To grow, plants require specific ingredients: water, sunlight and carbon dioxide. Some plants need more than just these ingredients to survive, especially if they're living in harsh conditions where water is scarce. In certain situations, watering your plants with sugar water is beneficial to their growth.
During the process of photosynthesis, plants take in water, sunlight and carbon dioxide to produce glucose, or sugar, and oxygen. Plants use the sugar they create as energy to grow and carry out other life processes. They also store the sugar when it's not in use. Without the sugar they create, plants are unable to function and they eventually die.
Sugar is essential for plant growth. Adding sugar to water when feeding plants also helps retain moisture in their soil, preventing dehydration. Extra moisture is extremely beneficial to plants that experience dry conditions for lengthy periods of time. When watering plants with sugar water, base the amounts of sugar you use on the size and condition of the plant.
Adding large amounts of sugar to plant water will eventually kill the plant, especially if they're watered with sugar water on a frequent basis. This is because the added sugar affects the plant's natural ability to produce its own sugars. This excess of sugar also enables mould growth in the soil, due to the added moisture. Some plants experience positive reactions when watered with sugar water, while others experience adverse effects.
A test conducted by Mary M. Karcher at the California State Science Fair in 2005 concluded that bean plants actually benefited from being watered with sugar water. For 28 days, the bean plants were watered with 22.18ml of water in various amounts of sugar (no sugar, 25 grams of sugar per litre of water, 50 grams of sugar per litre of water and 75 grams of sugar per litre of water). At the end of the experiment, the plants watered with 50 grams of sugar per litre of water had the largest, healthiest roots.