Caring For Your Gardenias Plant gardenias where they will get morning sun and afternoon shade. Good air circulation is a must. Gardenias prefer moist, acid soil with good drainage & lots of organic matter. When planting, set the root-ball about 1" higher than the surrounding soil. Gently taper the soil up to the top of the exposed root-ball. Mulch. Pests (whiteflies, scales, & mealybugs). can be a problem. Control by applying a light horticultural oil to prevent sooty mold.