Why Does Sugar Help Cut Flowers Live Longer?

Cut flowers are one of those simple pleasures that span time. From elaborate rose arrangements delivered by the florist to a wilted bunch of honeysuckle offered from a toddler's sweaty hand, flowers have the ability to delight. Once the flowers are separated from their root systems, the harvested portion undergoes physiological changes that can lead to early wilting unless they receive the nutrition they need.

Immature flower heads and blooms are often harvested commercially to prolong the life of the flower and to minimize mechanical damage from post harvest handling from field to home. In order for these immature flower heads to eventually open into spectacular blooms, they require carbohydrates (or sugars) stored in the stems or leaves of the plant. Cut flowers have the ability to mobilize these nutrients, but when harvested at a young age, these flowers may not have adequate amounts of stored nutrients. When carbohydrate levels are low, the opening flower petals may be pale and wilt prematurely. Sugar solutions can be added to the vase water at this point to supply the missing nutrients.

Most flowers benefit from a 2 percent sugar solution in their water. Some flowers do better with differing percentages of sugar. Gladioli do better with 4 to 6 percent, but zinnias and coral bells sustain damage from concentrations higher than about 1 percent sugar. Some other flowers do well without any sugar at all, such as chrysanthemums. A one percent solution of sugar can be approximated by dissolving 2 level teaspoons of sugar in 1 quart of water.

In sugar solutions, bacteria and other undesirable organisms are sure to follow unless preventative measures are taken. Adding a biocide to the water along with the sugar impedes unwanted microorganism growth. A common biocide, or a compound that inhibits bacterial growth, is household bleach. A 50 ppm (parts per million) solution of bleach and water will adequately inhibit growth. The 50 ppm solution can be obtained by mixing 1 ml of bleach with 1 quart of water. Measuring this small amount can be done using an eyedropper you can get from any pharmacy.

Another method of providing sugar to cut flowers is known in the commercial flower industry as "pulsing." In this method, flowers are packed in sugar overnight to allow them to take up the maximum amount of sugar possible. Not all flowers respond favorably to this method, so this is best left to the experts.

An easy sugary recipe to feed your flower guests consists of 1 can of non-diet citrus soda, 3 cans of water and 1.2 ml (1 - 1 1/2 eyedroppers) of bleach. The citrus soda contains citric acid, which has a low pH. Water with lower pH has been shown to travel faster in the vascular system of flowers, preventing or reducing wilting. A second recipe includes 2 tablespoons of fresh lime or lemon juice, 1/2 tablespoon of bleach, 1 tablespoon of sugar and 1 quart of water. Either solution should be made and used fresh daily.