Miracle-Gro makes growing beautiful, vibrant houseplants easy with their Indoor Plant Food Spikes. Using the Miracle-Aerator spike, simply make a small hole in moist soil and insert the plant food spike. Then sit back, relax, and enjoy your happy houseplants. In spring and summer, spikes should be replaced every 30 days, while in winter and fall wait 60 days before replacing them. Miracle-Gro Indoor Plant Food Spikes are ideal for feeding all indoor plants, including ficus, snake plant, Croton, spider plants.