Pygmy Chain Sword will spread like a weed. I wouldn't exactly call it grass like, but still think it looks nice. It's a small version of an Amazon Sword where many leaves will grow from the center, called the crown.
It will send runners out over the top of the substrate and make several new plants as they creep around. Here is a picture of how it is doing in my own tank. The two pictures are 1 week apart. Results will obviously vary between tanks, no two is exactly the same so I can't say how it will do in your tank.