Wheatgrass is the first stage of the same plant that eventually grows into the grain we use in bread and baked goods. Since we catch it in the first stage, it doesn't contain gluten (a protein found in the grains of wheat, barley and rye). At this stage, it is a vegetable - not a grain: it doesn't contain gluten. This means it is a safe food, even for those with wheat allergies. At this time, when it looks like common grass, it is harvested, juiced, and frozen.