Pour the wheatgrass seeds into the bottom of the pie plate, covering it completely with one layer of seeds.
Remove the seeds from the pie plate and place in the bowl. Cover and allow to soak at room temperature for at least eight hours.
Pour potting soil into the pie plate, filling it halfway full. Mist with water to dampen the soil.
Drain the water from the wheatgrass seeds using a colander. Rinse thoroughly, then arrange the seeds in a single layer on top of the soil. Barely cover with more potting soil. Mist with water.
Place the pie plate on the base of the cake dome and put the cover on. Set the cake dome in a warm, brightly lit location. Do not place in direct sunlight.
Allow the wheatgrass to grow for seven days or until 6 inches tall.
Cut the wheatgrass with sharp scissors, 1 inch from the base. Use the wheatgrass immediately in a juicer, or store in the refrigerator.