Spinach plants can easily withstand the cool temperatures of winter when placed in a sunny location indoors. A spinach plant can produce edible greens within 30 days of planting.
Prepare containers that are at least 6 inches in diameter by cleaning the containers thoroughly and filling them with a conventional potting soil. Spinach grows well in temperatures that range from 41 to 75 degrees Fahrenheit. If the spinach is placed near a sunny window, monitor the temperature and the amount of sunlight that the spinach plant receives. Too much sunlight may cause the plant to produce tough, bitter leaves. Apply a fertilizer, such as fish emulsion, to the plants each week until you harvest the spinach leaves. Water the plants when the top layer of the soil becomes slightly dry, and use a container with adequate drainage.
To grow spinach indoors during the winter, start seeds in a warm area, and cover the container with clear plastic to germinate the seeds properly. Remove the plastic cover, and place the plants in a sunny location after they sprout. During the winter months, greens may grow best when placed near a south-facing window. Spinach can be harvested several times throughout the winter by removing a few leaves from each plant. Allow the leaves to reach about 4 inches in length before harvesting, and then cut individual leaves from the plants with sharp scissors. Compost spinach plants after the last harvest, and reuse the container for a new crop.