This unflavored carbonated beverage contains what are known as macronutrients. They are trace amounts of carbon, oxygen, hydrogen, phosphorous, potassium, sulfur and sodium, all elements necessary to healthy plant growth. These macronutrients are already dissolved within the club soda and are delivered directly to the plant's roots for swift and easy absorption.
In Danzell and Greenberg's study, plants offered club soda grew 170 percent of their starting height in a 10-day period, while those watered with tap water only showed a 67-percent growth rate. It was noted also that the plants given club soda were not only larger, but a deeper shade of green as well, which is indicative of vigor.
For best results, water your indoor and outdoor plants once a week with club soda. Water them following the same procedure you use when watering with tap water. Be sure you have drip pans beneath houseplants, as excess will still drain out just as with regular water.
It may be a good idea to alternate watering your plants with club soda and regular water to keep some of the minerals, like sodium, from building up in the soil. Club soda increases soil pH, which in turn affects plants' ability to absorb and utilize the minerals it offers. Nitrogen, phosphorus, potassium, magnesium and calcium are all made more available to a plant when the soil pH is above 5.8, but micronutrients such as iron and manganese may become less available.