The scientific classification of Trichocereus and Saguaro 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. Trichocereus and Saguaro kingdom and all other plants kingdom is Plantaea.
Plant family is the group of plants which have something in common. Trichocereus and Saguaro family is a major factor of Trichocereus and Saguaro 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. Trichocereus belongs to the family Cactaceae and Saguaro belongs to the family Cactaceae.
While comparing scientific classification, Trichocereus and Saguaro genus and other classification are also important. Also, when you compare Trichocereus and Saguaro, other factors should also be taken into considerations like order, subfamilies, tribe, clade etc. First plant's genus is Echinopsis and other plant's genus is Carnegiea. Trichocereus tribe is Trichocereeae and Saguaro tribe is Pachycereeae. Trichocereus clade is Angiosperms, Core eudicots and Eudicots and order is Caryophyllales whereas Saguaro clade is Angiosperms, Core eudicots and Eudicots and order is Caryophyllales. Every plant have subfamilies. Trichocereus subfamilies are, Cactoideae and Saguaro subfamilies are Cactoideae. In this way you can compare scientific classification of Trichocereus and Saguaro and other products also.