We asked Dr. Ku for her insight on cat grass.
Dr. Ku replied, "There are a variety of explanations that have been posed for why cats (and dogs) seem to eat grass. Some believe that it is a sign if gastrointestinal problems and one way to initiate vomiting. This could include anything for mild indigestion, inflammatory bowel problems, or a way to reduce heavy intestinal parasite loads in the “wild.” Others believe it could be they just like grass, despite not really needing it nutritionally. My own observation of my own cats/dogs has been that they seem to really like fresh grass at certain times of the year, especially early Spring when it is fresh and green, and likely soft. ..perhaps it’s a sign of Spring and they are celebrating? 😉 Regardless, it is clearly a thing, because pet stores actually sell grass you can buy to grow for your indoor pet. A few things to keep in mind if you want to indulge your cat’s wishes to eat grass. First of all, it is important to avoid letting them eat grass that has been treated with fertilizer or herbicide. Secondly, be prepared because often cats that eat grass will then vomit afterwards. If this is ok with you, then growing your own indoor, untreated grass that is young and fresh for them is probably a good way to go. As far as “Does your kitty need greens in her diet?” The answer is, “No.” Also, be sure your kitty is not one with gastrointestinal problems that should be addressed in other ways. Typically, it is not normal for cats to vomit too often. Once every 2-3 weeks is probably as often as I would consider normal. More than that is probably too often, and may be symptomatic of a health issue that could worsen if not addressed."
Check out these cat grass garden tips from The Humane Society website: