Wheatgrass can be grown in tray systems, soilless systems or in individual planting trays available at your local garden center. The stacking tray system is sometimes covered with a plastic dome that creates a greenhouse effect, while soilless systems feature automatic watering systems that keep the sprouts moist at all times.
With the tray system, the seeds sprout in a growing medium, such as humus-rich potting soil, and are harvested when they are about 6 inches tall. The sprouts need indirect sunlight and enough water at all times to keep the soil damp but not soggy.
In all growing systems, harvest the wheatgrass sprouts by cutting them just above the soil line. According to Juicing for Health, a 21- by 11-inch tray should supply you with enough wheatgrass for about a pint of juice. Inexperienced juicers should limit their initial intake of wheatgrass juice to an ounce per day until they know how it will affect them.