Grasses make up a huge group of plants with 500 genera and 10,000 species. They are also probably the most important plant family for food value. Corn, wheat, rice, and barley are all grasses that supply the majority of the world's food. Bamboo is also a grass that is important in infrastructure in S.E. asia.
Systematics: If you're trying to identify a grass, make sure you have a dissecting microscope and have someone nearby that knows what they are talking about because this group is very difficult as the flowers are about the size of pin-heads. They have alternating leaves that sheath the stem, but are overlapping (not connected). There are usually 3 but some have 6 stamens and there is usually a single 2-carpellate pistil.
Grasses are divided into major subfamilies. Two of the most common are the Festucoideae and Panicoideae. The Festucoideae have glumes that stay on the plant, more than one fertile flower (which has the first lemma fertile), and has glumes compressed side to side.
The Panicoideae have the first lemma sterile, and the second (and only) lemma fertile. The entire spikelet falls away from the inflorescence when it is done flowering.
Species list of invasive or problem plants