Scientific Context

• When plants absorb moisture from the soil around it, the moisture seeps into plant cells. Porous plant cell walls let the moisture in for the purposes of extracting sugar and salt form the water. The sugar and salt is then stored in the plant cells for the roots, which need sugar in order to continue development deeper into the soil. Possibly, then, gardeners could add a small amount of table sugar to water to get better growth.
  
  

Effects on Plant Growth

• Adding table sugar to plant water is a favorite science fair project for elementary and middle school students, but there has been comparatively little peer-reviewed scientific research that looks at its effects on plant growth closely. The results of both, however, seem to confirm that adding table sugar to plant water does have an observable and positive effect on plant growth. Common practice among professionals would seem to confirm this; commercial florists, for instance, have long used sugar to supplement sugar deficiencies in flowers that for marketing reasons need to be cut before they are fully developed. Of course, plant growth and health are difficult to quantify by simple observation, but to the extent that plant health can be externally observed, watering plants with sugar water can result in plants that appear larger and healthier than those watered with water alone.
  
  

Microbial Concerns

• The chief concern for any gardener who wants to experiment with adding sugar to plant water is microbial growth. High sugar content creates the perfect conditions for bacteria, mold and other micro-organisms that can threaten the health and longevity of your plant. A common solution to this problem is to add a biocide such as household bleach or Physan to the water you use for your plants. A mixture of one milliliter bleach to one quart of water will yield a solution of 50 parts-per-million (ppm) bleach. Physan is more concentrated, so half of a milliliter of Physan will yield 100 ppm. Either mix is suitable for a wide variety of plants and flowers and can effectively inhibit microbial growth.
  
  

Sugar Content

• The exact proportion of biocide to water depends heavily on the type of plant you are growing and many other important factors. Gladioli, for example, respond well to a more sugar-rich solution (4 percent to 6 percent of water content) than do Zinnias or Coralbells, which prefer a 1 percent sugar solution and can actually be damaged by a more sugar-rich watering solution. Other plant types (Chrysanthemums, China Asters and others) respond well without adding sugar. Consult local gardening experts who are familiar with the soil conditions in your geographic area or, better yet, conduct your own experiments with different amounts of sugar to observe what fosters plant growth most effectively.