sorry I just saw your question. About 4 times a year I think. It is slow release. and you can overwater grass, we now only water every 2 to 3 days for 3 minutes. I think every 3rd day is good for us, 4 is too long, but check the pots more often. I actually find that the when the flowers are gasping I water in horror that the poor things are gasping lol