Growing a potato in water is primarily a method of pre-sprouting, known as chitting, which gives the tuber a head start before planting into soil. This technique is often used as a visual experiment or to shorten the time between planting and harvest. The potato, a modified underground stem called a tuber, contains the necessary starch reserves to kick-start its own growth. Placing the tuber in water encourages the rapid development of both roots and shoots, accelerating the natural growth cycle out of dormancy.
Preparing the Seed Potato and Water Setup
The process begins with selecting a healthy potato that has visible “eyes,” the dormant buds from which new growth will emerge. If a large potato is used, cut it into pieces, ensuring each section contains at least one or two prominent eyes and enough surrounding flesh for energy storage. Allow the cut surfaces to dry and form a protective layer, or “callus,” for a day or two to help prevent rot once the potato is placed in water.
To suspend the potato, insert three or four wooden toothpicks horizontally around its middle, spaced evenly to act as supports. Push the toothpicks in far enough to be sturdy, creating a cradle for the tuber on the rim of a glass or jar. This setup allows the bottom portion of the potato, typically the end with the most concentrated eyes, to be submerged in water while the rest remains exposed to air.
Fill the vessel with plain tap water until the lower half of the potato is completely immersed. This submerged section initiates initial root growth, drawing moisture directly into the tuber’s tissues. Maintain the water level, ensuring the surface of the potato does not dry out, which would inhibit the development of roots and sprouts.
Monitoring Sprout and Root Growth
Once the potato is suspended in water, place it in a location that receives bright, indirect light. Direct, intense sunlight is too harsh and can promote excessive algae growth or cause the potato to overheat. The optimal temperature for sprouting is between 60 and 70 degrees Fahrenheit, which encourages steady, robust growth.
Change the water every two to three days to prevent the build-up of bacteria and mold, which can cause the potato to rot. Clear or cloudy water signals that a refresh is needed, as the potato requires oxygen to respire. In a successful setup, small white rootlets will begin to emerge from the submerged surface within one to three weeks.
Simultaneously, sturdy, short sprouts will grow upward from the eyes exposed above the water line. These sprouts should be firm and dark green or purplish, indicating they are hardened and ready for planting. If the sprouts are long, pale, and spindly, the potato needs more light, as it is stretching to find a stronger source.
Moving the Sprouted Potato to Soil
The temporary water arrangement serves its purpose once the potato has developed a strong root system and robust sprouts. The tuber is ready for planting when the roots are approximately one to two inches long and the sprouts are sturdy and about a half-inch to an inch in length. Potatoes cannot thrive long-term in water alone, as they require the nutrients and physical support provided by soil.
When transplanting, handle the delicate water-grown roots with care to prevent breakage and minimize transplant shock. Plant the sprouted potato in a container or garden bed with well-drained, loose soil, such as a mix of potting soil and compost. Bury it approximately three to four inches deep, with the sprouts pointing upward toward the soil surface.
As the plant continues to grow, a process called hilling is necessary to encourage the formation of new tubers and protect existing ones from light exposure. When the green shoots reach about six to eight inches tall, mound soil up around the base of the plant, leaving only the top leaves exposed. This action creates a longer underground stem area where new potatoes will develop, maximizing the potential harvest.