests. 

Solution: Grow your plants in a room where the temperature ranges from 55 to 75 degrees F. Raise the humidity by growing them in pots atop trays filled with pebbles and water, or by using a humidifier, or by misting them. If pests appear, try knocking them off with a spray of water in the kitchen sink. If that doesn’t work, use an insecticidal soap, horticultural oil, or system insecticide. Read the manufacturer’s label to be sure the product you’re using treats your specific problem.

4. Skip the watering routine.

Problem: Gardenias need at least an inch of water a week, whether from rainfall or a hose. 

Solution: Again, use mulch to a depth of two to four inches to help keep moisture in the soil and control water-hogging weeds. Don’t let the plants become completely dry before you water, and water regularly. If you’re inconsistent, the buds and leaves may drop off.

5. Grow your gardenias in the shade.

Problem: Gardenias need bright light to set their blooms and produce those handsome, glossy leaves.

Solution: Grow gardenias in full sun in your garden spot, but if possible, give them some afternoon shade in hot weather and hot climates. If you’re growing them indoors, provide plenty of bright light, but keep them out of hot, direct sun.

Gardenias can be a challenge, but these familiar favorites are worth the work.

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