Gardenias are popular houseplants in the northern United States and are garden plants in Southern regions. A delicate plant, the gardenia requires special growing conditions, including special soil mix, to flourish and produce attractive blooms. Gardenia soil mix addresses the plant's need for correct pH, nutrition, moisture and drainage, while being easy for gardeners to prepare.
Gardenias, like azaleas and rhododendrons, require a soil that is slightly acid; that is, with a low pH. A soil test kit should verify whether a soil mix is adequately acid for gardenias. If it is not, adding peat moss to the soil mix will render it more acidic.
Gardenias require good drainage, so a soil mix for growing gardenias should not be heavy or contain too much clay. Feeling the soil mix will confirm whether it is light enough for good drainage. Peat moss is a good amendment for a soil mix that is too heavy. Perlite is also an available amendment, but is not environmentally sustainable, and is thus not used by some gardeners. Sand can be a good substitute for perlite, if used in small amounts.
Gardenias require rich soil, with ample nutrients. Adding timed-release fertilizer and coffee grounds to increase acidity and add nutrients is normally necessary to make a soil mix optimal for growing gardenias.
Mold-related problems are the No. 1 cause of damage to gardenias, or poor plant performance. For this reason, ordinary garden dirt is not suitable as a soil mix for gardenias. Dirt from outdoors can harbor many forms of mold that can cause diseases in a plant that grows in humid conditions, as a gardenia does.
Purchasing vs Creating Soil Mix
Amending an existing commercial potting mix to be suitable for gardenias is the most efficient option for most gardeners. Soil mix can also be created by combining rich commercially purchased topsoil with fertilizer, peat moss, sand or perlite, and compost.