To keep gerberas in a box fresh, it is important to follow some basic care. First, make sure to cut the stems diagonally before placing them in fresh water. Change the water every two days and add a floral preservative if possible. Keep the flowers in a cool place and avoid exposing them to direct sunlight or drafts. With these care steps, gerberas can stay vibrant and beautiful for longer, allowing you to enjoy their beauty for days.