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