There is no single "thatch grass" species. The term "thatch" refers to a layer of dead plant material that accumulates on the soil surface, and it can be formed by many different types of grasses.

If you are referring to a specific type of grass that is known to form thatch, you need to provide more information, such as:

* The type of grass: Is it a lawn grass, a wild grass, or something else?

* The location: Where does this grass grow?

* Any other identifying features: What does the grass look like?

Once you provide more details, I can help you identify the scientific name of the grass you're looking for.