Growing wheatgrass in a greenhouse requires monitoring so that the seed is kept moist and the humidity and temperature are not too high as to dry the grass as it grows. Wheatgrass is easy to grow in the greenhouse as long as you have the right location and supplies to make sure that the wheatgrass is planted the right way. Three points to remember about growing wheatgrass in greenhouses is humidity, air circulation and light.
Fill a quart jar with cold water. Place the wheatgrass seeds in the jar. Rinse the seeds, place a piece of paper towel over the opening, and pour out the water. Repeat this step once more.
Fill the jar with water one more time, and cover with the paper towel. Keep the seeds in the water for 12 hours. Drain the water using paper towel on the opening after they have sat in the water for the full 12 hours.
Pour 2 quarts of wheatgrass soil into one of the growing trays. (Genesis wheatgrass soil works the best). Move around with the hand to level off the soil. The soil should be 1/2-inch deep. Add more soil or remove soil to meet this need. Use the spray bottle filled with water to dampen the soil. Use your finger to test the soil to make sure that it is damp.
Sow the seeds on the top of the soil. Use the spray bottle to water the seeds and get them wet.
Use the second growing tray as the cover for the bottom tray. Use a small piece of wood or something similar to prop up one corner for ventilation.
Place the tray in an area of the greenhouse where the temperature is between 60 and 70 degrees F. The ideal location is out of direct sunlight where the humidity is high, but not more than 50 percent to 60 percent.
Water the wheatgrass at least twice a day until the blades are about 2 inches long, then remove the top tray. Use a mister if the air is too hot in the greenhouse to keep the blades moist. Keep the air circulating in the greenhouse so that humidity and temperatures don't wilt the grass blades.