Apply a 2–4 inch (5.1–10.2 cm) layer of organic mulch to the gardenias. Mulch is made of decayed organic matter, such as leaves, bark, or compost and can be purchased at most gardening stores.
Mulch not only enriches soil, it will keep your soil moist, reduce the growth of weeds, and maintain a constant soil temperature.
For the best outcome, select a mulch made of wood chips, sawdust, or ground bark.
Applying mulch is extremely important since gardenia roots are shallow, making them especially vulnerable to weeds.[9]