Wheatgrass is used as a healthy juice or garnish for humans and as a snack for cats, who crave the taste of greenery. You can grow wheatgrass either in soil or water---many people choose the latter method because it isn't difficult and you don't have to worry about messy soil mixes. You can grow wheatgrass indoors anytime of the year and as often as you wish.
Find or purchase a tray large enough to contain the seed and the growing wheatgrass. It should be at least 4 inches deep to hold water and help support the grass when it grows. A deep, non-rusting baking tray would also work, or a plastic tray.
Place wheat seeds in a glass jar. Place your hand over the glass and shake it vigorously. Pour out the water, leaving the seeds. Repeat this process to rinse the seeds well.
Refill the container with fresh water and soak to initiate germination. According to sprouting.com, you should soak them between eight to 12 hours.
Dampen un-bleached paper towels and place two to three layers on the bottom of the tray. Pour the water out of the wheat seed jar and spread the seeds over the paper towels. Place a sheet of plastic wrap over this---do not seal it, just lay it loosely over the seeds.
Place the tray in a sunny area. Fill a spray bottle with water. Mist the seeds every day to keep them moist. When they've just begun sprouting, gently pour in enough water to drench the paper towels.
Add more water (sprouting.com suggests ½ cup if you are using a tray that is 11 by 21 inches) daily as the wheatgrass starts to grow---it only takes a few days to grow grass tall enough to cut and eat. You can remove the plastic wrap when they start growing and just keep the grass watered until you harvest it.