Cucumbers are part of a family of vegetables known as cucurbits, which, according to Purdue University, grow most effectively when days and nights are warm. Due to this requirement, cucumbers cannot be grown outdoors in winter in most of the continental U.S. So if you don't live the the country's warmest zones – South Florida, Hawaii and some parts of Southern California,, you must set up an indoor growing system to grow cucumbers in winter.
Plant each cucumber plant in a separate container that is at least 12 inches in diameter. If you use ground soil (which is not recommended), mix it with compost, peat moss or manure to create better drainage. Potting mixes provide a better source of nutrients and drainage for cucumbers and eliminate the possibilities of infestation from the insects in ground soil. Fill each container with the soil and press five to six cucumber seeds down into the center of the pot, approximately ½ inch deep.
Water each plant until the soil in the container is thoroughly moist and cover the container with plastic wrap, taping the plastic to the sides of the container or using a rubber band to hold the plastic in place. Put the cucumber plant in a warm place where it gets direct sunlight for six to eight hours per day or provide the plants with a grow light for the same length of time.
Keep newly planted cucumbers warm at all times. If the temperature in your greenhouse does not stay constant at night, install a heater and keep the temperature at 70 degrees or higher to help the cucumbers germinate and grow.
Take the plastic wrap from each cucumber container when the seedlings appear. Allow the seedlings to grow to 1 to 2 inches and weed out all but the strongest two growers. When these two seedlings get approximately 8 inches tall, cut away the weakest of the two seedlings and keep the strongest. Use scissors to remove seedlings to avoid disturbing the selected seedling's roots.
Continue to provide the cucumber seedlings with six to eight hours of daily light and water cucumber plants as often as necessary to keep the soil moist. After four to six weeks of growth, fertilize cucumber plants using your chosen fertilizer, whether chemical or organic, once a week following packaging recommends.