Receiving flowers for a birthday, anniversary, Valentine’s Day, or "just because" is always nice. After someone gives you a beautiful bouquet of flowers, you probably cut the ends of the stems and put the flowers in a vase with water ... but what’s the purpose of that little square packet that comes with the flowers?
The packet contains powdered "flower food" that is meant to make your flowers last longer. Because flowers quickly age and droop after they’ve been cut, flower food provides nutrients to combat the rapid onset of wilting. Although specific ingredients vary depending on what type of flower food you get, most flower food packets contain sugar, acid, and bleach. Sugar gives nutrients to the flowers, acid maintains the pH level of the water, and bleach reduces the amount of bacteria and fungi in the water. Some flower food packets may also include stem unpluggers, a chemical (or chemicals) that prevent the stem from closing, ensuring that the flower can absorb the flower food and water.
Although you don’t have to sprinkle the packet of flower food into the water, studies have shown that doing so is one of the most effective ways to keep your flowers looking vibrant for as long as possible. If you accidentally throw out the packet of flower food, the Brooklyn Botanic Garden has instructions for making your own homemade flower food by mixing water with sugar, lemon or lime juice, and household bleach.
To ensure good-looking flowers, you can also sterilize the vase you’re using (you can disinfect it with bleach and water), change the water and trim the stems daily, and keep the flowers out of direct sunlight. Flower food packets are not one size fits all, so make sure to follow the directions printed on them.