Epsom salt is not typically recommended as a fertilizer for gardenias since it lacks the nutrients that this plant needs to thrive. Instead, you can try feeding your gardenia with a high-potassium fertilizer or using compost tea to provide optimal nutrition. You may also want to consider planting a different type of gardenia if your current one is not performing well. Many other varieties can be more suitable for different growing conditions, so it's worth researching to find one that works best for your garden. With the right care and attention, your gardenia should be able to thrive and produce beautiful blooms year after year.