The scientific classification of Rhubarb and Petunia 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. Rhubarb and Petunia kingdom and all other plants kingdom is Plantaea.
Plant family is the group of plants which have something in common. Rhubarb and Petunia family is a major factor of Rhubarb and Petunia 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. Rhubarb belongs to the family Polygonaceae and Petunia belongs to the family Solanaceae.
While comparing scientific classification, Rhubarb and Petunia genus and other classification are also important. Also, when you compare Rhubarb and Petunia, other factors should also be taken into considerations like order, subfamilies, tribe, clade etc. First plant's genus is Rheum and other plant's genus is Petunia. Rhubarb tribe is Not Available and Petunia tribe is Not Available. Rhubarb clade is Angiosperms, Core eudicots and Eudicots and order is Caryophyllales whereas Petunia clade is Angiosperms, Asterids and Eudicots and order is Solanales. Every plant have subfamilies. Rhubarb subfamilies are, Not Available and Petunia subfamilies are Petunioideae. In this way you can compare scientific classification of Rhubarb and Petunia and other products also.