Fertilize flowers and vegetables
Most of us fertilize our plants when we plant them. With short season vegetables that mature in 60 days or less, such as radish, spinach and leaf lettuce, that is probably adequate. Longer season vegetables and flowers need repeat fertilization. Containers need the most frequent fertilization because of lower soil volume and more rapid drainage and evaporation. One of the first signs that plants need additional fertilizer is when lower plant leaves turn yellow.
Osmocote and similar coated, slow release fertilizers are my favorite for containers. They are the longest lasting. General purpose fertilizers such as 16-16-16 work well for flowers and vegetables.
If you are irrigating your lawn, another application of lawn fertilizer will keep it green through the summer. I always recommend lawn fertilizers which contain part of the nitrogen in a coated or slow release form. Organic fertilizers are naturally long lasting.