The scientific classification of Oatgrass and Trichocereus includes the entire classification chart that includes kingdom, family, clade, tribe etc. A kingdom is the second highest taxonomic rank. A taxonomic rank is the level that a living organisms are placed in hierarchical level of arrangement of life forms. All the living organisms are divided into kingdoms. Plant kingdom is a main classification of living organisms that include all plants. There are six kingdoms which are: Plantae, Animalia, Fungi, Protista, Aschaea/Archaeabacteria and Bacteria Eubacteria. Oatgrass and Trichocereus kingdom and all other plants kingdom is Plantaea.
Plant family is the group of plants which have something in common. Oatgrass and Trichocereus family is a major factor of Oatgrass and Trichocereus Scientific Classification. Plant family helps you narrow the search of your plants. It also gives you idea about, how the plant looks, how the seed will be like etc. These two plant families can be different or same. Oatgrass belongs to the family Poaceae and Trichocereus belongs to the family Cactaceae.
While comparing scientific classification, Oatgrass and Trichocereus genus and other classification are also important. Also, when you compare Oatgrass and Trichocereus, other factors should also be taken into considerations like order, subfamilies, tribe, clade etc. First plant's genus is Danthonia and other plant's genus is Echinopsis. Oatgrass tribe is Aveneae and Trichocereus tribe is Trichocereeae. Oatgrass clade is Angiosperms, Commelinids and Monocots and order is Poales whereas Trichocereus clade is Angiosperms, Core eudicots and Eudicots and order is Caryophyllales. Every plant have subfamilies. Oatgrass subfamilies are, Danthonioideae and Trichocereus subfamilies are Cactoideae. In this way you can compare scientific classification of Oatgrass and Trichocereus and other products also.