We moved into our house two years ago and we had grass that was all green. Then last year we cut it down a little, it got only a few striped blades so I thought those were just diseaed leaves. Then this year we cut it even lower and now you can fully tell that it is Zebra Grass and very pretty. However it still has all green blades on the sides, the middle is the only Zebra Grass looking part. What causes this, from what I can see there is only this type planeted in that corner.