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