Aeoniums need a balanced, slow-release fertilizer applied in the spring and summer months. Use a 10-10-10 or 20-20-20 water-soluble fertilizer at a rate of 1/2 teaspoon per gallon of water every two to four weeks during the growing season. Avoid fertilizing in the fall and winter when growth slows down. Over-fertilizing can burn the roots and lead to leaf drop. Always follow the manufacturer's instructions for proper application and handling of fertilizers.