Geraniums should be fertilized regularly during their growing season, which is typically from spring to fall. Fertilizer should be applied every two to three weeks or as directed on the packaging. It is important to use a fertilizer that is specifically formulated for Geraniums, as they have unique nutrient requirements. The fertilizer should also contain balanced amounts of nitrogen, phosphorus, and potassium, with a ratio of approximately 1:2:1. When applying the fertilizer, be sure to follow the recommended dosage and avoid over-fertilizing, which can lead to excessive growth and reduced flower production. Water the plant thoroughly after fertilizing to ensure that the nutrients are absorbed properly.