How to Raise Cucumbers in a Greenhouse

Start the cucumber plants in a warm environment. The cucumber seeds germinate successfully when the temperature is about 85 degrees Fahrenheit. Place one seed in a 3 to 4-inch pot filled with soil or a soil-less growing medium. Plant the seed 1/2 inch deep. Cover the pot with a sheet of clear polyethylene to keep the temperature uniform and to avoid moisture loss. Remove the covering when the seedlings emerge from the soil in two to three days.

Provide 16 hours of light per day for the seedlings. In two to three weeks, the cucumber plants have three to four leaves and are ready to transplant to the larger greenhouse. Transplant the seedlings to 3-gallon pots or other greenhouse containers filled with soil or a soil-less planting medium. Sandy loam soil is one type of soil that successfully grows cucumber plants. Place the pots in rows and provide 6 to 8 square feet of floor space for each plant.

Run a heavy wire 7 to 8 feet above the row of pots. Suspend a piece of heavy sisal or polyethylene twine from the wire above each pot. Use a non-slip knot to attach the string to the base of the cucumber plant. Train the cucumber plant to grow up the string by attaching the stem to the string with plastic clips. Allow one stem per plant to develop and clip the lower plant leaves.

Perform a soil test on the soil or growing medium. Fertilize the cucumber plants according to the results of the soil test. Weekly feedings of a fertilizer with a grade of 20-20-20 is a common fertilizer program. Maintain a greenhouse temperature of 75 to 80 degrees during the day and at least 65 degrees at night. A cooler greenhouse results in slower growth and delayed cucumber production. A greenhouse that's too warm may affect cucumber quality.

Irrigate the cucumber plants with a drip or trickle system. Inspect the plants regularly for signs of pests or disease. Using a sterilized soil and clean pots reduces the chance of cucumber disease.

Harvest the cucumbers approximately 60 to 70 days after planting the seeds. A cucumber plant produces approximately 1 to 3 pounds of fruit per week or a total of about 25 cucumbers over a 10- to 12-week period.