Coffee grounds are not typically recommended as fertilizer for gardenias since they lack many essential nutrients that this plant needs to thrive. However, using coffee grounds as compost around your gardenia plant may help to improve soil quality and provide some beneficial nutrients. To maximize their effectiveness, mix them well with the surrounding soil. Additionally, you can add other organic matter to your gardenia bed, such as compost or manure, to help provide the nutrients your plant needs for optimal growth and blooming. With the right care and attention, your gardenia should be able to thrive and bloom beautifully year after year.