The scientific classification of Trichocereus and Dudleya 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 Dudleya kingdom and all other plants kingdom is Plantaea.
Plant family is the group of plants which have something in common. Trichocereus and Dudleya family is a major factor of Trichocereus and Dudleya 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 Dudleya belongs to the family Crassulaceae.
While comparing scientific classification, Trichocereus and Dudleya genus and other classification are also important. Also, when you compare Trichocereus and Dudleya, 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 Dudleya. Trichocereus tribe is Trichocereeae and Dudleya tribe is Not Available. Trichocereus clade is Angiosperms, Core eudicots and Eudicots and order is Caryophyllales whereas Dudleya clade is Angiosperms, Core eudicots and Eudicots and order is Saxifragales. Every plant have subfamilies. Trichocereus subfamilies are, Cactoideae and Dudleya subfamilies are Not Available. In this way you can compare scientific classification of Trichocereus and Dudleya and other products also.