How to Care for Florida Gardenia

Test your soil pH about six months before planting and apply 1 pound of elemental sulfur per 100 square feet to lower it by 1 point until it reaches between 5.0 and 6.5. Although you have to feed gardenias during active growth, if you don’t plant them in acidic soil, they will have nutritional deficiencies later, despite adequate fertilization.

Condition your soil with 3 to 4 inches of compost and work it in 12 inches deep, using a spade fork. Matured compost improves any soil type, but adding it to sandy soil, of which Florida has a lot, improves its permeability and drainage, and helps nutrients move into the gardenias’ roots.

Plant the gardenias in full sunlight or partial shade and space them 5 to 6 feet apart. Space the gardenias several feet away from concrete, such as sidewalks and house foundations when planting.

Mound the soil 3 inches high around the main stem about 4 to 6 inches away from it to form a dam, also known as a berm. Water the gardenias with 3 inches of water inside the berm after planting. Water the gardenias with 1/2 inch of water twice a week during the first six weeks after planting. Water the gardenias once a week with 1/2 inch of water thereafter. During droughts, water the gardenias at the same frequency, but double the amount of water. Always water the gardenias on the same day or days of the week.

Mulch around the gardenias with 2 to 3 inches of acidic mulch, such as pine needles, shredded oak leaves or shredded pine bark. Keep a distance of 2 to 3 inches away from the main stems when mulching.

Distribute 6.6 pounds of granular, acid-forming, slow-release, 15-5-10 NPK fertilizer per 1,000 square feet over the soil, using a broadcast spreader for the task. Fertilize the gardenias twice a year, in February and October if you live in south Florida, and in March and September if you live in north Florida. Fertilize an additional time in mid-summer in both north and south Florida if the gardenias are growing slowly.

Pinch off the tips of tender new growth in June and August of the first year to promote heavy branching.

Prune back all diseased, damaged or dead branches to healthy tissue as soon as you see them, using sterilized pruning shears for the job. Prune off spent flower heads immediately after flowering. Prune back all other branches, such as those vertically growing and tangled, in June or July. Prune back branch tips to shape the shrubs in June or July also.

Check the gardenias regularly for mealybugs, aphids, whiteflies and scales. Mealybugs resemble cottony white blemishes or masses where leaves connect attach to branches. Aphids have soft, white, green, brown or black bodies shaped like tear drops, measure between 1/16 and 1/8 inch long and congregate on the bottoms of leaves. Adult whiteflies look like miniature moths, and whitefly larvae measure about 1/8 inch long and have white bodies. Scales look like 1/16- to 1/8-inch-wide fuzzy bumps on leaves and stems.

Mix together 5 tablespoons of insecticidal soap containing 2 percent potassium salts of fatty acids with 1 gallon of water in a pump-type sprayer if you find aphids, scales, mealybugs or whiteflies on your gardenias. Spray the pests until well covered, and repeat once a week as needed. Don’t apply insecticidal soap when the temperature exceeds 90 degrees Fahrenheit to prevent scorching the leaves.