Which chemical when added to water can prolong the vase life of cut flowers?

A floral preservative is specifically designed to enhance the vase life of cut flowers. It typically contains a mixture of ingredients that serve multiple purposes: it provides essential nutrients to the flowers, suppresses microbial growth, and helps maintain proper pH levels in the water. The nutrients within the preservative, such as sugars, help the flowers maintain their vitality longer, while the antimicrobial agents prevent bacteria and fungi from clogging the stems, which can interfere with water uptake.

Other options listed have roles that may not be as effective for prolonging vase life. For example, while a hydrating solution can help hydrate flowers, it does not provide the essential nutrients that a floral preservative does. Citric acid can help in some contexts, particularly in adjusting pH or acting as a sour agent, but it is not a complete solution for extending flower longevity. A water softener can modify water hardness, but it does not address the specific needs of cut flowers for nutrients and microbial control, making a floral preservative the most effective choice for prolonging the vase life of cut flowers.