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