When arranging flowers in a vase, it's important to focus on providing the best conditions to prolong their freshness and vitality. While it may seem unusual, adding sugar or salt to the vase can actually be beneficial for the flowers. Sugar acts as a source of nourishment for the flowers, helping them to last longer. A small amount, about a teaspoon per vase, is usually sufficient. On the other hand, salt can help to prevent the growth of bacteria in the water, which can also extend the life of your flowers. However, it's important to only use a pinch of salt, as too much can have a detrimental effect on the flowers. A combination of both sugar and salt can be used to provide nourishment and prevent bacteria growth, but it's also recommended to change the water every two days to maintain freshness.