Proponents of the tonic benefits of wheatgrass claim that the critical enzymes in the juice of its leaves only survive three hours or less after harvest. To be sure of getting the best possible product, grow your own wheatgrass and process the leaves yourself. Any variety of winter wheat suitable for sprouting into wheatberries develops the green leaves of wheatgrass after a week of proper growing conditions. Many health food stores and groceries sell the wheat grain needed for home windowsill gardens.
Select hard red winter wheat seed for the wheatgrass planting. Hardy winter wheat sprouts at temperatures of at least 60 degrees Fahrenheit and grows well at normal room temperatures. Temperatures over 90 degrees Fahrenheit stall the plant's growth.
Place 1 lb. of winter wheat seed in a mixing bowl. Add enough room-temperature water to fill the bowl 2 inches above the wheat.
Drain off the water after 8 hours. Rinse the wheat until the runoff clears.
Fill the window-box planter with potting mix at least 11/2 inches deep. Water the potting mix well. Stir the potting soil to eliminate any dry spots and then even out the soil in the planter.
Spread the seeds carefully in a uniform layer over the damp potting mix. Add another 1/2 inch of potting mix over the top of the seed layer. Water just enough to dampen the new layer of soil. Cover the top of the planter with a sheet of newspaper.
Water lightly each day. Remove the newspaper cover after three days when sprouts grow 2 inches tall. Place the planter in indirect light, not in direct sunlight, to stimulate production of chlorophyll in the leaves.
Harvest wheat grass when 7 or 8 inches tall by clipping the leaves 1 inch above the soil surface. Rinse the fresh leaves well in clean water before running them through the juicer.