BuyWheatgrass.org is the best place to learn where to buy wheatgrass. Buy wheatgrass from the wrong source and you've wasted your money. It's essential to make sure that you get the highest quality, natural ingredients available when buying wheatgrass. This site is a collection of the best places to buy wheatgrass and all of the things related to wheatgrass.
Some people prefer to buy wheatgrass kits and try to grow their own wheatgrass, while others use wheatgrass powder and wheatgrass supplements. My personal preference is wheatgrass juice. I order from a company called DynamicGreens which is a frozen wheatgrass juice supplier. The prices may seem a bit high, but their juice concentrate goes a long way and is the purest wheatgrass juice that I've found. One of the biggest factors for me is their statement that their product has no detectable mold, which is a big issue for me. I once tried growing my own wheatgrass in a greenhouse and ended up with mold on the lower half of the grass. I went ahead and juiced it and then drank it for a few days. I became sick at my stomach very quickly. So, your best bet for nutrients with no side-effects is frozen wheatgrass juice, but if you choose to grow your own wheatgrass then be careful!
Whatever you do though, go ahead and make the decision to buy wheatgrass and implement it into your diet. The health benefits are amazing!