I have been putting coffee grounds on my gardenia plant. How often can I do this. The plant sits indoors in an east window and I water it about every 5 to 7 days. It is sitting in a tray and I water it until the tray begins to fill. It is developing buds and has bloomed twice this month. It seems to like the coffee grounds but I do not know how often to use them.
Gardenias prefer acidic soil but used coffee grounds are not a good way to lower pH or to fertilize. Coffee beans vary widely in acidity and most of that acid leaches out into the liquid when coffee is brewed. The grounds don't significantly alter pH and don't provide nutrients so they are best added to the compost pile. Use a fertilizer designed for acid-loving plants and follow directions on the container. This will probably be every 2-4 weeks during active growth, depending on the fertilizer used. The effect will be more predictable than using coffee grounds to meet the plant's needs.