Which plants benefit fr coffee grounds?
Coffee grounds, contrary to popular believe, do not acidify plants or provide any special nutrients. It is best to add coffee grounds to your compost and use them this way. If you are trying to acidify your soil, there are products on the market that will give you better, and more consistent results. If you have leftover brewed coffee, you can water your plants with it (houseplants too) and this will add a touch of acidity. I would start with a soil test so you know what your soil pH is and if there are any nutritional deficiencies. A top-dressing of 2-3 inches of compost is often all that is needed for perennials and shrubs, roses being an exception. Look up [your state] Extension Service for soil test information.