Grasses are shallow-rooted perennials that have long, narrow leaves with veins running parallel to their length. Grasses, which are often herbs, typically grow in large masses, though some grasses, like bamboo, are large and woody.
Grass seed can grow just about anywhere, just as long as they have plenty of water and nutrients. Can grass grow on lava rocks as well as it can on soil, though? Find out the answer to this question in this article from HowStuffWorks.