The scientific classification of Tree-of-Heaven and Gardenia 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. Tree-of-Heaven and Gardenia kingdom and all other plants kingdom is Plantaea.
Plant family is the group of plants which have something in common. Tree-of-Heaven and Gardenia family is a major factor of Tree-of-Heaven and Gardenia 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. Tree-of-Heaven belongs to the family Simaroubaceae and Gardenia belongs to the family Rubiaceae.
While comparing scientific classification, Tree-of-Heaven and Gardenia genus and other classification are also important. Also, when you compare Tree-of-Heaven and Gardenia, other factors should also be taken into considerations like order, subfamilies, tribe, clade etc. First plant's genus is Ailanthus and other plant's genus is Gardenia. Tree-of-Heaven tribe is Not Available and Gardenia tribe is Gardenieae. Tree-of-Heaven clade is Angiosperms, Eudicots and Rosids and order is Sapindales whereas Gardenia clade is Angiosperms, Asterids and Eudicots and order is Gentianales. Every plant have subfamilies. Tree-of-Heaven subfamilies are, Not Available and Gardenia subfamilies are Ixoroideae. In this way you can compare scientific classification of Tree-of-Heaven and Gardenia and other products also.